INDUSTRIAL ECOLOGY E S A

INDUSTRIAL  ECOLOGY E S A
Ylva Magnusson
ENVIRONMENTAL SYSTEMS ANALYSIS FOR
UTILISATION OF BOTTOM ASH IN GROUND
CONSTRUCTIONS
SUPERVISORS:
BJÖRN FROSTELL
ERIK KÄRRMAN
SUSANNA OLSSON
STOCKHOLM 2005
Master of Science Thesis
at
INDUSTRIAL ECOLOGY
ROYAL INSTITUTE OF TECHNOLOGY
www.ima.kth.se
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Abstract
Abstract
To decrease the disposal of waste and to save natural resources, several political initiatives
have been initiated both in Sweden and at a European level. Therefore an urgent task is to find
suitable utilisation areas for residuals, such as construction materials. For residual products to
be an interesting alternative to conventional aggregates, such as sand, gravel or crushed rock,
it is important that the material is environmentally acceptable. So far, environmental
evaluations of residuals mainly have focused on measurements of total chemical content and
leaching behaviour. The result has been that the positive effects, like for example less disposal
of material and reduced extraction of natural aggregates, not have been considered in the
evaluations. At the Royal Institute of Technology (KTH) in Stockholm, a method that uses a
broader system perspective has been developed. The method is based on an Environmental
Systems Analysis (ESA) approach and can act as a complement to the current leaching test.
The method has been used for studying the difference in environmental impacts that can be
expected if bottom ash from municipal solid waste incineration (MSWI) is used in road
construction or is disposed of. This study contributes with an expanded set of scenarios for
application of the MSWI bottom ash and with an improvement of data quality for disposal of
material. The new application of MSWI bottom ash is its use as a drainage material in
covering structures in a landfill.
The thesis showed that leaching of metals, resource use and emissions to air were the
environmental flows that were of most importance for assessing the environmental impact of
the studied scenarios. The use of MSWI bottom ash in road construction was found to be the
most environmentally preferable alternative, compared to utilisation of the MSWI bottom ash
as drainage material in a landfill structure or disposal of the ash. None of the applications
were free from negative environmental impact and different categories of impact were
dominating in the different applications. However, these results are strongly dependent on the
chosen system boundaries. The results are sensitive to changes in parameters such as transport
distance and the conditions affecting leaching, for example the amount of precipitation.
Besides these results, new life cycle data for disposal of material is presented in the study.
Previous data for the environmental impact from disposal of material were old and lacked
important information, such as the environmental impact related to covering structure in the
landfill. The ESA approach allowed both resource use and emissions to be considered and can
therefore be seen as valuable complement to other studies that use a narrower system
perspective. The results can be used to improve information for decision support concerning
waste management.
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Sammanfattning
Sammanfattning
Både på europeisk och svensk nivå finns politiska drivkrafter för att öka återvinningen och
återanvändningen av avfall och på så vis minska mängden avfall som förs till deponi. Det ses
därför som en angelägen uppgift att finna lämpliga sätt att återanvända restprodukter,
exempelvis som konstruktionsmaterial. För att restprodukter överhuvudtaget ska vara ett
alternativ till konventionella material såsom sand, grus eller bergkross är det viktigt att
miljöbedömningar av materialet görs. Hittills har debatten om användningen av restprodukter
präglats av ett snävt systemperspektiv, där man framförallt fokuserat på materialens
utlakningsrisker. Positiva effekter i form av exempelvis minskad deponering och minskad
naturresursutvinning har inte beaktats i samma utsträckning. Vid KTH i Stockholm har en
metod utvecklats som har ett bredare systemperspektiv, vilket kan ses som ett komplement till
dagens fokusering på utlakningsrisker. Metoden baseras på ett miljösystemanalysperspektiv
och i de pågående studierna har man studerat skillnaderna i miljöeffekter som uppstår då
bottenaska från avfallsförbränning används vid vägbyggnation eller deponeras. Den här
studien syftar till att utvidga metoden med ännu ett alternativ av nyttiggörande av
avfallsbottenaska, nämligen som dräneringsmaterial vid deponitäckning, samt förbättra
kvalitén på livscykeldata för deponering av material.
Tre viktiga aspekter för att bestämma miljöpåverkan visade sig vara utlakning av metaller från
materialen, resurshushållning samt utsläpp till luft från energianvändningen. Resultatet visade
att alternativet att använda askan vid vägbyggnation är att föredra i jämförelse med att
använda askan som dräneringsmaterial vid deponitäckning eller att deponera askan. Inget
alternativ i studien var dock fritt från miljöpåverkan och skilda typer av miljöpåverkan
dominerade i de olika alternativen. Resultat från studien visade sig vara känsligt för
förändring av transportavstånd och parametrar som påverkar utlakningen, exempel mängden
regn. Dessa resultat ska dock ses mot bakgrund av de systemgränser som valts och de
antaganden som gjorts i metoden. Vid sidan om dessa resultat presenteras nya livscykeldata
för deponering av material som tagits fram i studien. Tidigare existerande värden för
deponering av material var inaktuella och ofta var inte alla påverkande parametrar som
exempelvis sluttäckning av deponin inkluderade. Examensarbetet visar att miljösystemanalys
som metod inte bara beaktar utlakningsrisker vid miljöbedömning av omhändertagande av
restmaterial utan tar även hänsyn till resursförbrukning och emissioner. Denna typ av
riskbedömning kan exempelvis användas i beslutsunderlag för avfallshantering på regional
nivå.
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Preface
Preface
This report is a Master thesis and is the last element in the Master of Science programme –
Environmental Engineering and Sustainable Infrastructure at the Royal Institute of
Technology (KTH) in Stockholm. The study has been carried out at the Department of
Industrial Ecology in co-operation with the Department of Land and Water Resources
Engineering.
This thesis is one of two case studies in the project Environment systems analysis for the use
of residuals – A regional perspective on the utilisation of ashes in ground construction (Q
248). The project is financed by Värmeforsk (Thermal Engineering Research Institute) and is
lead by the consulting company Ramböll Sverige AB in co-operation with the department of
Land and Water Resources Engineering at KTH, the consulting firm Ecoloop and ÅF Energi
& Miljö AB.
Susanna Olsson, department of Land and Water Resources Engineering, KTH, and Erik
Kärrman, Ecoloop, were supervisors and Björn Frostell, department of Industrial Ecology,
KTH, was examiner for the thesis.
Finally I would like to express my appreciation to my supervisors and examiner for their
heartfelt assistance during my work.
Ylva Magnusson
Stockholm, February 2005
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Table of contents
Table of contents
1. Introduction ______________________________________________________5
2. Objectives ________________________________________________________5
3. Production of ashes ________________________________________________6
3.1 Coal and peat - bottom and fly ash _____________________________________________ 7
3.1.1 Utilisation of peat and coal ash ______________________________________________________ 7
3.1.2 Examples of projects where coal and peat ash have been used ______________________________ 7
3.2 MSWI bottom and fly ash _____________________________________________________ 9
3.2.1 Utilisation of MSWI ash ____________________________________________________________ 9
3.2.2 Examples of projects where MSWI ash have been used___________________________________ 10
3.3 Biofuel - bottom and fly ash __________________________________________________ 11
3.3.1 Utilisation of biofuel ash __________________________________________________________ 12
3.3.2 Examples of projects where biofuel-ash has been used ___________________________________ 13
3.4 Examples of the use of fly ash independent of origin ______________________________ 14
4. Environmental Systems Analysis (ESA) ______________________________14
4.1 Previous studies in the area of ESA for waste management ________________________ 16
5. Method __________________________________________________________17
5.1 Part 1 - Inventory of ashes in Uppsala County ___________________________________ 17
5.1.1 Ashes in Uppsala County and their potential use _______________________________________
5.1.2 Selection of ash _________________________________________________________________
5.1.3 Selection of utilisation scenarios ____________________________________________________
5.1.4 Description of the chosen scenarios__________________________________________________
17
17
18
19
5.2 Part 2 - ESA for different possible uses of MSWI bottom ash ______________________ 21
5.2.1 General description of the method - ESA for the use of residuals in a regional perspective _______
5.2.2 System boundaries and functional unit _______________________________________________
5.2.3 Inventory ______________________________________________________________________
5.2.4 Analysis of the result and Impact Assessment __________________________________________
21
22
23
27
6. Result ___________________________________________________________27
6.1 Result part 1 - Inventory of ashes in Uppsala County _____________________________ 27
6.2.1 Environmental flows connected to the 15 environmental quality objectives ___________________
6.2.2 Differences in resource use and emissions_____________________________________________
6.2.3 Use of natural aggregates _________________________________________________________
6.2.4 Leaching of metals _______________________________________________________________
6.2.5 Energy use _____________________________________________________________________
29
30
31
31
33
7. Discussion _______________________________________________________35
7.1.1 Result _________________________________________________________________________ 35
7.1.2 Method ________________________________________________________________________ 37
7.1.3 Proposals for future research ______________________________________________________ 38
8. Conclusions ______________________________________________________39
9. References _______________________________________________________40
Appendix 1: System boundaries for scenario 1, 2 and 3
Appendix 2: Inventory
Appendix 3: Differences in substance flow when certain life cycle stages are excluded
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Introduction and Objectives
1. Introduction
To decrease the disposal of waste and to save natural resources, several political initiatives
have been initiated both in Sweden and at a European level. One example is the EU Sixth
Community Environment Action Programme, which informs that natural resources
management and waste recycling are areas that should be given priority. Another example is
the Swedish Environmental Code that prescribes reuse and recycling of material. One of the
Swedish environmental quality objectives, a Good Built Environment, is also relevant for the
reuse material issue. The government has also attempted to decrease the overall volume of
disposed solid waste with a landfill tax. The overall idea of the political initiatives is that it
should be a matter of course to use alternative materials when possible and then decrease
landfilling and reduce extraction from gravel/sand pits and rock quarries. According to Arm
(2003), certain qualifications must be fulfilled before residual products can be an interesting
alternative to conventional aggregates, such as sand, gravel or crushed rock. The alternative
material must have suitable engineering properties, an acceptable environmental impact and
reasonable costs.
Approximately 1 million tonnes of ash is produced every year in Sweden.1 It has been shown
in previous studies for example by Arm (2003), RVF (2002) and Mácsik (2004), that the ash
has the technical properties to fulfil the qualifications for acting as substitute for conventional
material in ground constructions. However, it has to be proven that the ash also is
environmentally friendly before use. The environmental impacts from residuals can be
analysed with different system perspectives and according to Roth and Eklund (2003)
evaluations of residuals have so far mainly focused on measurements of total chemical
content and leaching behaviour. Roth and Eklund argue that the current leaching tests have to
be complemented by broader system boundaries in order to discuss the use of resources and
environmental impacts from a wider perspective.
2. Objectives
This thesis describes the potential for utilisation of different types of ashes in Uppsala County.
Firstly, an inventory of ash-producers and possible applications where ash can be utilised was
made. This was followed by an estimation of differences in environmental impacts that can be
expected if ash is substituting conventional material in ground constructions. The
environmental impacts are discussed in a wide perspective where both emissions and resource
use are included. The intention is to produce useful information for decision-making
concerning utilisation of ash.
The aims in more specific terms were:
•
To identify the ashes produced in Uppsala County, quantify the ash flows and give
examples of potential applications of these ashes.
• To perform an Environmental Systems Analysis (ESA) for:
- Utilisation of 1 tonne MSWI bottom ash as drainage material in the covering structure
in a landfill (substituting sand).
- Disposal of 1 tonne MSWI bottom ash.
1
Bjurström, personal communication
5
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
•
To compare these two scenarios for managing the MSWI bottom ash with the already
investigated scenario; where crushed rock in the sub-base layer of a road is
substituted by MSWI bottom ash.
Questions addressed are how the scenarios differ regarding resource use and emissions and
which processes that are significant for the difference in environmental impact. The study
takes into account the whole life cycle of the constructions (all three constructions are
assumed to be produced in all scenarios) and includes the environmental impacts generated
when ash is treated as waste and disposed of in the landfill.
3. Production of ashes
The secondary product ash is formed during the incineration process. The type of ash
produced depends on the kind of fuel and furnace used and also on what kind of flue-gas
cleaning devise that is installed in the incinerator. As stated in SGI (2003), different types of
ash have different types of environmental and engineering properties, which lead to the
varying characteristics and behaviour of different types of ash.
Normally two fractions of ash are produced from incineration, known as bottom ash and fly
ash. Bottom ash is the product that falls down and stays at the bottom of the furnace. The fly
ash travels with the flue-gases through the exhaust system and is caught in the flue-gas
cleaning system, for example an electric filter. In general, the bottom ash has been more
investigated, considering the engineering and environmental properties, probably due to the
fact that bottom ash is produced in higher amounts than the fly ash.
Arm (2003) discusses several categories of combustion systems. One is mass-burning, where
the fuel is fed directly into the furnace and burned on a gate without any pre-treatment; massburning is common for waste incineration. In other kinds of systems, a more homogenous fuel
is needed. The fuel is prepared through sieving, crushing and is generally fired in suspension
for example in a fluidised bed incinerator. Alvarez (1999) gives an example of a third system,
furnace with powder burners and as the name indicates, the fuel is in the form of powder. The
powder together with air is sprayed into the furnace, where it burns in suspension. Systems
with powder-burners produce more fly ash than mass-burning. The ashes produced in Sweden
are mainly generated from incineration of biofuels, municipal solid wastes, coal, and peat.
As previously stated, characteristics vary significantly even if they originate from the same
type of fuel. Moreover, coal ash produced in Uppsala may for example have a different
behaviour than a coal ash produced in other parts of the country. In the following sections,
short descriptions of the basic differences between ashes originating from different types of
fuels are described. Examples of how the ashes can be used are also given. Projects in
Uppsala County were considered to be the most interesting ones during the selection process
of utilisation projects due to the objectives of this study. In order to get a more complete view
of different kinds of ash utilisation, the examples were complemented with projects from
other parts of the country.
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
3.1 Coal and peat - bottom and fly ash
Chemical and physical properties
According to SGI (2003), bottom ash has a relatively large particle-size. Further, the surface
of the particles resembles glass but the inside is porous. Fly ash from coal and peat has, on the
other hand, a very small particle-size, comparable to sandy clay. These small particles consist
mainly of silica, aluminium and iron compounds. The fly ash often has a very low density and
sets easily. Peat and coal ashes have very similar technical properties and are therefore treated
as identical materials in this project.
3.1.1 Utilisation of peat and coal ash
Construction material
According to The City of Helsinki - Real Estate Department (1983) - both the bottom ash and
fly ash from coal and peat can be used in construction, for example in smaller roads where it
often substitutes crushed rock. Constructions of coal and peat ash have showed to have good
strength, a higher isolation capacity and only half of the density compared to natural rock
material. Fly ash has the advantage that it sets and becomes hard and is therefore suitable for
construction where high strength is needed. Fly ash is also useful when the construction is
exposed to a dynamic load. Unlike the fly ash, the bottom ash particles become crushed when
exposed to heavy loads, which can lead to subsidence. On the other hand, bottom ash is very
good to use in other applications, such as filling material in excavation trenches. The reason
for this is that the bottom ash never becomes hard which facilitates digging when reparation is
needed. The use of coal and peat ash in construction is not recommended when the ground
water level is high, since substances can be dissolved in water and the fly ash can also lose the
strength during contact with groundwater.
