Incineration Or Recycling Of Waste In Stockholm Environmental Sciences Essay

The amount of waste has increased every year in line with economic growth in the society and so progressively becoming a bigger concern. The issue of increasing waste in the society needs to be considered carefully and strategies for building sustainable solutions must be incorporated into the daily agenda for companies as well as for households. Decisions regarding large investments in our society, like different ways of handling waste, are complex and require a systematic approach supported with appropriate decision methods and models.

The overall aim for this study is to investigate how incineration and recycling in Stockholm municipality is organized and also to evaluate both the costs and the benefits using CBA model. Which method is the best when both considering financial and environmental aspects?

The results from the Cost Benefit Analysis shows clearly that incineration has a large advantage relative recycling in matter of financial benefits. This benefit comes mainly from the fact that it is possible in Sweden and at the Högdalenverken to produce district heating and electricity from the incineration of MSW. This energy recovery is not just good from an environmental point of view but also from a financial. Another important result is that the flue gas treatment in Sweden and Högdalenverken is very effective due to use of modern technologies. The cleaning process with use of filters, scrubbers and catalysts are very effective and has a large impact on the emissions released to the environment. When analyzing the full picture with incineration compared to recycling it is clear that in Stockholm is the benefits larger for incineration as a large scale profitable treatment method for the municipal solid waste (MSW).

Introduction

In the early 1800s the main occupation in Sweden was agriculture and the most important processes linked to farming was sowing, harvesting and managing animals. During this period it was quite clear for the farmers what the input and output of their processes were and it was probably not that hard to control these processes and the local environmental impact. The main issue was the weather and the main resource was manpower. The dawn of industrial technology brought the industrial revolution. It became clear that new companies and households were not only impacting the local environment but also much larger areas via waterways and air streams. The amount of waste has, in general, increased every year in line with economic growth and so progressively becoming a bigger issue for our society. The issue of increasing waste in the society needs to be considered carefully and strategies for building sustainable solutions must be incorporated into the daily agenda for companies as well as for households. Decisions regarding large investments in our society, like different ways of handling waste, are complex and require a systematic approach supported with appropriate decision methods and models.

Aims and Objectives

To be able to fulfill the overall aim a number of objectives has been established;

Describe the concept of Ecological Economics and its context.

Describe and explain how Cost Benefit Analysis can be used to evaluate waste handling.

Describe what kind of waste that is incinerated and recycled in Stockholm municipality.

Describe and analyze how incineration of waste is managed in Stockholm municipality.

Describe and analyze how recycling of waste is managed in Stockholm municipality.

Calculate and evaluate costs and benefits for both waste incineration and recycling.

System Boundary

One geographical boundary is that this study will take place in Stockholm municipality but when suitable information is missing in Stockholm there is a need to broaden this boundary.

It is also stated that there is two options of waste handling that will be studied in this report, incineration and recycling. Still these methods need to be put into its context.

Methodology

The information used in this report comes mainly from course literature used in the course Ecological Economics (MJ2694) at KTH. Other sources of information are internet and databases with articles for the specific research area.

Theoretical Framework

This chapter will introduce the research area as well as build the basis for good understanding of how waste management is handled in Stockholm municipality. This study is focused on using Cost Benefit Analysis as method for analyzing the two options incineration and recycling.

Ecological Economics Perspective

Ecological Economics (EE) was founded at the end of 1980s and this field is often categorized in multi-discipline or trans-discipline research depending on the views of different scholars (Constanza, Daly and Bartholomew, 1991; Daly, 2004). This section will briefly address the concept and the terms of EE that will be used in this study. Due to the multi-disciplinary nature of EE, it seems important to define the basic idea of Ecological Economics before addressing the waste management methods from an ecological economics perspective.

The basic idea of Ecological Economics

In a broader sense this field of study investigates the relationship between ecosystems and economic systems (Constanza, Daly and Bartholomew, 1991). However, as Bergh (2001) discusses in relation with the core of EE, the combination of the two different fields of study was enabled based on the view that the economy is a subsystem of a larger local and global ecosystem, and this relationship provides the reason to set limits to the physical growth of the economy. At this point it is differed from mainstream economy which has the focus on market mechanism without consideration of actual human and ecosystem behavior. Ecological Economics responds to failure of mainstream economics to build a bridge between the gap of natural science and economics (Gowdy, 2000). Economic scientist aspires to find simple and general laws that cover all possible economic situations. The focus on markets in economy, with ignorance of the constraints imposed by environment and the human behavior, has concluded in a variety of environmental degradation (Gowdy, 2000).

An important distinction of sustainability in EE is concerned with the differences between development and growth. Development refers to an increase in the quality of output without an increase in mass and energy usage, whereas growth refers to quantitative increase in economic output (Gowdy, 2000). Development with an increase of quality of output also considers equal allocating resources significant and efficiency of distributing resources (Daly and Farley, 2004).