In Uppsala County, Vattenfall Värme Uppsala AB is one of the largest producers of coal and
peat ash. They also have experiences in using both fly ash and bottom ash in ground
constructions. They mix the ash with 30 % gravel and 20 % water to get a faster setting and
the construction can be used almost directly (construction with only ash extend the setting
process with 2-3 months). Problems can arise when it rains heavily, since this leads to an
extension of the setting process. The disadvantages that Vattenfall Värme has faced by using
ash are mainly logistic problems during winter, since ash can not be stored for a long period
of time. A lack of time to mix the ash with gravel occurs during the winter. This since more
ashes is produced during winter and ashes cannot be stored indefinitely without losing its
properties.2
3.1.2 Examples of projects where coal and peat ash have been used
Librobäck - recycling station, Uppsala
Librobäck is a recycling station owned by Uppsala Teknik och Service. Librobäck was built
during the winter 2001 and is constructed with a layer of fly ash originating from coal and
peat combustion. The total amount of ash used during construction was approximately 6000
tonnes. This construction benefits from the fact that fly ash only has half of the weight
compared to crushed rock. Lower weight has the benefit that the underlying clay layer doesn’t
have to be stabilised with pillars of cement, which reduces the costs. Another benefit is the
time saving, since the ash doesn’t need to set before adding the asphalt layer. A monitoring
2
Munde, personal communication
7
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
program for the station has been set up consisting of water sampling in the area, which makes
it easy to detect possible leaching. Uppsala Teknik och Service is very satisfied with the
recycling station, since it has showed good technical properties. The station is constructed
(from top to down) as follows:
Asphalt
Coal and peat
fly ash (1m)
Geofabric
Figure 1: Cross-section of Librobäck
recycling station
Figure 2: Librobäck recycling station, Uppsala
Danmark’s football field, Uppsala
A recently built ash project is Danmark’s football field just outside Uppsala. This is an
example of a combined use of bottom and fly ash from peat and coal incineration. In the
beginning of the construction, it was noted that the construction site included valuable topsoil,
which led to the decision that the soil should be sifted and sold. The consequence of this was
that even more ash was needed than estimated. The total amount of ash needed for the
construction was estimated to approximately 8000 tonnes substituting gravel and crushed
rock. Vattenfall Värme Uppsala AB will generate all the ash and they are also responsible for
the construction. The design of the construction is presented in Figure 3.3
Grass
Soil
Coal and peat fly ash (0,3 m)
Coal and peat bottom ash
Figure 3: Cross-section of Danmark’s football
field
Börje – farm roads, Uppsala
Smaller roads are the main utilisation area for coal and peat ash. One example is several farm
roads at Börje in Uppsala municipality. In total 3000 m3 fly ash generated from incineration of
coal and peat is needed to construct a 2 km long road (Larsson and Lejon, 2003). The
technical properties of roads of coal and peat ash have shown to be beneficial and have led to
that Vattenfall Värme Uppsala AB easily finds customers who are willing to use ash for farm
roads. The responsibility for the roads is always the owner, which often is a private person. So
far, the owners of ash farm roads have been very positive to the results.
Stabilization of soil with high sulphide content, Uppsala
Sulphidic soil is a sensitive soil type with low strength, easily leading to an occurring
subsidence when the soil is exposed to heavy loads. Therefore, this kind of soil often is
excavated and replaced before construction. Sulphidic soil has the problem that under aerobic
conditions, acidification and leaching of sulphides and iron may occur. Therefore, the soil
3
Munde, personal communication
8
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
should be stabilized if there is a risk that it will be in contact with oxygen.4 An experimental
work to stabilize the soil with peat bottom ash was carried out in cooperation between the
companies JM, Bjerking and Vattenfall Värme Uppsala AB. Firstly, a layer of bottom ash was
spread on the ground, covered by a layer of sulphdic soil mixed with bottom ash and finally
covered with a layer of bottom ash. A week after the application, a regular blending process
started to help oxygen to infiltrate into the pile. Due to the high pH of the ash, the pH of the
acidic soil increased. In total 200-300 tonnes of peat bottom ash were used to stabilise soil
from excavation at construction sites.5
Covering structures for the landfill Dragmossen, Älvkarleby
3 km south of Älvkarleby, the 2000 m3 landfill Dragmossen is located. According to Mácsik
(2004), Dragmossen was covered with four layers during May 2004, where two of them
consisted of fly ash (the pre-covering layer and barrier layer). The bottom layer was
constructed from fly ash generated from incineration of wood splinter and the second layer
from the bottom was a mixture of sewage sludge and peat fly ash. The two types of fly ash
used were 250 tonnes from Vattenfall Värme in Uppsala and 300 tonnes from Mälarenergi in
Västerås. The covering was performed as shown in Figure 4. Control and monitoring of the
technical properties and possible formation of gas will proceed until one year after the
covering.
Protection layer
Drainage material
50 % fly ash from Vattenfall Värme and Mälarenergi mixed with 50 % sewage sludge (0,5 m)
Fly ash from Mälarenergi (0,5 m)
Figure 4: Cross-section of the covering structures at the landfill Dragmossen
3.2 MSWI bottom and fly ash
Chemical and physical properties
According to SGI (2003), the MSWI bottom ash resembles dark greyish sandy gravel and
consists of melt or unburned material, for example glass, metals and ceramics. MSWI bottom
ash is often sorted, which means that unburned material and metals are removed. After
sorting, the ash can be sifted to desired fraction. The environmental and engineering
properties of the ashes are affected by the composition of the waste, the combustion-process
and how well the ash is sorted. The fly ash, produced from MSWI, often has an exceptionally
high content of heavy metals and is, today, considered as hazardous waste (Larsson and
Lejon, 2003). According to Arm (2003), it is recommended to store the bottom ash before
utilisation since the storage reduces the water content and the alkalinity, which improves the
environmental and mechanical properties.
3.2.1 Utilisation of MSWI ash
Construction material
Arm (2003) states that according to present Swedish regulations, MSWI bottom ash cannot be
used as construction material, unless the organic matter content is less than 2 % (measured by
colorimetric method). Nor should bottom ash from incineration of hazardous waste be used. It
4
5
Mácsik, personal communication
Munde, personal communication
9
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
is important that only bottom ash is used, since the fly ash is far more contaminated. One
example of a construction using bottom ash is roads. Bottom ash can be laid 25-35 cm below
the road surface, depending on the type and thickness of the surface layers. The same stiffness
as for natural gravel may be assumed. Construction traffic on the compacted layer should be
avoided and the bottom ash should be stored outdoors before use.
MSWI fly ash as a cement substitute
Studies by Lin et al (2003) have shown that MSWI fly ash can act as substitute for up to 20 %
of the cement in mortar, without sacrificing the quality of the resultant concrete. In fact, the
concrete thus produced has greater compressive strength, 10 % higher than the one without
the substitution. The setting time of the fresh mortar becomes longer and increases with the
increasing amounts of cement replaced.
Filling material
The MSWI fly ash is not used directly today, since it often contains very varying and high
amounts of heavy metals (Larsson and Lejon, 2003), but theoretically the fly ash could be
used as filling material, for example in old pits and limestone quarries. The problem is that
MSWI fly ash together with water can form hydrogen-gas and therefore implies a risk for
explosion. Why MSWI fly ash to some extent form hydrogen-gas is under investigation.6
Acid leaching
To get the fly ash cleaner, acid leaching could be a potential option. Acid leaching is based,
according Hernhag et al (2003), on the fact that metals dissolve when exposed to acidic
conditions. In the acid leaching process of fly ash, the ash is put into a reactor containing
process water with pH 1 and 2. The metal oxides are then forced to dissolve into the process
water and there is also an ion exchange of metals bound to the surface of the ashes main
components, Ca, Si, Al, Na and K, releasing metals into the water. After the leaching, there is
a phase separation where inert ash residue is taken away and the metals in solution are ready
to be enriched. No acid leaching exists in Sweden today. There are also other kinds of
recycling methods to reuse the metals in the ash, but they are often considered as too
expensive.
3.2.2 Examples of projects where MSWI ash have been used
Törringevägen-road, Malmö
Törringevägen, built in 1998 and owned by the municipality of Malmö, is probably the most
well-known project where MSWI ash has been used in Sweden. The road is situated 10 km
southeast of Malmö. According to RVF (2002), the road is composed of three different parts;
each part is constructed from different recycled materials in the sub-base layer. The materials
used are recycled bricks, recycled concrete and MSWI bottom ash. Between each section, a
sub-base layer consisting of crushed rock serves as a reference material. The total amount of
ash used was 320 tonnes, with a cross-section shown in Figure 5. It has been shown that the
strength of the sub-base with MSWI ash is higher then the strength of the reference material.
Asphalt
Crushed granite
MSWI bottom ash (0,465 m)
Figure 5: Cross-section of the ash part of
Törringevägen
6
Munde, personal communication
10
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
Test road at Hovgården, Uppsala
Another road described in RVF (2002), is situated within the landfill site Hovgården,
northeast of Uppsala. It is owned by the municipality of Uppsala and was built of 100 m3
MSWI bottom ash in 1996. Since the road is situated within the disposal site, it is only used
for internal transports. The bottom ash was sorted to the fraction 20-50 mm and stabilised
before use. The intended purpose of the test road was to investigate the behaviour of the ash
as road construction material and to examine any possible long-term leaching from the
material. No visible subsidence has occurred even tough the road have been daily exposed to
heavy traffic.
Area for composting, Hovgården, Uppsala
Not only a test road of MSWI bottom ash is built at Hovgården, but also a 20 000 m2 area for
composting has been constructed. The total amount of unsorted ash that was used during
construction was approximately 30 000 tonnes.7 The area is constructed as follows:
Asphalt
MSWI bottom ash 0,3 m
Gravel/Crushed rock
Figure 6: Cross-section of the compost area, Hovgården
Drainage material, Dragmossen, Älvkarleby
In the landfill Dragmossen (see section 3.1.2), not only peat ash was used for the covering
structure. Also bottom ash from incineration of wastes from the paper industry was used. The
ash was used as a drainage material during covering the landfill, see Figure 4. The ash came
from Söder Energi`s district-heating plant and had a size distribution of 0-100 mm.
Traditionally, sand is used in drainage layer in landfills. Since there weren’t enough bottom
ash for coving the whole landfill, also sand was used in some parts of the drainage course at
Dragmossen.8
SYSAV, combined heat and power plant, Malmö
It is stated in RVF (2002) that during construction of SYSAV`s new waste incineration plant,
in the years 2000-2002, MSWI bottom ash was used in several different applications. For
example, the ash was used in ground constructions where the soil was weak and polluted.
Further more, ash was used as filling material in excavation trenches and as a material against
walls. 14700 m3 bottom ash was used in total, substituting crushed rock. Today when
SYSAV`s new plant produces MSWI ash, all generated bottom ash is used in different
constructions. According to Kärrman et al (2004) in total six external projects have been
performed and 10000 tonnes of ashes have been used in each project. Examples of projects
are recycling stations in Malmö and the road Törringevägen.
3.3 Biofuel - bottom and fly ash
Biofuel is often defined as biomass. Biomass is mainly composed of carbon, hydrogen and
oxygen and has been created by metabolic activity of living organisms. In this report, the
expression biofuel refers to wood material, for example bark, recycled wood waste, Salix etc.
7
8
Kjällman, personal communication
Mácsik, personal communication
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Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
As discussed in Ek and Westling (2003), the content and structure of the ash resulting from
incineration of biofuel depends on the type of furnace and on kind of biofuel used. Biofuel has
a significantly varying quality and characteristics due to the fact that soil conditions differ.
For example, different fertilisers are used in different areas giving the biofuels specific
characteristics. The most notable difference between the fly and the bottom ash is the particle
size. The fly ash has a smaller particle size and a higher content of lead, cadmium, and zinc.
3.3.1 Utilisation of biofuel ash
Ash recycling
As declared in Ek and Sundqvist (1998), biofuel ash is nutrient-rich, which can counteract
unwanted changes of the soil in the forest, and therefore the majority of biofuel ash producers,
are involved in some manner of different projects where the ash is spread on forestland. The
main purpose is to return nutrients to the soil in an effort to compensate the withdrawal of
biofuel, leaching and acidification. For the ash to be suitable for spreading, it has to fulfil
specific criteria, such as having a low metal content and it has to originate from biofuel.
Factors that have to be considered before using ash as a fertiliser are:
• The ash has to be stabilised and dry, but not dusty.
• The leaching of nutrients has to be slow.
• The ash should not contain a high amount of heavy metals and organic compounds.
According to the National Board of Forestry, ash intended for use as a fertiliser to counteract
withdrawal, can only be used on the following soil types:
• Strongly acidic soil.
• Peat.
• Where a large withdrawal of branches has occurred.
• Where there have been several withdrawals.
The biofuel ash effectively sets and together with water forms a material with low
permeability. This material can be crushed and sifted to appropriate size to give the right
leaching properties (Ek and Westling, 2003).
Construction material
According to Ek and Westling (2003), mainly the biofuel bottom ash should be considered in
construction, because fly ash does not have satisfactory strength. A problem with the bottom
ash is the high variability and relatively high content of unburned material, which can lead to
subsidence. Therefore only smaller roads, such as farm roads are built of biofuel ash today.
Another example of construction where the bottom ash has started to be more frequently used
is in excavation trenches for water and waste pipes, where in the past traditional crushed rock
or natural gravel were used (Eriksson, 2001).
Method from Econova
The Econova method (Figure 7) is according to Ek and Westling (2003) based on drying the
fly ash originating from biofuel and then using it for soil improvement or for incineration. The
drying process is natural, consisting of wind and sun only, by placing the ash on a flat
foundation. As soon as the surface is dry the material is turned, usually with the result that the
ash is totally dry within a year and can then be used.
12
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Production of ashes
Figure 7: Stages applied in the Econova method
Source: www.econova.se
Ash as a landfill covering material
In Sundberg et al (2003), it is described how stabilised sludge from wastewater treatment
plants mixed with ash from incineration of biofuel, gives a product that can be used as landfill
covering material. When the materials are added together, beneficial properties of both
materials can be utilised, such as the low permeability of the sludge and the high strength and
gasket properties of the ash.
3.3.2 Examples of projects where biofuel-ash has been used
Landfill covering, Kristianstad
Sundberg et al (2003) also gives an example from the municipality of Kristianstad, where they
have been working with a mix of ash, sludge, and gravel as a covering material at a landfill,
since the year 2000. Several different mixes have been tested and today the mix consists of 50
% sludge, 25 % ash (both fly and bottom ash) and 25 % gravel. After mixing, the material has
to be stored for 4-6 weeks to get a good consistency easy to work with. The mix is flattened
out on the landfill and the final thickness of the cover is 0,8-1 m. Earlier, when a higher
percentage of ash in the mix was tested, there was a problem with smell of ammonia. Another
problem was leakage of nutrients, especially during wintertime, since the vegetation on the
landfill could not assimilate the nutrients.
Spreading of ash on Salix cultivation, Enköping
Salix is an energy crop and is only cultivated with the purpose to act as fuel, in, for example,
district-heating plants. ENA Kraft in Enköping uses a mix of 15 % Salix and 85 % wood
splint for incineration and the bottom ash produced is stored during the wintertime and is
mixed later with sludge from the municipal wastewater treatment plant. During the spring, the
mix is spread on the Salix-cultivation with a traditional fertilizer spreader (Figure 8). This is
an experiment for a period of ten years. The farmers have so far been very positive to the
experiment.9
9
Johansson, personal communication
13
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Environmental Systems Analysis
Figure 8: Ash recycling in Enköping
Source: Eklund, personal communication
Farm roads, ash from Hylte Bruk
Ek and Sundqvist (1998) have described how bottom ash originating from bark incineration at
Hylte Bruk, has been used in smaller roads, with a length of only 3-4 km. The road core is 70
cm, which implies that 3-4 tonnes of ash was needed per meter of road. A layer of gravel was
placed on top of the ash and the slopes were covered with sludge. An evaluation of the project
showed that the road had slightly less strength than roads of conventional material, especially
for the slopes. Restrictions concerning the proximity of the ash constructions to watercourses
and the groundwater level, led to addition of an extra layer in order to fulfil the construction
restrictions.
3.4 Examples of the use of fly ash independent of origin
Granulated cement stabilised fly ash
To granulate ash, means that the fine ash particles bind together during rotation in a drum,
forming larger particles. According to Larsson and Lejon (2003), this can be performed by
wet ash powder moving in a loop in a rotating plate or drum, during transport allowing the
particles to pick up the fine material and grow bigger. Cement stabilised means that the
granulated ash is mixed with cement and water. The resulting product can be used in several
areas, for example in road construction, as drainage material, fertiliser, soil stabilisation, and
as barrier material. The granulate ash should be used in an as dry environment as possible to
minimise leaching.
4. Environmental Systems Analysis (ESA)
Social awareness concerning protection of the environment and possible effects on the
environment from the products used today has increased in the last years. This has led to an
interest in developing methods to understand and reduce the impact on the environment.
Moberg et al (1999) describe different kinds of Environmental Systems Analysis (ESA). The
one that will be used in this thesis will show the environmental impact from a system in a
holistic view, including all subsystems and their interrelations. An ESA can be one way to
14
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Environmental Systems Analysis
help a decision-maker with a problem of complex character. The purpose is to contribute to a
good decision-making, by investigating the different alternatives and comparing the
consequences of each alternative.
Utilisation of ash will lead to both positive effects like less disposal of ash and negative
effects like risk for contaminant leaching. To get a view of what types of environmental
impacts that is of high importance an ESA can be useful. An ESA approach will also give the
opportunity to discuss the differences of environmental impact between utilisation of ash and
disposal of ash. The ESA-method will thus be a helpful tool to give the study a wide
perspective.
One well-known example of ESA is a life cycle assessment (LCA), which consists of, 1)
definition of problem, 2) inventory, 3) impact assessment, 4) analysis of the result (Rydh et al,
2002).
Definition of the problem
This part should include a description of why the LCA is being performed and what the result
is going to be used for. For comparisons of different systems, a common denominator is
needed. In a LCA, the denominator is the functional unit, which has to be measurable. The
environmental impact must be related to this unit for each alternative in order to make the
comparison stringent. It is not only the functional unit that has to be decided at this moment,
also the technical, time and geographical system boundaries have to be formulated in detail.
The system boundaries are important because they describe the limits of the study.
Inventory
According to Rydh et al (2002), the inventory process contains the data collection and
calculation of material and energy flows in and out from the systems. The result of the
inventory is the sum of all in - and outflows related to the functional unit. The increasing
amount of information concerning the system acquired during the data collection, can lead to
new demands and maybe new limitations have to be defined. This can lead to a change of
direction during the process of data collection in order to fulfil the aim of the study (ISO
14040:1997).
Impact assessment
Rydh et al (2002) describes that an environmental impact assessment in an LCA should be
made to evaluate the major effects on the environment. The purpose is to transform the data
from the inventory to a few values that are easy to interpret. The assessment can be divided
into three steps; classification, characterisation and valuation.
•
•
•
Classification, the data is sorted in different environmental impact categories; examples of
these kinds of categories are eutrophication, green house effect and acidification.
Characterisation, the data from the inventory is multiplied with a characterisation factor,
which is specific for each data and category of environmental impact. The aim of the
characterisation is to quantify the mutual relationship between the different forms of
environmental impact that has been grouped in the respective environmental impact
category.
Valuation, consists of ranking, weighting and finally adding the result from the inventory
to only one number. There are several weighting methods, which are based on individual
or political and/or moral valuations. Examples of valuation methods are; Environmental
15
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Environmental Systems Analysis
priority in product development (EPS), ECO-indicator 95, Tellus, Critical volume, Critica
Surface-Time and Energy Consumption Reduction (Peterson, 2004).
Analysis of the result
The result from the inventory and the result from the environmental impact assessment are at
this stage combined in consensus with the aim of the study. Questions about what are large
and small environmental problems respectively have to be answered for all alternatives. This
will display how the different alternatives can be optimised from an environmental point of
view. The result of the analysis can take the form of conclusions and recommendations to
decision-makers (ISO 14040:1997).
There are different types of analysis that can be used. Below is a short description of three of
them (Strand, 2003).
•
•
•
Dominance analysis – identifies the data that is contributing relatively most to the result.
Uncertainty analysis – describes the variance in the amount of data. It is made to quantify
the uncertainties in the three phases: Definition of the problem, inventory and impact
assessment.
Sensitivity analysis – measures how changes can affect the result.
4.1 Previous studies in the area of ESA for waste management
There are some examples where ESA has been used for evaluation of ash utilisation in road
constructions and other types of ground constructions. A progressing research by Olsson et al
(2004) at the Royal Institute of Technology in Stockholm, has the aim to describe the
differences in environmental impact that can be expected if crushed rock in the sub-base of a
road, in the Stockholm region, is substituted by MSWI bottom ash. It has been shown that the
ESA approach allows both resource use and emissions to be considered and therefore gives a
different result then a more narrow study. A master thesis has also been done within the area.
Here the aim was to compare and estimate the environmental load from different lightweight
materials in road construction with an ESA approach (Peterson, 2004). In Finland, there is a
successful example from Mroueh et al (2001), where the ESA-approach was used for
comparison and evaluation of alternative road and earth constructions. An Excel-based life
cycle inventory analysis was developed.
Also for other parts of the waste management system, the LCA approach has shown to be a
useful tool for assessing environmental impacts. One example is from Sonesson et al (1997),
where the model ORWARE (Organic Waste Research) was used to illustrate the
consequences of different waste handling systems in Uppsala. The result showed that the
model was versatile and that it produced useful information about complex systems, but at the
same time a number of general problems with this type of analysis became apparent. The
most important of these problems are; lack of reliable input data, difficulties in defining and
applying appropriate system boundaries, selection of appropriate scenarios and evaluation
problems.
16
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
5. Method
5.1 Part 1 - Inventory of ashes in Uppsala County
5.1.1 Ashes in Uppsala County and their potential use
Part 1 of this thesis will give a view of the different types of ashes produced in Uppsala
County. The ashes included in the investigation were those produced in quantities of more
than 1000 tonnes/year and plant. This amount can be considered as the critical level for
utilisation for example in different types of ground constructions.
Information about the companies and plants in the area, that produce large quantities of ash,
was received from the County Administrative Board. More detailed information was found in
the environmental reports from each plant. Interviews were also performed to get more
complete information.
5.1.2 Selection of ash
The result from section 5.1.1 shows what types of ashes that are produced in Uppsala County.
The question now is which type of ashes should be investigated further in the ESA? To solve
this problem four selection criteria were formulated:
•
•
•
•
Produced amount of ash.
Expected environmental impact.
Documented applications.
Data availability.
The reason for inclusion of the first and second criteria is that a higher amount of ash gives a
greater opportunity for utilisation. If the ash is also expected to have a high environmental
impact, it can be seen as a “worst-case scenario” compared to the other ashes. The criterion
documented applications means, that it should be proven by existing examples of utilisation,
that the ash has the technical properties needed for the utilisation purpose. Finally data
availability is also important to make the ESA reliable.
Considering the selection criteria, the following arguments contributed the most to the final
decision:
-
The MSWI bottom ash, the coal and peat fly ash are produced in large amounts.
The MSWI bottom and fly ash are expected to give a relatively high environmental
impact due to the content of heavy metals.
The ashes that have the most documented applications, together with high data
availability, are the fly ash from coal and peat and the MSWI bottom ash. The MSWI
fly ash does not have any documented utilisation areas, since it is considered as a
hazardous waste.
The MSWI bottom ash and the coal and peat fly ash were chosen to be the investigation
objects for the two case studies in the project by Värmeforsk Q 248 (see preface). Of these
two ashes the MSWI bottom ash was selected to be the investigation object for this thesis.
17
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
5.1.3 Selection of utilisation scenarios
A requirement of the selected utilisation scenarios were that they should be viable in a
technical view and therefore the utilisation areas exemplified in section 3.2, are given priority.
Three potential scenarios were studied for the MSWI bottom ash as theoretical cases, but they
are based on experiences from real projects. The three scenarios were as follows:
1. MSWI bottom ash used as drainage material in a covering structure in a landfill.
Source of information: the landfill Dragmossen, Älvkarleby.
2. MSWI bottom ash used as sub-base material in road construction.
Source of information: the road Törringevägen, Malmö.
3. Disposal of MSWI bottom ash.
Source of information: the landfills Dragmossen, Älvkarleby and Hovgården, Uppsala.
Scenario 2 is already done in a progressing-reach study from Olsson (2004) and was included
in the thesis for a comparison purpose. At the landfill Dragmossen, the drainage layer was
made of bottom ash originating from incineration of waste from the paper industry. However,
the construction of the drainage layer was performed in the same way as if the ashes
originated from incineration of municipal solid waste. The case of Dragmossen was therefore
used as an information source.10
To understand the scenarios, a basic knowledge of landfill structures is needed. A short
description of the different layers in a landfill covering structure and their function follows
below.
Landfill structures
According to Mäkelä and Höynälä (2000), the cover of a landfill is divided into the following
structures (from the top):
•
•
•
•
•
Vegetation layer – Servers as a substratum on top of the landfill cover in which plants
and trees are planted. Furthermore, the structure protects lower layers from erosion.
Surface layer - Protects lower structure layers from the roots of the upper plants and
trees and from other mechanical loads. In addition, the layer slows down the
penetration of rain and thawing waters into the lower drainage layer.
Drainage layer - The drainage layer is the part of the landfill that directs upper rain
and thawing waters into the collecting ditches outside the landfill area. The
requirements for the drainage layer are: sufficient water permeability and frost
resistance.
Barrier layer - The barrier layer prevents the entrance of upper seepage water to the
lower structures and the waste itself. Besides, the barrier layer must stop the waste
gases so that the gases do not escape into air. The functionality and durability of the
structure are particularly important so that the whole landfill structure serves as
designed.
Pre-covering layer - With the pre-covering layer, the surface of the waste material is
shaped and levelled down so that the upper layers can be built in a relevant way.
In the section below, a more specific description of the studied scenarios is given.
10
Tham, personal communication
18
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
5.1.4 Description of the chosen scenarios
Scenario 1
In scenario 1, the MSWI bottom ash is used as a drainage material in a covering structure in a
landfill. The studied drainage layer of the MSWI bottom ash is 0,1 m thick. Geofabric is
placed both on the top and on the bottom of the drainage layer. The function of the geofabric
is to hold the drainage material in the right position. The geofabric also facilitates recycling
of the material during a future demolition of the landfill. The dimensions of the drainage layer
can be seen in Figure 9.
Geofabric 0,0018 m
MSWI bottom ash 0,1 m
Geofabric 0,0018 m
Figure 9: Cross-section of drainage layer of MSWI
bottom ash. Included in scenario 1.
In this scenario, the sub-base layer in the road will be built of the conventional material
crushed rock and there is no landfill of MSWI bottom ash (Table 1). For dimensions of the
base-course and sub-base layer in the road, see Figure 10.
Table 1: The inflows of material in scenario 1
Drainage layer
MSWI bottom
ash
Road
Crushed rock
Landfill
-
Base-course
Crushed granite
0,08m
Sub-base
Crushed granite
0,465
Figure 10: Cross-section of the road.
Scenario 2
In scenario 2, the MSWI bottom ash is used as a sub-base material in road construction. Since
the presence of the MSWI bottom ash in the sub-base layer requires a somewhat thicker basecourse layer, both these layers have been included in the study. Information considering the
dimensions can be seen in Figure 11.
19
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
Base-course
Crushed granite
0,15 m
Sub-base
Bottom ash
0,465 m
Figure 11: Cross-section of road with a
sub-base layer of bottom ash
A traditional drainage layer in a covering structure is made of sand. The only difference
between the traditional drainage layer of sand and the drainage layer of MSWI bottom ash are
that geofabric is not needed (Figure 12). There is no landfill of ash in this scenario (Table 2).
0,1 m sand
Figure 12: Cross-section of drainage layer of conventional
material, sand. Included in scenarios 2 and 3.
Table 2: The inflows of material in scenario 2
Drainage layer
Sand
Road
MSWI bottom
ash
Landfill
-
Scenario 3
Scenario 3 implies disposal of the MSWI bottom ash. The dimensions and different material
in the landfill structures have been discussed with people working in the sector, to get an as
realistic scenario as possible. The chosen structure can be seen in Figure 13.
1) Vegetation layer, topsoil, 1,35 m
2) Surface layer, excavated soil, 0,5 m
3) Drainage layer, sand, 0,1 m
4) Barrier layer, geosynthetic clay liner, 0,1 m
5) Pre-covering layer, sand, 0,2 m
Figure 13: Covering structures for the theoretical
landfill case (included in scenario 3)
This scenario includes that the road and the drainage layer is built of conventional material
(Table 3). For dimensions of the drainage layer see Figure 12 and for the road see Figure 10.
Table 3: The inflows of material in scenario 3
Drainage layer
Sand
Road
Crushed rock
Landfill
MSWI bottom
ash
20
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
5.2 Part 2 - ESA for different possible uses of MSWI bottom ash
The method used in this part of the study is an Environmental Systems Analysis (ESA), based
on the concepts of life cycle analysis (LCA). The method is under development in a
progressing research at the Royal Institute of Technology, by Olsson et al (2004) and in the
project by Värmeforsk Q 248 (which this thesis is a part of). In the research by Olsson et al
(2004), the method has been used for utilisation of MSWI bottom ash in the sub-base layer
during road construction. This thesis will contribute with an expandsion of scenarios of
utilisation areas for MSWI bottom ash within the method and an improvement of data quality.
In the next section, a short general description of the method follows.
5.2.1 General description of the method - ESA for the use of residuals in a regional
perspective
First the scope of the study and the system boundaries are defined. The system boundaries
should include all significant stages of the product’s life cycle. The system should also
include disposal of the studied material if this is a realistic alternative. This enables evaluation
of how the utilisation of the residuals may impact the overall environmental performance of
the system. By including disposal, the effects of less landfilling can be considered. Different
products that are used in the system for example fuel and machineries, are included to a
limited extent, see Figure 14 for a view over products and the stages of their life cycles that
are taken into account in the ESA.
Fuel
Electricity
Raw
material
System
boundaries
Products
Emissions to air
Emissions to water
Rawmatrial
Figure 14: Life cycle steps for the products that are included in the study.
Source: Olsson et al (2004)
In the next stage, the functional unit is to be decided and defined. The functional unit should
consist of utilisation of a certain amount of residuals in a certain region. The functional unit
should also include the products and functions that the residuals can be used for. The
following step in the method is an inventory; this is where the emissions from the system are
quantified. Only the flow of resources or emissions that have potential to affect the
environmental impact categories in the forms that are described by SETAC-Europe (1999) are
taken under consideration. Other criteria for the choice of environmental flows are that there
should be available data to enable quantification and that the flows should be significant for
the study. The data collection should be based on experiences from real projects. It is also
good if the data is representative for the region and is as up-to-date as possible. Factors that
are specific for the region, for example distance for transport should undergo a sensitivity
analysis. Finally, the result is analysed. The result will address how the alternatives differ
21
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
regarding resource use and emissions. The following sections describe how the method has
been applied in this thesis.
5.2.2 System boundaries and functional unit
The system includes production of material, construction and use and maintenance of the
construction for 100 years. The production of MSWI bottom ash and possible demolition
phases are not included in the system, depending on lack of data. A sketch of the system is
given in Figure 15.
Resources and MSWI bottom ash
Production
of material
to
and account during the study
of sub-base
Sketch
over system
boundaries
and Production
life cycle stages
taken into
drainage layer
base-course material
Waste
Disposal
Construction of drainage
layer
Construction of sub-base
and base-course layers
Use and maintenance of
drainage layer for 100
years
Use and maintenance of
the road for 100 years
Emissions
Figure 15: Sketch over system boundaries and life cycle stages taken into account during the study
MSWI bottom ash and resources are flows that enter the system, outflows from the system are
emissions. The system also includes disposal of MSWI bottom ash as a life cycle stage. The
system also implies that the different scenarios will always be performed; this means that the
system is producing three services. Firstly the drainage layer in a landfill, secondly the subbase and the base-course layers of a road and finally the disposal of certain amount of MSWI
bottom ash. Since the presence of MSWI bottom ash in the sub-base layer requires a
somewhat thicker base-course layer, both these layers have been included.
The MSWI bottom ash will in each case substitute the conventional material. A drainage layer
in a landfill is traditionally made of sand. In sub-base and base-course layers in roads the ash
substitutes crushed granite. This implies that the scenarios have different inflows of material
see Appendix 1 for more detailed information.
Scenario 3 is in some way different compared to the other scenarios. For example this
scenario includes production of many different materials since all this material is needed for
the covering structure in a landfill. See Figure 16 for a description of the life cycle stages
taken into account in scenario 3.
22
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
Resources and the MSWI bottom ash
Production of the material needed for
the landfill structure: soil, sand, and
geosynthetic clay liner.
Construction of the landfill structure:
vegetation layer, surface layer, drainage
layer, barrier layer and pre-covering
layer
Use and maintenance of the landfill for
100 years. Includes the leachate from
each covering layer and the leachate
from the MSWI bottom ash disposed in
the landfill.
Emissions
Figure 16: Life cycle stages taken into account for scenario 3
As the method prescribes, the functional unit should consist of both utilisation of a certain
amount of residues and the products/functions that the residues can be used for. According to
this the following functional units were chosen:
- Utilisation of 1 tonne MSWI bottom ash.
- Production of 0,5714 m3 drainage layer in the landfill.
- Production of 0,1536 m road.
5.2.3 Inventory
The criteria for the choice of flows were that there should be data available to enable
quantification and that the flows should be significant for the study. Based on this, the
following environmental flows were included: natural aggregates and energy and emissions to
air and water. One example, where not enough data was available, was the uses of human
resources and occupation the of land area. Therefore these parameters have not been
considered in the study. Only those life cycle stages that were different from scenario to
scenario were included in the analysis; similar parts of the system thus were excluded.
As mentioned earlier, the data for the scenario to use the MSWI bottom ash in the sub-base
layer during road construction has been obtained from Olsson et al (2004). Data for the
remaining scenarios was obtained from literature and interviews with people working in the
sector. It was intended to assemble the data that was representative for Uppsala County and as
currently valid as possible. A more specific description of the data collection and assumption
made for the study is given in the following sections, and the whole inventory with references
can be found in Appendix 2.