Cost Benefit Analysis

One of the methods used for decision-making is Cost Benefit Analysis (CBA) and with this method it is possible to evaluate the expected costs of an investment against the expected benefits to determine the most profitable alternative. In terms of goal setting or making a decision, CBA is a support for the decision makers. It is a rather simple method that is widely used for many years. (Entrepreneur, 2010)

To illustrate how simple the CBA could be is to put a piece of paper where a line divides it into two parts. In the left side costs are stated and in the right side the potential benefits are described. Both the costs and benefits should be stated to reach a specific goal. After writing the different costs and benefits they need to be added up to be able to compare the both sides and to see which the largest part is. As this is a very simple method for decision-making it could be used for a first screening the situation but probably a more sophisticated method will be needed for deeper analysis. (Entrepreneur, 2010)

One example when a CBA is used could be when a Sales Director of a company needs to take a decision if the company should invest in a new efficient contract and sales processing computer based system. At present time has the sales department just a few computers and this kind of investment would require quite much employee training. There is a risk that there will be a decrease in sales during the implementation period of this new computer based system. The total costs are estimated to about $55,800 (computers, installation and training). The potential benefits are linked to the estimated increase in sales capacity and better customer service performance which is approximately $90,000 annually. With this costs and benefit figures is it possible to calculate the profit of the investment as well as the return of investment of about eight months. (Entrepreneur, 2010)

Incineration in Stockholm Municipality

There are many ways of taking care of waste and incineration if one of the most important treatment methods. According to the waste hierarchy is incineration in the middle of the waste hierarchy. The order is from the top of the waste hierarchy; waste reduction/prevention, re-use, recycling & composting, incineration and landfill (Williams, 2005).

In Stockholm is incineration is one of the main ways of waste treatment. For Stockholm is Högdalenverket the main facility for incineration of waste. At this plant is heat and electricity produced from mainly combustion of municipal solid waste (MSW) as well as industrial waste. This facility consists of six different burners to produce the heat and electricity. One important change in the district heating net of Stockholm was made in 2008 when the southern and central district heating net was merged into one net. Högdalenverket is the major producing unit of district heating in Stockholm. In Högdalenverket is the different shares of waste; MSW from Stockholm 235,432 ton, MSW from surrounding municipalities 158,001 ton and industrial waste 90,917 ton. The part of the MSW that comes from Stockholm is 235,432/484,450 = 0.49, that is 49% of the total treated waste in Högdalenverket. There are also needed different fuels to be able to run the plant, for example burning oils and bio oils (Fortum, 2010).

In Table 9 in Appendix B, it is obvious that waste from food is totally dominating the MSW with about 38.9% of the total amount. The second biggest part is board and corrugated cardboard with 9.3% and the third biggest is newspapers with 7.2%. These three parts makes about 55% of the total MSW in Stockholm and needs to be treated accordingly. The figures shown in Table 9 come from an analysis called “plockanalys” (eng. pick analysis). This means that MSW in Stockholm has been analyzed by looking into garbage bags from citizen’s in the municipality.

A typical modern waste incinerator plant is divided into five different process steps according to Williams (2005). The first step is the waste delivery and the final district heating or electricity generation. The steps are described below also see Figure 1 for an illustration:

I) Waste delivery, bunker and feeding system – this stage comprises the arrival of waste to the incineration plant, its storage in the bunker for further utilization and the continuous feeding to the furnace.

II) Furnace – it is here where the incineration of the waste occurs. It can be divided in three phases; drying and devolatilisation, combustion of volatiles and soot and combustion of the solid carbonaceous residues.

III) Heat recovery – due to the high temperature of the flue gases, around 750 – 1000 °C, it is necessary to cool down the gases before passing through the cleaning system. During this process, by the utilization of a boiler, the heat of the flue gases is transferred to water therefore producing steam.

IV) Emissions control – this stage comprises all the measures and techniques utilized to treat the flue gases in order to comply with the European Commission Waste Incineration Directive (2000), which regulates all the emissions resultant from incineration plants.

V) Energy recovery via district heating or electricity generation – through the utilization of turbines or heat exchangers it is possible to use the steam produced in the heat recovery phase to generate electricity or district heating.

Figure 1 Typical layout of a MSW incineration plant (EC, 2006)

Recycling in Stockholm Municipality

Waste recycling can be considered as a favored way for material and energy recovery. Reasonable sorting system is the most kernel part in material recycling. The main aims of waste recycling is to separately store recyclable material for reuse and ensure that waste which can be processed for recovery of material and energy. It is also to separately store hazardous material for disposal in landfills or through appropriate processing and also to minimize the waste and ensure reduction in landfill space for final disposal. (Barker and Zabinsky, 2010) The general idea of waste recycling in western countries, is based on first household sorting and recycling and secondly process in recycling center.