23
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
Parameters for the MSWI bottom ash
All parameters connected to the engineering properties of the MSWI bottom ash, for example
density, were obtained from Vattenfall Värme Uppsala AB.
Production of drainage material from the MSWI bottom ash
The distribution of the ash from the plant to the sifting area is not taken into account, since the
ash always will be transported to a sifting/storing area before utilisation.11 This transport can
be seen as a part of the production of the MSWI bottom ash, and is therefore not included in
the life cycle stage production of the drainage material. To produce drainage material from
MSWI bottom ash, the ash has to be sifted to remove metals and organic compounds. To get
information about the sifting procedure, interviews where performed with the company Slag
Recycling AB. During the inventory it became clear that the sifting procedure could be
excluded from the analysis, since the MSWI bottom ash will be sifted in all scenarios (even if
the ash will be disposed of). 12 After sifting, 80 % of the ash remains, which means that the
life cycle stages construction and use and maintenance of the drainage layer have a 20 %
lower inflow of the MSWI bottom ash, than the life cycle stage production of drainage
material (RVF, 2002). The geofabric used in the study was produced by Naue Fasertechnik in
Luebbecke, Germany, and transports of the geofabric were calculated to be from here.
Emissions factors for production of geofabric were taken from Svingby and Båtelsson (1999).
Production of drainage material from sand
The production of the drainage material from sand includes the extraction of sand and the
loading of sand to truck. The data for the inflows to this life cycle stage were obtained in
interviews with the company Jenaders Grus, who has the experience in delivering sand for the
purpose to be used as drainage material in landfills. According to Jenaders Grus, a loading
machine of the type Volvo L180 E is used for extraction and loading of sand and therefore
figures for this machine were used.
Construction of drainage layer (of both sand and MSWI bottom ash)
At the source of information, Dragmossen in Älvkarleby, some parts of the drainage layer are
constructed with sand and some parts constructed with bottom ash. The machine used for the
construction of the layer was an excavator of the type Volvo EC240 for both materials.
During interviews with people producing excavators, it was discovered that an excavator has
a big difference in energy consumption depending on if the scoop is filled or not. Based on
the experience from Dragmossen, the excavator was assumed to be working with a filled
scoop 50 % of the time and with an empty scoop 50 % of the time. The geofabric used in
scenario 1 is manually put on the MSWI bottom ash. The drainage layer cannot be driven on
and is therefore not compacted; therefore the density for non-compacted MSWI bottom ash
has been used in all calculations for the drainage layer.13
Use and maintenance of the drainage layer (of both sand and MSWI bottom ash)
Data about the leachate from the MSWI bottom ash was obtained from the The Swedish
Association of Waste Management (RVF, 2002). The leaching data for sand was found in the
studies from Mroueh et al (2001) and Gustafsson et al (2003). The amount of leachate is
dependent on how much water the material is in contact with. A drainage layer is supposed to
direct rain coming from above and based on this the calculations have been made on the
11
Ericsson, personal communication
Reference group, personal communication
13
Mácsik, personal communication
12
24
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
assumption that all infiltrated water (200 mm) will reach the drainage layer. To get a view of
how the contamination have varies over time, the leachate from both materials were
calculated for time perspectives of 50, 100 years and infinity. The leaching approximations
are based on different tests, for different time perspectives. For the infinity perspective, data
from the standardized availability test Nordtest NT ENVIR 003 have been used. For the two
shorter time perspectives, data from batch leaching tests was used. The batch leaching tests
were done according to the CEN-method. This means that the leaching at the liquid-solid
(L/S)-ratio of 2 or 10 may be approximated as being equivalent to the leaching from the
different scenarios during a 100-year period. The ratio that has been used depends on the time
it takes to reach L/S 2 or L/S 10, see Table 4. The ratio closest to 100 years has been used.
This lead to for example that leaching from scenario 2 is obtained by a liquid-solid ratio of 2
for both the ash and the crushed rock and leaching data for the drainage layer of MSWI
bottom ash is estimated from CEN tests using a liquid-solid ratio of 10 (Table 4). The
geosynthetic clay liner and the geofabric have a lifetime of more than 100 years.14 It has
therefore been assumed that no leaching from the geofabric and the geosynthetic clay liner
during 100 years occurs.
Table 4: Time to reach L/S 2 respective L/S 10
Time to reach L/S 2 for MSWI BA in drainage layer (scenario 1)
1,4 years
Time to reach L/S 10 for MSWI BA in drainage layer (scenario 1)
6,9 years
Time to reach L/S 2 for sub base with MSWI BA (scenario 2)
99,2 years
Time to reach L/S 10 for sub-base with MSWI BA (scenario 2)
496 years
Time to reach L/S 2 for base course with crushed rock, (scenario 2)
40 years
Time to reach L/S 10 base course with crushed rock, (scenario 2)
200 years
Time to reach L/S 2 for crushed rock road (scenario 1 and 3)
145 years
Time to reach L/S 10 for crushed rock road (scenario 1 and 3)
727 years
Time to reach L/S 2 drainage layer of sand (scenario 2 and 3)
1,6 years
Time to reach L/S 10 for drainage layer of sand (scenario 2 and 3)
7,9 years
Time to reach L/S 2 for pre-covering layer of sand (scenario 3)
Time to reach L/S 10 pre-covering layer of sand (scenario 3)
12,8 years
64 years
Time to reach L/S 2 for MSWI BA disposed in a landfill (scenario 3)
960 years
Disposal of MSWI bottom ash
The leachate from the landfill has been assumed to go through a water treatment plant the first
20 years. This means that chemicals needed for the treatment was included in the analysis, but
neglecting that a landfill contains more residuals than MSWI bottom ash. Since this scenario
includes many parameters, each layer is described below to give a clear view.
Vegetation layer: The calculations are based on the assumptions that an excavator does the
excavation of soil and the soil is loaded directly to a lorry. The distance from the excavation
site to landfill has been assumed to be 20 km. The leachate from the soil layer in the landfill
will be the same in natural conditions; therefore no leaching is taken into account.
14
Burton and Sjöholm, personal communication
25
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
Surface layer: By discussions with people in the landfill sector, it became clear that the soil
used in the surface layer often is soil that already exists in the landfill area. The soil comes
from excavation during different ground-constructions, and is considered as waste.15
Therefore the soil is only considered as a direct inflow to this life cycle stage. However, the
soil used in the surface layer cannot be contaminated; it means that the leaching from the soil
is assumed to be the same as in natural conditions. Therefore no leaching from this layer has
been assumed. An excavator makes the construction.
Drainage layer: All calculations and assumptions are the same as for the drainage layer of
sand (see above).
Barrier layer: The geosynthetic clay liner in the barrier layer is produced by Naue
Fasertechnic in Luebbecke16, Germany, and the transports are assumed to be from there. It
was very hard to find information about resource use during production of the geosynthetic
clay liner. However, since the information about the geofabric was relatively good the
geosynthetic clay liner in this study was simplified to consist of a bentonite layer with
geofabric on top and at the bottom. According to Gävle Väg trummor AB the geosynthetic
clay liner consist of 95 % bentonite and 5 % geofabric. Bentonite is extracted through strip
mining, where core drilling machines, dozers and front-end loaders are used17, but reliable
information about working capacity and fuel consumptions for machines were not found. It
was decided to do two calculations one where the barrier layer is excluded from the analysis,
and one were values from an LCA of mining of magnetite ore is substituting the life cycle
stage production of material for the barrier layer.
Pre-covering layer: Sand is used in the pre-covering layer, therefore the same parameters and
assumptions are used as for the drainage-layer of sand. The only differences are the
dimensions and the infiltration rate. According to Swedish regulations, the maximum water
going through a landfill is 50 l/m2 year and this amount of water has been assumed to reach
the pre-covering layer.
Transports
According to Jehanders Grus, sand is distributed by the aid of a lorry with a trailer. This lorry
could take a maximum load of 35 tonnes. To facilitate the study, it was assumed that the same
kind of lorry and trailer were used for all transports; distribution of MSWI bottom ash, soil,
geofabric, and geosynthetic clay liner. The calculations were also made with the assumption
that the lorry had maximum load during distribution and returned empty. It should be noted
that spillage of material during transport has not been taken into account. The average
velocity during transport was assumed to be:
Table 5: Assumed velocity
Distance
Less than 7 km
7 – 20 km
More than 20 km
Assumed velocity
50 km/h
70 km/h
90 km/h
According to the County Administrative Board in Uppsala (2004) there are two landfills that
will be closed before 2008, Annelund in Enköping, and Gatmots in Tierp. This means that
these two need drainage material for their landfill structure. The average distance from
Uppsala to these landfills is 55 km. This distance has been assumed for transport of MSWI
15
Laurell, personal communication
www.naue.com
17
Burton, personal communication
16
26
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Method
bottom ash from production site to construction site. If these two landfills will build theirs
drainage layer of sand instead, the most reasonable solution would be to take sand from the
closest sand pits. The landfills Annelund and Gatmots have a distance of 5 respectively 8 km
to the nearest sandpits (SGU, 2003).
Electricity
The emission factors for electricity are taken from Stripple (2001). These values only
represent the production of electricity; no impacts from extraction of raw materials and
transport are included in these values.
Fuel consumption
For the use of fuel, pre-combustion values for fuel production have been included according
to Stripple (2001).
Machine use
Estimations of the lifetime of the different machineries have been made together with people
that produce the machineries included in the study. During the lifetime the machines have
been assumed to be working eight hours per day and five days per week. All the machines are
made of steel.
5.2.4 Analysis of the result and Impact Assessment
The Swedish parliament has established 15 environmental quality objectives to guide Sweden
towards a sustainable society. The Swedish Environment Protection Agency defines the 15
objectives as follows; they will function as benchmarks for all environment-related
development in Sweden, regardless of where they are implemented and by whom and the
overriding aim are to solve all major environmental problems within a generation.18 To get a
view of the kind of resulting effects from the different flows from the system, each flow was
connected by the environmental objectives that are influenced the flow.
As mentioned above, all parts of the system that were similar in all scenarios were excluded
from the study. This means that the result does not show the total environmental impact
caused by each case. It shows the specific environmental flows that occur from each scenario.
To enable comparisons between the scenarios, data on all flows were normalized by division
with the national flow of each kind per person in Sweden. These values can be seen as an
indication of what is large and small. The flows that are of greater significance than others
were discussed more deeply and the assumptions made for calculation of these flows were
more specified.
6. Result
6.1 Result part 1 - Inventory of ashes in Uppsala County
The inventory showed that two district-heating plants and two combined heat and power
plants produce more than 1000 tonnes/year (fly ash and bottom ash are added together). The
specific amounts of ash are shown in Table 6.
18
www.naturvardsverket.se
27
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
Table 6: Ash production in Uppsala County
Producer and location
Type of fuel and type of furnace
Fly ash
[tonnes/year]
and water
content
Bottom ash
[tonnes/year]
and water
content
Vattenfall Värme Uppsala AB
District-heating plant
Vattenfall Värme Uppsala AB
Combined heat and power plant
Municipal and industrial solid waste
Mass-burn-type with moving grates
Coal and peat powder
Solid fuel furnace with powder
burners
Biofuel: wood splinter and bark
Mass-burn-type with moving grates
5749,
36 % H2O
26 838,
20 % H2O
37 830,
20 % H2O 1
9616,
55 % H2O 1
485, 46% H2O
728 , 46 % H2O 2
Biofuel: wood splinter (85 %) and
energy crop; Salix (15 %)
Mass-burn-type with moving grates
and solid fuel boiler with powder
burners
915, 50 % H2O 1410,
25 % H2O 3
Vattenfall AB Värme Norden Små
och Medelstora Anläggningar,
Knivsta. District-heating plant
ENA Kraft AB, Enköping
District-heating plant
1) Miljörapport Uppsala, Vattenfall Värme Uppsala AB 2003
and Ericsson, personal communication.
2) Miljörapport Knivstaverket, Vattenfall AB Värme Norden Små och Medelstora Anläggningar 2003 and
Strömbäck, personal communication.
3) Eklund and Johansson, personal communication.
Vattenfall Värme´s combined heat and power plant uses peat powder more than coal as fuel,
but the ash from both has been added because characteristics are similar. It should also be
noted that there is only production of ash from the municipal solid waste incineration and fly
ash from Enköping during the summer.
Vattenfall Värme Uppsala AB is currently in the middle of a construction expansion, which is
scheduled for completion in February 2005. This expansion will add a new furnace for
incineration of municipal solid waste, which will increase their amount of bottom ash to
56580 tonnes/year and the amount of fly ash to 9500 tonnes/year.19
The district-heating plant in Knivsta is constructed to give only one ash fraction after
incineration; in this fraction the fly ash and the bottom ash are mixed. It is therefore difficult
to estimate the percentage of the fly respectively bottom ash. In this case the estimation has
been 40 % fly ash and 60 % bottom ash of a total yearly production of 1212 tonnes.20 This is
also the reason why the fly ash and the bottom ash have the same water content.
The remaining ash that is produced in the County, comes mainly from small district-heating
plants, one exception is the fifth top producer of ash in the area, the paper mill Skutskärs bruk,
which has a yearly production of 960 tonnes.21
19
Ericson, personal communication
Strömbäck, personal communication
21
Bjurström, personal communication
20
28
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
6.2 Result part 2 - ESA for different possible uses of MSWI bottom ash
6.2.1 Environmental flows connected to the 15 environmental quality objectives
The different flows from the system have all different impacts on the environment. Emissions
of metals may cause ecological toxicity. Further, emissions of CO2 may cause climate change,
emissions of SO2 may cause acidification and emissions of NOx may cause eutrophication,
photochemical ozone formation and acidification. To decrease the environmental impact and
reach the goal of a sustainable society the Swedish Parliament has established 15
environmental quality objectives. To get a view over which of the objectives that are affected
by the flows from the system, the flows have been related to the environmental quality
objectives (Table 7).
Table 7: The different environmental flows from the system connected to the 15 environmental quality
objectives
Environmental flow
Environmental quality objectives
Resource use
Energy
Sand
Crushed rock
Emissions to air
SO2
NOx
CO
CO2
CH4
VOC
(VOC+NMVOC)
HC
N 2O
Particles
Emissions to water
COD
N-tot
Oil
Phenol
As
Cd
Secondary impact on: Reduced Climate Impact, A safe Radiation
Environment and Flourishing Lakes and streams
A Good Built Environment
A Good Built Environment
Clean Air and Natural Acidification Only
Clean Air, Natural Acidification Only, Zero Eutrophication and
Reduced Climate Impact
Secondary impact on: Reduced Climate Impact
Reduced Climate Impact
Reduced Climate Impact
Clean Air
Clean Air
Reduced Climate Impact
Clean Air
Flourishing Lakes and Streams
Zero Eutrophication and Flourishing Lakes and Streams
Flourishing Lakes and Streams
Flourishing Lakes and Streams
Flourishing Lakes and Streams
Flourishing Lakes and Streams
The resource use mainly affects the objective A Good Built Environment (Table 7). This
objective prescribes for example that the amount of disposed waste shall decrease with 50 %
from 1994 to 2005 and that 15 % of the utilisation of natural aggregates shall consist of
recycled material during year 2010. The emissions to air affect the four objectives Clean Air,
Zero Eutrophication, Natural Acidification Only and Reduced Climate Impact. The four
objectives direct a reduction of the content of particles, green house gases, hydrocarbons, SO2,
NOx, and VOC in the air. Finally, the emissions to water from the system affect mainly the
objective Flourishing Lakes and Streams. The objective Flourishing Lakes and Streams was
established to improve the qualities of surface waters by for example decreasing the load of
nutrients in lakes and streams and prevent that emissions like heavy metals will reach the
water.22
22
www.miljomal.nu
29
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
6.2.2 Differences in resource use and emissions
The scenarios differ in their resource use and emissions (Table 8). The data on the flows were
also normalized by division with the Swedish national flow per person and year and
multiplied with a factor of 1000 (Table 8). The National values per person in Sweden were
taken from the progressing research by Olsson et al (2004).
Table 8: Flows from the three different scenarios, and their normalized values. Scenario 1, MSWI bottom ash
used as drainage material in a covering structure in a landfill. Scenario 2, MSWI bottom ash used as sub-base
material in road. Scenario 3, disposal of MSWI bottom ash.
Substance
flow
Resource
use 1
Energy
[MJ]
Sand
[tonnes]
Crushed
rock
[tonnes]
Emissions
to air 2
SO2 [g]
NOx [g]
CO [g]
CO2 [g]
CH4 [g]
VOC [g]
Scenario
1
Scenario
2
Scenario
3
National
values
per
person
Normalized
values
scenario 1
Normalized
values
scenario 2
Normalized
values
scenario 3
269
79
139
250000
1,1
0,3
0,6
0
0,9
0,9
2,5
0
360
360
1,2
0,3
1,2
4,4
266
73
266
6
91
14
11590
0,01
2
36
5,6
4570
0,004
3
48
7,2
6030
0,007
6450
26900
85900
6180000
634000
0,9
3,4
0,2
1,9
0,00002
0,4
1,3
0,1
0,7
0,000006
0,5
1,8
0,1
1,0
0,00001
(VOC+NM
VOC)
0,04
0,008
0,03
667000
0,00005
0,00001
0,00004
HC [g]
5,9
2,4
3,2
No data
No data
No data
No data
N2O [g]
0,2
0,09
0,1
930000
0,0003
0,0001
0,0001
Particles
[g]
2,0
0,8
1,3
9730
0,2
0,1
0,1
Emissions
to water 3
COD [g]
0,2
0,07
0,09
56000
0,003
0,001
0,002
Ntot [g]
0,03
0,01
0,02
2800
0,01
0,004
0,005
Oil [g]
0,06
0,02
0,03
No data
No data
No data
No data
Phenol [g]
0,08
0,03
0,04
No data
No data
No data
No data
As [g]
0,1
0,4
0,4
No data
No data
No data
No data
Cd [g]
0,04
0,01
0,01
0,07
596
190
175
Cr [g]
0,5
0,2
0,2
1,4
335
173
167
Cu [g]
43
2,0
0,2
20
2127
98
10
Ni [g]
0,8
0,3
0,3
1,4
558
185
177
Pb [g]
0,3
0,2
0,2
4,3
71
56
55
Zn [g]
1,8
2,4
2,4
49
37
49
49
1) National values based on official statistics 2003. These values are divided by the total amount of inhabitants in
Sweden 2003. The national value for sand value is taken from SGU (2003).
2) National values are based on official statistics 2002 for emissions to air; these values are divided by the total
amount of inhabitants in Sweden 2003.
3) National values are based on official statistics 2000 for emissions from municipal wastewater treatment
plants, pulp and paper industry and some other coastal-based industries in Sweden.
30
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
The normalization results in Table 8 show that some environmental flows may be considered
more important than others. The use of sand and crushed rock and the release of metals were
of greater significance than other flows. The release of metals is according to the normalized
values the most important environment flow in scenario 1. This depends on the fact that the
MSWI bottom ash is in contact with a significantly higher amount of water than in the other
scenarios (see section 6.2.3). The use of natural aggregates is of higher significance than the
use of energy. Scenario 1 generates more emissions in almost every flow. This can be
explained by the fact that scenario 1 have the highest energy use. All investigated emissions,
except the release of metals are caused by energy use. Since scenario 1 uses most energy, it is
also causing the most energy-dependent emissions. There are two main reasons to a high
energy use in scenario 1, firstly long transports of the MSWI bottom ash, secondly production
of geofabric to the drainage layer and crushed rock to the conventional road, see section 6.2.4.
Scenario 2 has the lowest flow of energy-dependent emissions.
The result (Table 8) is based on the fact that the production of machines is not included in the
system. The environmental impact due to production of machines was investigated for a part
of the system, production of material, construction, and use and maintenance of a drainage
layer of MSWI bottom ash. It was discovered that the production of machineries did not have
a significant effect on the final result except for particles (see Appendix 3). According to the
method, life cycle stages that do not have a significant effect on the system can be excluded.
A second reason for excluding the production of machines was that it was hard to find data
about machine use during production of crushed rock. However, it should be noted that the
flow changes to some extent if the production of machines is included; the biggest changes
are the amount of particles. The particles increase with 20 %, the reason to this is that the
machines were assumed to be made of steel and the production of steel has a high emission
factor for particles. The barrier layer in scenario 3 is also excluded from the system, due to
lack of realistic data for the production of geosynthetic clay liners. To give a view of how
much the use of geosynthetic clay liner affects the result, data for mining of magnetite ore
were used as a substitute for data of bentonite mining. The result showed that there were
almost no changes of the result when the geosynthetic clay liner was included in the system
(Appendix 3).
6.2.3 Use of natural aggregates
According to the normalized values, the use of sand and crushed rock was of higher
importance than other types of flow such as emission to air and energy use. All scenarios use
natural aggregates, but scenario 2 has the highest flows since the MSWI bottom in this
scenario is not substituting any conventional material.
6.2.4 Leaching of metals
The leaching from the system during the next coming 100 years can be seen in Figure 17.
31
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
Metal leaching, 100 years
Scenario 1
100
Total amount leached (g)
Scenario 2
Scenario 3
10
1
0,1
0,01
0,001
As
Cd
Cr
Cu
Ni
Pb
Zn
Figure 17: The leaching from the system during 100 years.
Scenario 1 has the highest emissions of all metals except for Arsenic (As) and Zinc (Zn)
(Figure 17). This depends on that the MSWI bottom ash is in contact with a significantly
higher amount of water than in the other scenarios. The drainage layer is built to direct upper
rain and is assumed to have an infiltration through the layer of approximately 200 mm per
year. The road has an infiltration rate of 15 mm per year. In L/S-test the leaching partly is
dependent on the substances that are connected to organic material. Since Copper (Cu) is
bound to organic material, the result shows a high amount of Copper. If the leaching had been
based on availably test instead, Zinc should probably have higher values than Copper since
the availability test is made at a very low pH. The low pH results in a dissolving of
hydroxides. Zinc is often bound to hydroxides, which explains the high values for Zinc from
availability tests.
It can be argued that for sand, the leaching of metals is the same as in natural conditions and
therefore should be excluded from the system. The metal leaching from the system when sand
is excluded can be seen in Figure 18.
Metal leaching, 100 years,
sand excluded
Scenario 1
Scenario 2
Total amount leached (g)
100
Scenario 3
10
1
0,1
0,01
0,001
As
Cd
Cr
Cu
Ni
Pb
Zn
Figure 18: Leaching from the system during 100 years, sand excluded
32
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
The differences between the scenarios are significantly bigger when the leaching from sand is
excluded from the system and those scenarios that contain sand (scenario 2 and 3) have a
large decrease in their total leaching.
6.2.5 Energy use
Energy is mainly derived from fossil fuel. Therefore, emissions to air and to some extent
emissions to water, depend on the amount of energy used during the different life cycle
stages. The energy consumption in the different life cycle stages is important for the relative
contribution to the overall environmental impact of each scenario. As can be seen in Figure 19
below, the life cycle stages that have the largest energy consumption are transports and
production of material in scenario 1. The reason to the long transports is that only two
landfills, Gatmots and Annelund, in Uppsala County will be finally covered before year 2008.
Since the ash is assumed to be produced in Uppsala city, this will result in relatively long
transports (55 km). Scenario 1 also includes a transport of geofabric from Germany.
However, even if the transport from Germany is taken away from the system, the energy use
for the transport of material in scenario 1 will still be the highest. The sand and the crushed
rock have a short transport distance to respective construction site (6 respective 20 km) due to
the high number of pits and quarries in Uppsala County.
Scenario 1
Energy use
Scenario 2
Scenario 3
Energy use [MJ]
250
200
150
100
50
0
Disposal of
MSWI-BA
Production of
material
Transport of
material
Construction
Total energy
consumption
Activity
Figure 19: Use of energy by each life cycle stages in the system
The high energy consumption during production of material in scenario 1 is mainly due to the
production of crushed rock needed for the conventional road but is also an effect of the
production of geofabric needed for the drainage layer. It can also be seen that the construction
stage has a small contribution to the total amount in all scenarios. It should also be noted that
the disposal of MSWI bottom ash has a small influence on the result.
It was discovered during the study that the MSWI bottom ash was sifted even if it will be
disposed in a landfill. Thus, sifting was a part of all scenarios and could therefore be
excluded. This information is dependent on the demand and price of recycled metals.
However, the sifting machine has also relatively high energy consumption. Based on this, a
comparison was made between sifting and non-sifting. It was shown that the energy
consumption for production of the drainage material respective sub-base material increased
with approximately 40 MJ/tonne MSWI bottom ash if the ash was sifted.
33
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Result
The energy used in the system is diesel and electricity. The percentage of each type is shown
in Figure 20. Here, it can be seen that scenario 3 has the highest percentage of electricity use,
mainly coming from production of crushed rock but also from production of chemicals
needed for cleaning of the leachate from the landfill during the first 20 years.
100%
90%
80%
70%
60%
Diesel
50%
Electricity
40%
30%
20%
10%
0%
scenario 1
scenario 2
scenario 3
Figure 20: The percentage of diesel and electricity use for each scenario
The transport distance for MSWI bottom ash, is a parameter that may vary considerably both
in scenario 1 and 2, since there is a limited amount of sources for the material. A sensitivity
analysis was performed for different transport distances for the MSWI bottom ash (Figure
21).
Energy consumption [MJ]
Total energy consumption,
scenario 1
Total energy consumption,
scenario 2
500
400
Total energy consumption,
scenario 3
300
200
Energy consumption, scenario 1
at varying distance
100
Energy consumption scenario 2,
at varying distance
0
0
20
40
60
80
100 120 140 160
Distance for transport of
MSWI-bottom ash [km]
Figure 21: Sensitivity analysis, distance for transports of MSWI bottom ash
It was shown that for scenario 2 the MSWI bottom ash can be transported 50 km before the
energy consumption is higher than the total energy consumption in scenario 3, and 120 km
before it is higher then scenario 1. Even if there is no transport of the ash scenario 1 would
still use more energy than the other two scenarios, due to high energy consumption in the
production of material. Hence, the transport distance was an important parameter for the
outcome of the comparison.
34
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Discussion
7. Discussion
7.1.1 Result
For all the environmental flows, scenario 2 was the most preferable, which depends mainly on
the amount of crushed rock in the remaining scenarios. The production of crushed rock is a
very energy consuming process and is the single process that affected the result the most. It
can also be argued that scenarios 1 and 3 to some extent suffers from that the system
boundaries imply that all scenarios always will be performed, since the result would be
different if the drainage-layer would be compared with another type of construction than a
road. The environmental impacts may have been even lower for scenario 2, if the base-course
layer not had been included in the system. It is sometimes argued that a thicker base-cause
layer is not needed for construction of a sub-base layer of MSWI bottom ash.23 The reason
why the base-course layer was included in this study was that all dimensions are taken from
the source for information, Törringevägen. However, these results depend strongly on the
chosen system boundaries and the assumption made during the inventory. The environmental
flows are also based on regional specific data and should therefore only be discussed in
general. The flows would be different if the scenarios were realised in a geographically
disparate region. If the result from the study is to be used in other cases, corrections should be
made for important parameters such as transport distances, different methods for extraction of
natural resources and the amount of precipitation.
Differences in resource use and emissions
Usually leaching of metals is the only flow considered in environmental assessments of
alternative materials. According to the normalization result, it is reasonable to consider
leaching as an important flow, but the other consequences caused by the substitution of
material for example energy use and utilisation of natural aggregates should not be neglected.
It should be noted that the total amount of leached metals is almost the same in all scenarios
(even in scenario 3 that only includes conventional material). This indicates that other factors
than leaching should be discussed during utilisation of different residuals. Perhaps future
studies would wish to concern health aspects more deeply, should machineries not be
excluded, since these particles from machine operation affect the human health.
During the study, there have been discussions whether the barrier layer should be included in
scenario 1 or not. The reason is that traditionally the barrier layer in the cover structure often
contained the clay bentonite. According to RVF (2001), there are two big threats for the
chemical stability of a barrier layer containing bentonite, very low or high pH in the infiltrated
water, or if the water has high chloride content. The MSWI bottom ash’s high content of
chloride leads to increased permeability of the barrier layer and therefore ash is sometimes not
recommended to be used together with a barrier layer of bentonite. According to the Swedish
Geotechnical Institute the increased permeability of the barrier layer is relatively small, and
will therefore not have a significant affect on the leaching from the landfill. This
recommendation is only valid for landfills without hazardous waste.24 Natural clay is here an
alternative to use a barrier layer containing bentonite. However, the natural clay has more
negative qualities than barrier layers containing bentonite. Natural clay is also very seldom
used for this type of constructions in Sweden. The final decision was to use a geosynthetic
23
24
Reference group, personal communication
Rogbeck, personal communication
35
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Discussion
clay liner (consists of geofabric and bentonite) as a barrier layer. The results would have
become different if the natural clay had been chosen.
Use of natural aggregates
About 70 million tonnes of natural aggregates are used every year in Sweden for road and
ground constructions (SGU, 2003). At the same time industries produce large quantities of
secondary products, which may be suitable for use. One of the barriers to the wide-ranging
utilisation of the secondary products from energy production has been uncertainty about the
environmental impacts. Because of the risk of that secondary products could leach toxic
substances into the nearby environment. Therefore, the environmental evaluation mainly has
focus on measurements of total chemical content and leaching behaviour. According to the
normalized values from this study, it should be reasonable to also consider decreased use of
natural aggregates in future evaluation of residuals. Another incentive to consider the use of
natural aggregates is the objective A Good Built Environment that prescribes that 15 % of the
utilisation of natural aggregates shall consist of recycled material year 2010.25
Leaching of metals
According to the normalized values given in Table 8, the leaching of metals is an important
parameter. This conclusion is however to some extent uncertain, since in practice numerous
factors e.g. the conditions of the structure and its surface as well as the environment
conditions, affect leaching. According to Nyhlén (2004), the standardised tests cannot fully
reflect these factors. For example the batch test will not show what will happen if the
parameters such as pH and redox potential change. The test gives only information about the
average concentration in the leaching water and nothing about the variation over time.
Therefore, long-term predictions of the effect on the environment based on this type of test
contain a high degree of uncertainty. However, the leaching test is toady the best available
tool to predict leaching, if you are aware of the defects and uncertainties associated with them.
The importance of the metal flows can also be proven by the fact that it is the only outflow
leaving the system during 100 years; the remaining flows are “one time outflows” and occur
only during production respectively the construction stage. If the leaching is such an
important parameter it would be interesting to investigate if cleaning of the MSWI bottom ash
is motivated. There are several kinds of recycling methods to reuse the metals in the ash. By
cleaning the ash, the amount of metals leaching from the system will be reduced.
A low L/S ratio also allows little water to get in contact with the material. Scenario 1 includes
a high amount of infiltrated water; this conveys that value of L/S 10 is reached after only 7
years. The leaching value that corresponds to 7 years is then multiplied to be representative
for 100 years. This is a very rough estimation and higher L/S ratios would have been
preferable, but were not found. There were also uncertainties in selection of infiltration rate,
because of the high dependence of the precipitation. Here, all the infiltrated water was
assumed to be in contact with the ash, which probably is an over estimation since it is likely
that the water will be heterogeneously distributed. Due to the overestimations, the leaching
values in reality are probably lower in all the scenarios.
Energy use
Energy is one of the main resources used by the system. The result from the study is
dependent on the case-specific data and are affected by the construction itself and the
processes included, such as pre-treatment of the materials, transportation and the construction.
25
www.miljomal.nu
36
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Discussion
In this case, the transports had a key role; in other geographical regions the result may be
different. The reason to this is for example that the number of sand pits and rock quarries is
high in Uppsala County.
For scenario 1 the most preferable situation is that the MSWI bottom is used on the same site
where it is sifted, to reduce the transport-distance. Scenario 2 is not to the same degree
dependent of the transport-distance for the MSWI bottom ash, but maximum distance should
be 50 km.
7.1.2 Method
ESA with an LCA-approach
The utilisation of residuals is normally environmentally evaluated from a narrow perspective
of the material itself, mainly studied by leaching tests. This type of evaluation consists of
chemical analysis for determination of total content, and what can possibly leach out from the
residuals. The ESA allowed both resource use and emissions to be considered, thereby giving
a different and wider result than a more narrow study. The LCA-approach is often criticized
for being an uncertain method with a lot of assumptions and predictions. However, it is
important to clearly describe assumptions and weaknesses in the analysis and that sensitivity
analysis is continuously carried out during the ESA-process. Today, the LCA within an ESA
probably is one of the best available methods to investigate complex systems such as the
waste handling system in a region.
In this thesis there has been a decision to only present the different flows in a non-aggregated
form in the different scenarios and leave a further valuation to the decision makers. It can be
discussed if this is right or wrong. Since a big amount of parameters can make the result
complex and difficult to interpret, a valuation can be a helpful tool to reduce the number of
parameters. According to Rydh et al (2002), a valuation can also be uncertain, since it is
dependent on the system boundaries. The different weighing-methods also describe something
that in general is not accepted though they are based on different valuations for example
individual, political and or moral. For a decision-maker, it is easier to handle aggregated
parameters, but the more aggregated value the more uncertain. To handle this problem, the
flows were normalised, meaning that the values are to some extent aggregated but not totally
valuated. The method used in this thesis gives a presentation of the flows that can be
considered as important flows. However, which utilisation scenario is the most preferable one
depends on which environmental quality objectives are prioritised. The project of Värmeforsk
(Q248) will go more deeply into this question.
System boundaries
The primary interest was not to analyse the environmental impact from the incinerationprocess and the production-processes generating the MSWI bottom ash have therefore been
excluded from the study. A relevant question is in what way the choice of excluding the
production-process, and thereby considering the ash as a waste, has influenced the result?
Roth and Eklund (2003) say that this kind of decision certainly affects the outcome of the
study and favours the residuals and the excluded effects could sometimes be dominating
environmental flows. Therefore, it is important to remember that no conclusions about
possible environmental benefits or disadvantages during incineration of municipal solid waste
can be drawn from this study. The demolition phases for the road and landfill were not
considered due to the fact that demolitions of these kinds of constructions are rather rare
today. However, there are progressing discussions about how to recycle the material in old
37
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Discussion
roads and landfills and in further studies this life cycle stage should be included. Use of
geofabric would facilitate the recycling of the material after demolition, but it should be noted
that the result showed that production of geofabric is one of the most energy-consuming
processes within the system.
It seems that the ESA-approach has some limitations regarding those flows that are strongly
related to the time frame used, for example the leaching. According to Finnveden and Nielsen
(1999), the environmental impacts from landfills can be seriously underestimated if the period
after 100 years is neglected. Some elements in the ash can be transported to the water phase
and then leach comparatively quickly while others have a slower emission rate. Leaching of
soluble salts will gradually change the chemical compositions of the ash. For example the pH
can change even after a fairly long time period. If the pH changes, the solubility of different
minerals will change and consequently there will be a change in the composition of leachate.
It may be argued that the landfill is a part of the technical system for a certain time period.
Leaching on an infinite time scale is of limited interest. This is since the environmental
impacts from metals often are due to peaks in concentration rather then average emissions
(Olsson et al, 2004).
Inventory
New life cycle data for disposal of materials were collected during the inventory phase, which
is valuable since previous data for the different environmental impact from disposal of
materials were old and since there was a lack of important data such as the environment
impact connected to the covering structure of the landfill. The ambition has been to use data
that are region specific and as up-to-date as possible. To decrease the uncertainties, it would
be of help to have access to more detailed data, especially for machineries, production of
geosynthetic clay liner and also leaching parameters for the different materials.
7.1.3 Proposals for future research
•
To expand the scenarios of utilisation areas for MSWI bottom ash – for example, in a
pre-covering layer of a landfill or as a filling material.
•
To include a demolition phase for the road and the landfill in the study.
•
To investigate other possible secondary materials that may be used as drainage
material –this can provide good information for comparing purposes.
•
To complement the study with a socioeconomic perspective – can it be motivated from
a socioeconomic point of view to clean MSWI bottom ash?
38
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Conclusions
8. Conclusions
According to this study, the use of MSWI bottom ash in the sub-base layer in road
construction is more environmentally preferable, compared to use the MSWI bottom-ash as
drainage material in a landfill structure or to dispose of the ash. Use of the MSWI bottom ash
in the sub-base layer in a road would lead to the use of less resources such as use of natural
aggregates and energy. This also means less energy-derived emissions. The single process
that affected the result most was production of crushed rock due to the very high energy
consumption connected to this process. It was shown that scenario 1 and 3 to some extent
suffer from that the system boundaries imply that all scenarios always are performed since the
result would be different if the drainage-layer would be compared with other types of
construction than a road. Parameters with potential to change the result are: transportdistances that are dependent on the regional conditions and metal leaching, where the current
leaching test only is an approximation of leaching over time and though not reflect all
processes that will affect the leaching. Besides these results, new life cycle data for disposal
of material was collected. Previously existing values for the environmental impact of material
disposal were old and lacked important information such as the environment impact
connected to the covering structure of the landfill. However, the results are strongly
dependent on the chosen system boundaries and the assumptions made during the inventory.
The ESA approach allowed both resource use and emissions to be considered and can
therefore be seen as a valuable complement to other studies that use a more narrow system
perspective. The results can be used to obtain information for decision support concerning
waste management.
39
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
References
9. References
Literature
Alvarez, H. (1999) Energiteknik. Studentlitteratur, Lund (In Swedish).
Arm, M. (2003) Mechanical Properties of Residues as Unbound Road Materials –
experimental tests on MSWI bottom ash, crushed concrete and blast furnace slag. Doctoral
Thesis, Royal Institute of Technology, Stockholm.
Bjurström, H. (2002) En bedömning av askvolymer. Not published, Svenska Energiaskor AB,
Stockholm, (In Swedish).
City of Helsinki, Real Estate Department. (1983) Användning av stenkolaska vid
anläggningsarebeten, tekniska anvisningar. Helsinki.
County Administrative Board in Uppsala. (2004) Avfallshantering I Uppsala län –
Behandlingsbehov och behandlingskapacitet år 2002 och 2009. Länsyrelsens meddelande
2004:2, (In Swedish).
Ek, M. & Sundqvist, J. (1998) Skogsindusriellt avfall, ideér angånde utnyttjande och
omhändertagande. IVL Swedish Environmental Research Institute, Stockholm, (In Swedish).
Ek, M. & Westling, O. (2003) Dagsläget beträffande skogsindustrins avfall. IVL Swedish
Environmental Research Institute AB, Stockholm, (In Swedish).
Eriksson, M. (2001) Alternativa fyllningsmaterial till ledningsgravar för VA- en jämförelse
mellan nya och traditionella material. Degree thesis, Royal Institute of Technology,
Stockholm, (In Swedish with an English summary).
Finnveden, G., Nielsen, P. (1999) Long-Term Emissions from Landfills Should Not be
Disregarded. Int. J. LCA 4 (3), 125-126.
Hernhag, C., Holmberg, C., Almqvist., Deloche, Y. (2003) Treatment options for waste fly
ash. Not published, Vattenfall Värme Uppsala AB, Uppsala.
Kärrman, E., Moeffaert, D., Bjurström, H., Berg, M., Svedberg, B. (2004) Förutsättnigar för
att askor kommer till användning i vägar. Thermal Engineering Research Institute
(Värmeforsk), (In Swedish).
Larsson, M., Lejon, A. (2003) Cementstabiliserad granulerad flygaska och dess tekniska
egenskaper. Degree thesis, Luleå University of Technology, Luleå, (In Swedish with an
English summary).
Lin, K., Wang, K., Tzeng, B., Lin, C. (2002) The reuse of municipal solid waste incinerator
fly ash slag as a cement substitute., Resources, Conservation and Recycling 39, 315-324.
Mácsik, J. (2004) Pilotförsök med flygstabiliserat avloppsslam (FSA) som tätskikt. Thermal
Engineering Research Institute (Värmeforsk), (In Swedish with an English summary).
40
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
References
Moberg, Å., Finnveden, G., Johansson, J., Steen P. (1999): Miljösystemanalytiska verktyg –
en introduktion med koppling till beslutssituationer. The Swedish Environmental Protection
Agency, Stockholm, (In Swedish).
Mroueh, U., Eskola, P., Laine-Ylijoki, J. (2001) Life-cycle impacts of the use of industrial byproducts in road and earth construction. Waste Management 21, 271-277.
Mäkelä, H., Höynälä, H. (2000) By-products and Recycled Materials in Earth Structures –
Material and Applications. National Technology Agency, Helsinki.
Nyhlén, E., (2004): Laktester för riskbedömning av förorenad mark. Degree thesis, Swedish
University of Agricultural Sciences, Uppsala, (In Swedish with an English summary).
Olsson, S., Kärrman, E., Gustafsson, J.P. (2004) Environmental systems analysis
of the use of bottom ash from incineration of municipal waste for road construction.
Proceedings of the 19th International Conference on Solid Waste Technology and
Management, March 21-24, 2004, Philadelphia, PA USA.
Peterson, A. (2004) Miljösystem analys för alternativa lättfyllnadsmaterial i vägar. Degree
thesis, Royal Institute of Technology, Stockholm, (In Swedish with an English summary).
Brundin, H., Kihl, A., Lagerkvist, A., Pusch, R., Rihm, T., Sjöblom, R., Tham, G. (2001)
Långtidsegenskaper hos tätskikt innehållande bentonit. The Swedish Association of Waste
Management, RVF 01:12, (In Swedish).
Roth, L., Eklund, M. (2002) Environmental evaluation of reuse of by-products as road
construction materials in Sweden. Waste Management 23, 107-116.
RVF (The Swedish Association of Waste Management). (2002) Kvalitetssäkring av slaggrus
från förbränning av avfall. RVF 02:10, (In Swedish).
Rydh, C., Lindahl, M., Tingström, J., (2002): Livscykelanalys – en metod för miljöbedömning
av produkter och tjänster. Studentlitteratur, Lund, (In Swedish).
SETAC-Europé. (1999) Best Available Practice Regarding Impact Categories and Category
Indicators in Life Cycle Assessment. Int. J. LCA 4 (3), 167-174, Brussels.
SGI (Swedish Geotechnical Institute). (2003) Inventering av restprodukter som kan utgöra
ersättningsmaterial för naturgrus och bergkross i anläggningsbyggande. Linköping, (In
Swedish, with an English summary).
SGU (Geological Survey of Sweden). (2003) Aggregates – roduction and resources 2002.
SGU 2003:4, Uppsala, (In Swedish, with an English summary).
Sonesson, U., Dalemo, M., Mingarini, K., Jönsson, H. (1997) ORWARE – A simulation model
for organic waste handling systems. Part 2: Case study and simulation results. Resources,
Conservation and Recycling 21, 17-37.
41
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
References
SS-EN-ISO 14040. (1997) Environmental management- Life cycle assessment- Principles and
framework. ISO14040:1997, Swedish Standards Institutions, Stockholm.
Strand, A. (2003) Life cycle assessment for manufacturing stainless steel – a cradle to gate
study for Avesta Polarit AB in Avesta. Degree thesis, Högskolan Dalarna, Borlänge, (In
Swedish with an English summary).
Stripple, H. (2001) Livscykelanalys av väg - En modellstudie för inventering. Swedish
Environmental Research Institute (IVL), Göteborg, (In Swedish with an English summary).
Sundberg, J., Carling, M., Ländell, M., Svensson, B. (2003) Täckning av deponier med
blandning av avloppslam och aska, erfarenheter, beständighet och andra egenskaper. The
Swedish Water & Wastewater Association, Stockholm, (In Swedish).
Svingby, M., Båtelsson, O. (1999) LCA av lättfyllnadsmaterial för vägbankar. National Road
Administration, Vägverket1999:67, Borlänge, (In Swedish).
Vattenfall Värme Uppsala AB. (2003) Miljörapport Uppsala 2003, (In Swedish).
Personal references
Bjurström Henrik, ÅF, Stockholm
Burton George, Texas Sodium Bentonite Inc., Houston, USA
Eklund Urban, ENA Kraft AB, Enköping
Ericson Johan, Vattenfall Värme AB, Uppsala
Johansson Eddie, ENA Kraft AB, Enköping
Kjällman Magnus, VA och Avfallskontoret, Uppsala Kommun, Uppsala
Laurell Johan, VA och Avfallskontoret, Uppsala Kommun, Uppsala
Mácsik Josef, Ecoloop, Stockholm
Munde Hanna, Vattenfall Värme AB, Uppsala
Reference group for the project by Värmeforsk (Q 248), meeting at Ramböll Sverige AB,
2004-10-21
Rogbeck Jan, Statens Geotekniska Institut, Linköping
Sjöholm Markus, Gävle Vägtrummor AB, Gävle
Strömbäck Niklas, Vattenfall AB Värme Norden Små och Stora Anläggningar, Knivsta
Tham Gustav, Telge Återvinning AB, Södertälje
42
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
References
Internet
Econova AB. (2003) The Econova Method. Available: www.econova.se [2004, September 13]
Environment Objectives Secretariat. (2004) Environmental Quality Objectives. Available:
www.miljomal.nu [2004, November 3]
Swedish Environmental Protection Agency. (No date) Environmental Objectives. Available:
www.naurvardsverket.se [2004, November 5]
43
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 1
Appendix 1
A1.1 System boundaries for each scenario
Scenario 1: MSWI bottom ash as drainage material in a covering structure in a landfill
MSWI
bottom ash
Crushed
granite
Production of
drainage material
Production of sub-base and
base-course material
Construction of
drainage layer
Construction of sub-base
and base-course layers
Use and
maintenance of
drainage layer for
100 years
Use and maintenance of
the road for 100 years
Figure A1: System boundaries, scenario 1, MSWI bottom ash as drainage material in a covering structure in a
landfill
Scenario 2: MSWI bottom ash as sub-base material in road construction
Sand
MSWI
bottom ash
Production of
drainage material
Production of sub-base
and base-course material
Construction of
drainage layer
Construction of sub-base
and base-course layers
Use and
maintenance of
drainage layer for
100 years
Use and maintenance of
the road for 100 years
Figure A2: System boundaries, scenario 2, MSWI bottom as sub-base material
in road construction
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 1
Scenario 3: Disposal of MSWI bottom ash
Sand
Crushed
granite
Production of
drainage material
Production of sub-base
and base-course material
Construction of
drainage layer
Construction of sub-base
and base-course layers
Use and
maintenance of
drainage layer for
100 years
Use and maintenance of
the road for 100 years
MSWI
bottom
ash
Waste
disposal
Figure A3: System boundaries, scenario 3, disposal of MSWI bottom ash
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Appendix 2
A2.1 Inventory
A2.1.1 General data
Material
Value
Density of crushed rock (non-packed)
Density of crushed rock (packed in sub base or base-course layer of a
road)
Density of MSWI BA generally, (packed)
Density of MSWI BA from Vattenfall, (packed)
Density of MSWI BA from Vattenfall, (non-packed)
Density of sand (Stallmon)
Density of excavated soil
Density of soil
Weight of geofabric (in geosynthetic clay liner)
Weight of bentonite (in geosynthetic clay liner)
Percentage of bentonite in geosynthetic clay liner
Percentage of geofabric in geosynthetic clay liners
Weight of geofabric
Density of geofabric
Density of geofabric (in geosynthetic clay liner)
Density of bentonite (in geosynthetic clay liner)
Energy
Energy content in diesel
Pre-combustion diesel
Energy consumption during loading, (light density)
Energy consumption during loading, (high density)
Diesel use by transporting lorry (max load 35 tonnes, halfway full and
halfway empty assumed)
Use of diesel during excavating of material with excavator (material
density 1.4-1.6 tonnes/m3) (Volvo EC240)
Use of diesel during excavating sand with loading shovel (Volvo L180E)
Use of diesel by sifting machine
Use of electricity per tonne sifted MSWI BA
Use of diesel by crushing rock
Use of electricity for crushing rock
Energy use for road production
Energy use for road production
Unit
Reference
1,62
tonnes/m3
Stripple, 2001
2,0
1,6
1,6
1,4
1,6
1,42
1,68
110
4600
95
5
150
83,333333
366,66667
807,01754
tonns/m3
tonnes/m3
tonnes/m3
tonnes/m3
tonnes/m3
tonnes/m3
tonnes/m3
g/m2
g/m2
%
%
g/m2
kg/m3
kg/m3
kg/m3
Olsson et al, 2003
RVF, 2002
Vattenfall Värme Uppsala AB
Vattenfall Värme Uppsala AB
Jehanders Grus AB
Stripple, 2001
Stripple, 2001
www.naue.com 2003
www.naue.com 2003
Gävle Vägtrummor AB
Gävle Vägtrummor AB
www.naue.com 2004
www.naue.com 2004
www.naue.com 2003
www.naue.com 2003
Value
Unit
Reference
35,1
0,1
1,72
3
MJ/l
MJ/MJ oil or diesel
MJ/m3 loaded material
MJ/m3 loaded material
Stripple, 2001
Stripple, 2001
Stripple, 2001
Stripple, 2001
0,45
l/km
Jehanders Grus AB
10,75
21,25
1,0416667
2,006
0,484
21,19
7,02
0,083333
l/h
l/h
l/tonne MSWI BA
kWh/tonne sifted MSWI BA
l/tonne crushed rock
MJ/tonne crushed rock
MJ/ton
l/tonne material
Swecon Anläggningsmaskiner AB
Jehanders Grus AB
Slag Recycling AB
SYSAV, Malmö
Stripple, 2001
Stripple, 2001
Stripple, 2001
Värmdö schaktmaskiner AB, Järfälla
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Precipitation and infiltration
Value
Precipitation in Uppsala per year
Infiltration on landfill top layer
Infiltration through asphalt layer in a road
509
40
0,015
Landfill parameters
Value
Thickness of drainage layer (both with sand and MSWI BA)
Thickness of vegetation (soil) layer
Thickness of surface layer
Thickness of drainage layer
Thickness of geofabric
Thickness of barrier layer, geosynthetic clay liner
Thickness of geofabric, in geosynthetic clay liner
Thickness of bentonite, in geosynthetic clay liner
Thickness of pre-covering layer
Thickness of the landfill
Max water going through the landfill
Amount of cleaned leachate water per year
Use of NaOH for water treatment
Use of iron chloride (PIX-111) for water treatment
0,1
1,35
0,5
0,1
0,0018
0,006
0,0003
0,0057
0,2
15
50
67274
10
22
Unit
Reference
l/m2
% of precipitation
tonne/m3
Uppsala Kommun VA- och Avfallskontoret, 2003
Assumption
Assumption
Unit
m
m
m
m
m
m
m
m
m
m
l/m2 and yr
tonnes/yr
tonnes/year
tonnes/year
Reference
Ecoloop
Ecoloop
Ecoloop
Ecoloop
www.naue.com 2004
www.naue.com 2003
www.naue.com 2003
www.naue.com 2003
Ecoloop
Ecoloop
Ecoloop
Uppsala Kommun VA- och Avfallskontoret, 2003
Uppsala Kommun VA- och Avfallskontoret, 2003
Uppsala Kommun VA- och Avfallskontoret, 2003
A2.1.2 Factors for resources use
Processes
Combustion of 1 MJ diesel in working
machine
Combustion of 1 MJ diesel during
transport
Pre-combustion of 1MJ diesel
Production of 1 MJ electricity
Combustion of 1MJ diesel in loading
shovel (Volvo L180)
Combustion of 1 MJ diesel in excavator
Production of 1 kg geofabric
Production of 1 kg steel
Production of 1kg NaOH
Production of 1 kg Iron cloride (PIX-111)
Production of 1 kg bentonite (mining of 1
kg magnetite ore)
Reference
Oil
(MJ)
Biofuel
(MJ)
Stripple, 2001
1
Stripple, 2001
Stripple, 2001
Stripple, 2001
1
0,1
0,06
Stripple, 2001
Stripple, 2001
Svingby and
Båtelsson, 1999
Stripple, 2001
Wallén,
Almemark et al,
2003
Almemark et al,
2003
Peat
(MJ)
Coal
(MJ)
Natural
gas (MJ)
Uranium
(MJ)
Water
power
(MJ)
0,05
0,005
0,04
0,009
1,6
0,47
0,189
0,02
0,039
1, 8
0,016
6,7
1,974
2,8
0,8225
Iron
(g)
Crude
oil (g)
Water
(g)
Waste
(g)
0,07
1,1
1,1
11,2
3,6
0,15
0,0788
0,008
11,1
15,3
0,07
0,13
0,002
0,0002
0,002
0,28
0,07
0,0204
0,043
0,013
0,001
0,01
0,003
0,48
0,140
1100
0,29
1000
784
0,12
0,006
0,02
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
A2.1.3 Factors for emission to air
Process
Combustion of 1 MJ diesel in
working machine
Combustion of 1 MJ diesel during
transport
Pre-combustion of 1MJ diesel
Production of 1 MJ electricity
Combustion of 1MJ diesel in loading
shovel (Volvo L180)
Combustion of 1 MJ diesel in
excavator
Production of 1 kg geofabric
Production of 1 kg steel
Production of 1 kg NaOH
Production of 1 kg Iron cloride (PIX111)
Reference
SO2 (g)
(air)
CO2
(g)
(air)
Nox
(g)
(air)
CO (g)
(air)
HC
(g)
(air)
CH4
(g)
(air)
N2O
(g)
(air)
VOC (g)
(air)
Particles
(g) (air)
COD
(g)
(aq)
N-tot
(g)
(aq)
Oil
(g)
(aq)
0,00
04
Stripple, 2001
0,02
75
0,7
0,09
0,04
0,0001
0,002
0,03
Stripple, 2001
0,02
75
0,6
0,1
0,03
0,0001
0,002
0,01
Stripple, 2001
Stripple, 2001
0,01
0,007
4
3,8
0,004
0,009
0,0001
0,002
0,01
0,0012
0,0002
0,0001
0,0004
0,0005
0,00007
Stripple, 2001
0,04
79
0,7
0,09
0,05
0,0001
0,002
0,03
0,0012
0,0002
Stripple, 2001
Svingby and
Båtelsson, 1999
Stripple, 2001
Wallén, 1999
Almemark et al,
2003
0,04
79
0,7
0,09
0,05
0,0001
0,002
0,03
0,0012
0,0002
0,028
7,34
0,013
16
2200
9,38
0,04
4,86
0,04
0,0003
39
0,001
0,007
0,17
0,0004
0,0018
0,03
0,0008
1,83E05
0,009
0,02
0,0006
9,1
0,0002
6,09E06
0,005
1,2
0,0019
0,0003
0,01
1
0,0066
9,13E05
4,78E-05
3,04E-06
0,001
0,00
04
0,00
04
Phenols
(g) (aq)
0,0006
0,0006
0,0006
A2.1.4 Factors for emissions to water
Process
Potential leaching (all available) from MSWI BA (Nordtest
NT ENVIR 003)
Lechate from 1 tonne MSWI BA (L/S 2) CEN-method
Lechate from 1 tonne MSWI BA (L/S 10) CEN-method
Lechate from 1 tonne sand (L/S 2), method CEN prEN
12457
Lechate from 1 tonne sand (L/S 10), method CEN prEN
12457
Potential leaching (all available) from crushed rock
(Nordtest NT ENVIR 003 with some modification)
Lechate from 1 tonne crushed rock (L/S 2) (CEN 8361),
fresh material
Potential leaching (all available) from sand (NT ENVIR
003)
Reference
RVF, 2002
RVF, 2002
RVF, 2002
Cl (g)
(aq)
3375
1617
1856
SO4 (g)
(aq)
1617
3375
7518
As (g)
(aq)
Cd (g)
(aq)
Cr (g)
(aq)
Cu (g)
(aq)
0,4
0,007
0,01
3,5
0,002
0,004
2,2
0,02
0,04
Mroueh et al, 2001
0,006
0,0002
Mroueh et al, 2001
Tossavainen and
Håkansson, 1999
Tossavainen and
Håkansson 1999
Gustafsson et al,
2003
0,03
1086
2,4
3,7
Ni (g)
(aq)
Pb (g)
(aq)
Zn (g)
(aq)
68,8
0,04
0,07
207
0,009
0,03
1766
0,067
0,15
0,004
0,004
0,004
0,04
0,001
0,02
0,02
0,02
0,2
0,2
0,04
0,3
0,16
1,5
0,35
2,8
0,008
0,0002
0,001
0,01
0,005
0,0006
0,007
1,7
0,03
0,2
0,46
1,2
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
A2.2 Calculations for case study
Data
Amount of water that infiltrates in drainage layer
Distance from MSWI BA production site to landfill
Amount of water that is contact with the MSWI BA in the drainage layer per
year
Amount of water that is contact with the MSWI BA in the landfill
Corresponding time to reach L/S 2 for MSWI BA drainage layer
Corresponding time to reach L/S 10 for MSWI BA drainage layer
Corresponding time to reach L/S 2 for MSWI BA in landfill
Corresponding time to reach L/S 10 for MSWI BA in landfill
Distance from sand production site to landfill
Amount of water that is contact with the sand in drainage layer per year
Corresponding time to reach L/S 2 (sand) in landfill drainage layer
Corresponding time to reach L/S 10 (sand) in landfill drainage layer
Amount of water that is in contact with the sand in pre-covering layer
Corresponding time to reach L/S 2 (sand) in landfill pre-covering layer
Corresponding time to reach L/S 10 (sand) in landfill pre-covering layer
Distance from MSWI BA production site to road
Distance from crushed rock production site to road
Distance from production site of geofabric and geosynthetic clay liner
MSWI BA road: Amount of water that is contact with the MSWI BA per year
MSWI BA road: Time to reach L/S 2 for sub base with MSWI BA
MSWI BA road: Time to reach L/S 10 or sub base with MSWI BA
MSWI BA road: Amount of water that is in contact with the crushed rock in
base course per year
MSWI BA road: time to reach L/S 2 for base course with crushed rock
MSWI BA road: time to reach L/S 10 base course with crushed rock
Crushed rock road: Amount of water that is contact with the crushed rock per
year
Crushed rock road: time to reach L/S 2
Crushed rock road: time to reach L/S 10
Value
0,20
55
1,45
0,002
1,38
6,88
960
4800
6
1,27
1,57
7,86
0,16
12,8
64
20
20
1225
0,02
99,2
496
5,0E-02
4,0E+01
2,0E+02
1,38E-02
1,5E+02
7,3E+02
Unit
tonnes/m2
km
tonnes water/ tonne
MSWI BA
tonne water/ tonne
disposed ash
years
years
years
years
km
tonnes water/ tonne
sand
years
years
tonnes water/ tonne
sand
years
years
km
km
km
tonne water/ tonne
MSWI BA
years
years
years
years
years
tonne water/ tonne
crushed rock
years
years
Note
Assume 60% evaporation
www.viamichelin.com . Average distance from Uppsala to landfill that
need drainage material
All MSWI BA assumed to have contact with infiltrated water and
assumed area is 1m2.
All MSWI BA assumed to have contact with infiltrated water
SGU, 2003. Average distance from Uppsala to sand pit
All sand assumed to have contact with infiltrated water and assumed
area are 1m2
All material assumed to have contact with infiltrated water
www.viamichelin.com
All material assumed to have contact with the infiltrated water
Assumed that all water that infiltrates will reach the material
Assumed that all water that infiltrates will reach the material
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
A2.2.1 Dimensions for the case study
Data
Use of MSWI bottom ash
Factor for amount of MSWI BA left after sifting 1 tonne
Volume drainage layer on a landfill that can be produced per tonne MSWI BA
Area of drainage layer
Use of geofabric, drainage layer
Use of sand for drainage layer
Use of soil for vegetation layer in landfill
Use of excavated soil for surface layer in landfill
Use of sand for drainage layer per tonne disposed ash
Use of clay for barrier layer
Use of geofabric barrier layer (in geosynthetic clay liner)
Use of bentonite, barrier layer (in geosynthetic clay liner)
Use of sand for pre-covering layer per tonne disposed ash
Length of road that can be produced per tonne MSWI BA
Use of crushed rock for MSWI BA road
Use of crushed rock for crushed rock road
Use of geofabric, barrier layer (in geosynthetic clay liner) per tonne disposed MSWI BA
Use of bentonite, barrier layer (in geosynthetic clay liner) per tonne disposed MSWI BA
Value
1
0,8
0,571428571
5,714285714
1,714285714
0,914285714
0,0756
0,023666667
0,005333333
4,285714286
1,257142857
26,28571429
0,010666667
0,153609831
0,322580645
1,172043011
0,003666667
0,153333333
Unit
tonne
tonnes
m3
m2
kg/unit drainage layer
tonnes sand/unit drainage layer
tonnes/tonne disposed MSWI BA
tonnes/tonne deposed MSWI BA
tonnes/tonne disposed MSWI BA
tonnes/unit drainage layer
kg/unit drainage layer
kg/unit drainage layer
tonnes/tonne disposed MSWI BA
m
tonnes
tonnes / unit road
kg/tonne disposed MSWI BA
kg/tonne disposed MSWI BA
A2.2.2 Energy use
Value
Activity
Production of drainage material from MSWI BA
Use of diesel during loading of sifted MSWI BA, alt A
Use of diesel during loading of sifted MSWI BA, alt B
Use of geofabric
Transport of MSWI BA from production site to
landfill (truck maxload 35 tonnes)
0,8196
0,9829
1,714
Unit
MJ/tonne MSWI BA
MJ/tonne MSWI BA
kg /tonnes MSWI BA
Oil (MJ)
Construction of drainage layer of MSWI BA
Use of diesel by excavator
79,426
MJ/tonne MSWI BA
3,7908
MJ/tonne MSWI BA
0,7187
MJ/tonnes MSWI BA
Peat
(MJ)
Coal
(MJ)
Natural
gas (MJ)
Uranium
(MJ)
Water
power
(MJ)
0,067
11,52
3,384
0,983
1,081
19,23
87,369
Diesel use, transport of MSWI BA
Diesel use, transport of geofabric
Bio
fuel
(MJ)
4,1698
0,8625
0,32
0,032
19,059
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Activity
Value
Unit
Oil (MJ)
Bio
fuel
(MJ)
Peat
(MJ)
Coal
(MJ)
Natural
gas (MJ)
Uranium
(MJ)
Water
power
(MJ)
Production of drainage material from sand (per unit
drainage layer produced with 1 tonne MSWI BA)
Use of diesel for excavating sand with loading shovel
(Volvo L180E) (includes loading)
0,8196
MJ/unit drainage layer
0,9836
9,902
MJ/unit drainage layer
0,7187
MJ/unit drainage layer
0,862
0,068
0,0136
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/ disposed MSWI
BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
MJ/tonne disposed
MSWI BA
kg NaOH/tonne
disposed MSWI BA
kg PIX-111 /tonne
disposed MSWI BA
5,48
6,8354
MJ/unit road
MJ/unit road
Transport of sand from production site to landfill
(per unit drainage layer that may be produced with 1
tonne MSWI BA) (truck maxload 35 tonnes)
Diesel use, transport of sand
Construction of drainage layer of sand
Use of diesel by excavator
Disposal of one tonne MSWI bottom ash
Diesel use during production of material to vegetation
layer
0,0566
Use of diesel during construction of vegetation layer
Diesel use for transport of soil to vegetation layer
Diesel use for construction of surface layer
0,0566
2,729
0,021
Diesel use for production of sand to drainage layer
0,0048
Diesel use for construction of drainage layer
0,0042
Use of diesel for transport of sand for drainage layer
Use of diesel for production of material to pre-covering
layer
Use of diesel for construction of pre-covering layer
0,0578
0,00956
0,008
Transport of sand for pre-covering layer
0,1155
Use of NaOH for cleaning of leachate water in 20 years
Use of PIX-111 (iron cloride) for cleaning of leachate
water in 20 years
Production of crushed rock to MSWI BA road
Use of diesel
Use of electricity
0,006
10,89
0,0679
3,0023
0,025
0,0057
0,0050
0,0635
0,011475
0,01
0,127
0,0009
0,0005
4,9E-05
0,0004
0,0001
0,0173
0,005
0,0018
3E-05
2,7E-06
2,4E-05
0,0038
0,0009
0,0003
6,03
0,437
0,3076
0,0308
0,2734
0,0636
10,937
3,2127
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Activity
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), alt A
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), alt B
Value
Unit
Oil (MJ)
3E-01
MJ/unit road
3,43E-01
0,597
MJ/unit road
0,7168
36,10
MJ/tonne MSWI BA
2,339990
64
MJ/tonne MSWI BA
Bio
fuel
(MJ)
Peat
(MJ)
Coal
(MJ)
Natural
gas (MJ)
Uranium
(MJ)
Water
power
(MJ)
0,23
39,73
11,67
Transport of MSWI BA from production site to road
(maxload 35 tonnes)
39,713
Diesel use
Construction of road of MSWI ash
Use of diesel for construction of sub base layer
2,5739
1,0379
Use of diesel for construction of base course layer
0,9435
MJ/unit road
19,911
24,83
MJ/unit road
MJ/unit road
21,902
1,589
1,04
MJ/unit road
1,14
2,17
MJ/unit road
2,39
36,1
MJ/tonne MSWI BA
Production of crushed rock to road with crushed
rock
Use of diesel
Use of electricity
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), Alt A
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), Alt B
Transport of crushed rock from production site to road
Use of diesel for road construction
3,4282
1,1176
0,111
0,9934
39,713
3,771
MJ/unit road
A2.2.3 Emissions to air
Activity
SO2 (g)
(air)
CO2 (g)
(air)
NOx (g)
(air)
CO (g)
(air)
HC (g)
(air)
CH4 (g)
(air)
N2O
(g)
(air)
VOC
(g)
(air)
H2S
(g)
(air)
PAH
(g)
(air)
Particles
(g) (air)
Production of drainage material from MSWI BA
Use of diesel during loading of sifted MSWI BA, alt A
0,0426
68,03
0,585
0,0698
0,0487
4,1E-05
0,0013
0,023
Use of diesel during loading of sifted MSWI BA, alt B
0,0373
77,65
0,70
0,08
0,0505
4,91-05
0,0016
0,02799
0,048
27,36
0,066
0,015
0,001
0,003
3,0182
6274,7
47,98
7,953
0,00397
0,127
Use of geofabric
Transport of MSWI BA from production site to
landfill (truck maxload 35 tonnes)
0,01
0,000504
0,832
Diesel use, transport of MSWI BA
3,05
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Activity
Diesel use , transport of geofabric
SO2 (g)
(air)
CO2 (g)
(air)
NOx (g)
(air)
CO (g)
(air)
HC (g)
(air)
CH4 (g)
(air)
N2O
(g)
(air)
VOC
(g)
(air)
H2S
(g)
(air)
PAH
(g)
(air)
Particles
(g) (air)
0,144
299,47
2,29
0,3796
0,1456
0,00019
0,006
0,037
59,65
0,513
0,061
0,04
3,6E-05
0,0011
0,04269
68,03
0,585
0,0698
0,0487
4,1E-05
0,0013
0,376
782,3
5,98
0,99
0,380
0,0005
0,0158
0,0104
0,03737
59,653
0,513
0,061
0,04
3,59E-05
0,0011
0,02
0,0029
4,6977
0,0404
0,0048
0,003
2,84E-06
0,0001
0,0016
0,0029
4,698
0,0404
0,0048
0,003
2,8E-06
0,0001
0,0016
215,6
1,6488
0,273
0,0001
0,004
0,001
1,7
0,01
0,1048
0,0017
8
1,0E-06
0,0002
0,39684
0,0034
2,39E-07
0,0002
0,35
0,00299
0,0004
0,0003
6
0,0012
0,0002
8
0,0002
2,0E-07
0,002
4,56
0,03
0,0058
0,0022
2,89E-06
0,0005
0,79
0,0068
0,0008
0,0006
4,78E-07
0,0004
0,696
0,00599
0,0007
0,0005
4,2E-07
215,62
0,0000
3
0,0000
08
0,0000
07
9,2E05
0,0000
2
0,0000
1
0,004
9,1268
0,06979
0,01
0,0044
5,8E-06
0,0002
0,0397
Construction of drainage layer of MSWI BA
Use of diesel by excavator
Production of drainage material from sand (per unit
drainage layer produced with 1 tonne MSWI BA)
0,02
Use of diesel for excavating sand with loading shovel
(Volvo L180E) (includes loading)
0,023
Transport of sand from production site to landfill
(per unit drainage layer that may be produced with 1
tonne MSWI BA) (truck maxload 35 tonnes)
Diesel use, transport of sand
Construction of drainage layer of sand
Use of diesel by excavator
Disposal of one tonne MSWI bottom ash
Diesel use during production of vegetation layer
Use of diesel during construction of vegetation layer
Diesel use for transport of soil for construction of
vegetation layer
Diesel use for construction of surface layer
Diesel use for production of sand for drainage layer
Diesel use for construction of drainage layer
Use of diesel for transport of sand for drainage layer
Use of diesel during production of material to precovering layer
Diesel use for construction of pre-covering layer
0,0286
0,0006
0,0001
0,00012
0,0006
0,00027
0,0002
Transport of sand to landfill for pre-covering layer
0,001
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
SO2 (g)
(air)
Use of NaOH for cleaning of leachate water in 20 years
Use of PIX-111 (iron chloride) for cleaning of leachate
water in 20 years
MSWI BA road
Use of diesel, production of crushed rock
Use of electricity, production of crushed rock
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), alt A
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), alt B
Diesel use, transport of MSWI BA from production site
Use of diesel for construction of sub base layer
Use of diesel for construction of base course layer
CO2 (g)
(air)
NOx (g)
(air)
CH4 (g)
(air)
CO (g)
(air)
HC (g)
(air)
1,09E05
1,5E-06
0
8,3E-08
2,7E-04
N2O
(g)
(air)
4,895
E-06
2,5E07
8,1E-05
0,058
0,00025
3,97E-06
0,002
5,45E-06
4,1E05
1,2E06
2,08E-01
4,3E+02
3,9E+00
4,7E01
2,8E01
0,05
25,97
0,06
1,70E02
1,43E-05
8,8E03
0,0028
7
4,57E04
0,00096
VOC
(g)
(air)
1,2E05
6,5E07
H2S
(g)
(air)
PAH
(g)
(air)
Particles
(g) (air)
6,759E06
4,1E-08
1,6E-01
1,49E-02
237
2,04E-01
0,01
2,4E02
0,0075
0,0005
0,031
49,58
0,43
0,051
0,035
2,99E-05
0,001
1,37
2852,1
21,8
3,6
1,386
0,0018
0,058
0,0889
184,88
1,67
0,199
0,120
0,0001
0,0037
0,036
74,54
0,674
0,08
0,048
4,7E-05
0,0015
0,0666
0,02687
0,7566
1572,98
14,2
1,695
1,023
0,000996
0,03
0,567
0,166
94,375
0,228
0,003
5,3E02
1,1E01
1,09E-04
0,010
1,66E03
3,5E03
8,1E-03
0,017
0,378
Crushed rock road
Use of diesel, production of crushed rock
Use of electricity, production of crushed rock
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), Alt A
Use of diesel for loading crushed rock with loading
shovel (Volvo L180E), Alt B
Transport of crushed rock from production site to road
Use of diesel for road construction
3,9E-02
8,2E+01
7,4E-01
8,3E-02
1,7E+02
1,55
0,05
8,8E02
1,85E01
1,37
2852,1
21,8
3,61
1,386
0,0018
0,0578
0,378
0,13
270,8
2,448
0,29
0,176
0,00017
0,005
0,098
5,2E-05
0,027
0,0017
2,96E-02
6,18E-02
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
A2.2.4 Emissions to water
As (g) (aq)
0,40
0,12
0,20
0,06
0,33
Hg (g) (aq)
0
0
0
0
0
Cd (g)
(aq)
0,128
0,04
0,06
0,02
2,78
Cr (g)
(aq)
1,04
0,476
0,52
0,2379
1,75
Cu (g)
(aq)
141,0
42,50
70,50
21,25
868,8
Ni (g)
(aq)
2,059
0,78
1,0
0,39
55,04
Pb (g)
(aq)
0,523
0,30
0,26
0,15
165,6
Zn (g)
(aq)
3,961
1,782
1,98
0,891
1412,8
Leachate from drainage layer sand, 100 yr (based on L/S 2)
Leachate from drainage layer sand, 100 yr (based on L/S 10)
Leachate from drainage layer sand, 50 yr (based on L/S 2)
Leachate from drainage layer sand, 50 yr (based on L/S 10)
Leachate from drainage layer sand, infinity
0,349
0,349
0,17
0,17
1,54
0
0
0
0
0
0,01
0,01
0,0058
0,0058
0,02
0,23
0,23
0,116
0,116
0,197
0
0
0
0
0,42
0,23
0,23
0,116
0,116
1,097
0,23
0,23
0,116
0,116
0,8
2,3
2,3
1,16
1,16
4,75
Use and maintenance of drainage layer (disposal of ash)
Leachate from drainage layer sand, 100 yr ( based on L/S 2)
Leachate from drainage layer sand, 100 yr ( based on L/S 10)
Leachate from drainage layer sand, 50 yr ( based on L/S 2)
Leachate from drainage layer sand, 50 yr ( based on L/S 10)
0,002
0,0016
0,0006
0,0006
0
0
0
0
6,79E-05
5,43E-05
2,0E-05
2,0E-05
0,001
0,001
0,0004
0,0004
0
0
0
0
0,001
0,001
0,0004
0,0004
0,001
0,001
0,0004
0,0004
0,01
0,01
0,004
0,004
Use and maintenance of pre-covering layer
Leachate from pre-covering layer, 100 yr (based on L/S 2)
Leachate from pre-covering layer sand, 100 yr ( based on L/S 10)
Leachate from pre-covering layer sand, 50 yr ( based on L/S 2)
Leachate from pre-covering layer sand, 50 yr ( based on L/S 10)
Leachate from pre-covering layer sand, infinity
0,0004
0,0004
0,0002
0,0002
0,01797
0
0
0
0
0
1,3E-05
1,3E-05
0,000005
0,000005
0,000267
0,000267
0,000267
0,0001
0,0001
0,002
0
0
0
0
0,004907
0,000267
0,000267
0,0001
0,0001
0,01
0,00027
0,00027
0,0001
0,0001
0,00987
0,0027
0,0027
0,001
0,001
0,055
Use and maintenance of the landfill
Leachate from MSWI BA in landfill,100yr (based on L/S2)
Leachate from MSWI BA in landfill, 100 yr (based on L/S 10)
Leachate from MSWI BA in landfill, 50 yr (based on L/S 2)
0,00046
0,00046
0,00017
0
0
0
0,0001
0,0001
0,000055
0,001
0,001
0,0004
0,16
0,16
0,06
0,002
0,002
0,000885
0,00454
0,00454
0,0017
Leachate from MSWI BA in landfill, 50 yr (based on L/S 10)
Leachate from MSWI BA in landfill, infinity
5,45E-05
0,4
0
0
0,000018
3,48
0,000205
2,19
0,018267
1086
0,0003
68,8
0,0006
0,0006
0,0002
0,000130
5
207
0,000766
1766
Use and maintenance of MSWI BA road
Leachate from sub base with MSWI ash, 100yr ( based on L/S 2)
Leachate from sub base with MSWI ash, 100yr ( based on L/S 10)
Leachate from sub base with MSWI ash, 50yr ( based on L/S 2)
Leachate from sub base with MSWI ash, 50yr ( based on L/S 10)
Leachate from sub base with MSWI ash, infinity
Leachate from base course with crushed rock, 100 yr ( based on L/S 2)
0,005568
0,001759
0,002784
0,000879
0,33408
6,27E-03
0
0
0
0
0
0,00E+00
0,001774
0,000581
0,000887
0,00029
2,784
1,94E-04
0,014435
0,006597
0,007218
0,003298
1,752
8,06E-04
1,954758
0,589258
0,977379
0,294629
868,8
8,90E-03
0,028548
0,010823
0,014274
0,005411
55,04
4,37E-03
0,007258
0,0042
0,0036
0,0021
165,6
5,08E-04
0,054919
0,0247
0,027
0,01235
1412,8
5,24E-03
Use and maintenance of drainage layer of MSWI BA
Leachate from drainage layer MSWI BA, 100 yr (based on L/S 2)
Leachate from drainage layer MSWI BA, 100yr (based on L/S 10)
Leachate from drainage layer MSWI BA, 50yr (based on L/S 2)
Leachate from drainage layer MSWI BA, 50 yr (based on L/S 10)
Leachate from drainage layer MSWI BA, infinity
Use and maintenance of drainage layer of sand
Leachate from drainage layer sand, infinity
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
As (g) (aq)
Leachate from base course with crushed rock, 50 yr ( based on L/S 2)
Leachate from base course with crushed rock, infinity
Use and maintenance of crushed rock road
Leachate from sub base and base course with crushed rock, 100 yr
(based on L/S 2)
Leachate from sub base and base course with crushed rock, 50 yr
(based on L/S 2)
Leachate from sub base and base course with crushed rock, infinity
Hg (g) (aq)
3,14E-03
6,13E-02
0,00E+00
0,00E+00
Cd (g)
(aq)
9,68E-05
1,29E-02
Cr (g)
(aq)
4,03E-04
9,35E-02
Cu (g)
(aq)
4,45E-03
5,16E-02
Ni (g)
(aq)
2,19E-03
4,84E-01
Pb (g)
(aq)
2,54E-04
1,13E-01
Zn (g)
(aq)
2,62E-03
9,03E-01
0,02
0
0,0007
0,002
0,03
0,01588
0,0018
0,0190
0,011
0,22
0
0
0,00035
0,04688
0,001
0,33989
0,016
0,1875
0,0079
1,758
0,00092
0,4102
0,0095
3,2817
A2.3 Reference - appendix 2
Literature
Almemark, M, Carlsson, AS, Palm, A. (2003) Jämförande miljöbedömning av tre fällningskemikalier PIX-111, PIX-110 och PIX-118. Swedish Environmental Research
Institute (IVL), (In Swedish).
Gustafsson, M., von Bahr, B., Carlson-Ekvall, A., Johansson, P., Reuterhage, Å., Wallman, S. (2003) Inledande laboratorieförsök, projekt AIS32, delrapport 1. Swedish
Agency for Innovation Systems (Vinnova), Göteborg.
Mroueh, U., Eskola, P., Laine-Ylijoki, J., (2001): Life-cycle impacts of the use of industrial by-products in road and earth construction. Waste Management 21, 271-277.
Olsson, S., Kärrman, E., Gustafsson, J.P. (2004) Environmental systems analysis
of the use of bottom ash from incineration of municipal waste for road construction. Proceedings of the 19th International Conference on Solid Waste Technology and
Management, March 21-24, 2004, Philadelphia, PA USA.
RVF (The Swedish Association of Waste Management). (2002) Kvalitetssäkring av slaggrus från förbränning av avfall. RVF 02:10, (In Swedish).
SGU (Geological Survey of Sweden). (2003) Aggregates –production and resources 2002. SGU 2003:4, Uppsala, (In Swedish, with an English summary).
Stripple, H. (2001) Livscykelanalys av väg - En modellstudie för inventering. Swedish Environmental Research Institute (IVL), Göteborg, (In Swedish with an English
summary).
Svingby, M., Båtelsson, O. (1999) LCA av lättfyllnadsmaterial för vägbankar. National Road Administration, Vägverket1999:67, Borlänge, (In Swedish).
Tossavainen, M., Håkansson, K. (1999) Reference data of leaching of natural materials and effects on its leaching properties of ageing. Swedish Environmental Protection
Agency, 1999: AFR-Report 254. Stockholm.
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 2
Uppsala Kommun VA-och Avfallskontoret. (2004) Miljörapport 2003 – Hovgårdens avfallsanläggning. Uppsala ( In Swedish)
Wallén, E. (1999) Livscykelanalys av dricksvatten – en studie av ett vattenverk i Göteborg. Degree thesis, Chalmers University of Technology, Göteborg, (In Swedish).
Internet
Naue Fasertechnik GmbH &Co. KG. (2003) Fibre-reinforced geosynthetic clay liner.Available:www.naue.com [ 2004, September 18]
Naue Fasertechnik GmbH &Co. KG. (2004) Geotextiles for road construction Secutex GRK. Available: www.naue.com [2004, September 18]
ViaMichelin. (No date): Route planner. Available: www.viamichelin.com
Environmental Systems Analysis for utilisation of bottom ash in ground constructions
Appendix 3
Appendix 3
A3.1 Difference in substance flow when certain life cycle stages are excluded
Table: Difference in substance flow when certain life cycle stages are excluded.
Substance flow
Scenario 3 Scenario 3
Drainage
Drainage
without
with barrier layer of
layer of
barrier
layer
MSWI BA
MSWI BA
layer
without
with
machineries machineries
Resource use 1
Energy [MJ]
138
138
147
148
Sand [tonnes]
0,93
0,93
0
0
Crushed rock [tonnes]
1,17
1,17
0
0
Waste [g]
1,74
1,74
0,50
0,50
Emissions to air 2
SO2 [g]
3,0
3,1
3,3
3,9
NOx [g]
48
49
51
52
CO [g]
7,2
7,2
8,5
8,6
CO2 [g]
6030
6050
6729
6924
CH4 [g]
0,007
0,007
0,005
0,8
VOC [g]
0,027
0,027
0,0079
0,11
(VOC+NMVOC)
HC [g]
3,2
3,3
3,3
3,3
N2O [g]
0,13
0,13
0,14
0,14
Particles [g]
1,3
1,3
0,9
4,4
Emissions to water 3
COD [g]
0,09
0,09
0,10
0,10
Ntot [g]
0,014
0,014
0,016
0,017
Oil [g]
0,03
0,03
0,03
0,03
Phenol [g]
0,04
0,04
0,05
0,05
As [g]
0,3
0,3
0,13
0,13
Cd [g]
0,01
0,01
0,04
0,04
Cr [g]
0,19
0,19
0,48
0,48
Cu [g]
0,23
0,23
42,5
42,5
Ni [g]
0,2
0,2
0,78
0,78
Pb [g]
0,19
0,19
0,30
0,30
Zn [g]
1,90
1,90
1,78
1,78
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