Household Sorting and Recycling

The idea of household recycling adopts the method of waste sorting in households. There are different kinds of waste that is recycled for example packaging, food, paper, metal and glass waste. These are collected via waste bins located at households, business facilities, at hotel and other public areas. The collected waste will be transported for recycling or for downgraded recovery. The household waste sorting starts normally in the kitchen where food waste and other mixed waste are sorted into their own separate waste collection bins. The waste contains recyclable materials such as glass, metal and paper that are sorted in their separate bins. The waste also contains hazardous material which can be dangerous or harmful to human health or the surrounding environment and should not be mixed with other waste. The hazardous waste must be kept separately and taken to specific recycle stations.

In 1994 was the legislation passed, that requiring households to sort waste into separate streams to facilitate collection under the EPR legislation. Since the Swedish system relied on bring systems it is not really compulsory. Sorting waste by the households is regulated but not enforced. In almost all municipalities in Sweden, there are different kinds of waste bins used to collect different kinds of household waste separately. The method of classifying different household waste follow these different groups; paper & board, plastic, glass, metals, food and other (e.g. batteries, lamps). For the different kind of waste mentioned, there are the corresponding bins to collect them. (Paxéus, 1999)

Swedish cleaning company jointly is formed by non-governmental organizations. Companies in some cities in Sweden provides each household with free garbage bags which is used to keep waste paper, scrap metal, waste glass bottle and waste fiber separately. The special truck always collects recyclable periodically, while the other garbage collection once a week. In addition, in apartments, hotels and other public residential area also has the special collection devices used to keep various types of waste for recycling. (Green Alliance, 2009)

The reusable bottles in Sweden, such as plastic bottles and metal cans, could be collected at supermarkets which have self-service recycle machines. People can get money back once by applying the used bottles into the self-service machine which is designed as a deposit refund system. About 9,000 tons of recycled in Sweden for cans and about 2 million tons of glass bottles are collected every year. 75 million tons of paper are recovered per year of which 240,000 tons is collected from households. (Docstoc, 2009)

Process in Recycling Center

Recycling Centers manage the collected waste from all scattered areas. The recycling begins with material collection and separation, followed by sorting at a Materials Recovery Facility (MRF), which is also known as recycling centers and after that further reprocessing or reuse. The recycling center can be defined as a demarcated system where people bring and sort their large-sized, hazardous and electrical waste. This is including refrigerators, furniture, electronics, garden waste, solvents and paints. The waste is sorted and placed in large containers, cages and boxes. However, kitchen waste is not accepted at these recycling centers. (Krook and Eklund, 2010) In contrast to waste separation in source site, waste materials and recyclables sorted in recycling centre can be thought of solution at the end of the waste stream.

A typical materials recovery centre comprises of several buildings including receiving and processing waste from the producers or storing a short period inventory of conditioned waste as a warehouse. All the buildings are necessarily equipped with appropriate facilities for treating and conditioning the waste. The standardization of the recycling centre strictly follows reference design certified by relevant agencies in order to achieve cost effective performance. Figure 2 below shows the recycling centre which can handle with a mixture of containers composed of crystal or colored glass, ferrous metals, aluminum tins and paper cartons. The procedure is similar to un-segregated MSW recycling facility. Pre-segregation occurs before waste is transmitted to the facility which indicates a higher recovery rate involved (Williams, 2005).

Figure 2. Materials Recycling Facility. (Warmer Bulletin 59, 1998. Reproduced by permission of R.C. Strange)

Materials recycling facilities handles the segregated material streams with a range from 3 to 8 waste components, of particular materials which may be separated or mixed. By doing in this way, it will lower the contamination degree while increase the recycling rates. The separation processes are generally classified into mechanical and manual separated operations. Many types of materials like corrugated cardboard which is already through the pre-segregating procedure will be delivered into the baler directly at the initial input stage. The stages of separation include trommel screening, magnetic separation, and manual sorting. Although mechanical separation processes are in wider applications, yet manual sorting procedure is still considered as a favored way to detach different waste especially like colored glasses or plastics. (Williams, 2005)

Results

In this section will the result from data and literature research be presented. To be able to illustrate the result in an easy and logical way, will first the cost and benefits for incineration be shown and after that the cost and benefits for recycling in Stockholm. The final result from the full cost benefit calculation will be illustrated in a table.

Costs for Incineration in Stockholm Municipality

The costs for incineration are assumed to be the costs for collection and transport of the household waste and the full cost for the incineration plant.

Costs for Collection and Transportation

About 35 employees are working in the waste management office in Stockholm municipality. Total population in Stockholm for 2009 is 829,417 according to the annual report of Stockholm municipality (Stockholms Stad, 2010). Weighed household waste at Högdalenverken is 130 kr * 829,417 = 107,824,210 kr per year. The cost for collection, transport and removal of household waste is about 520 kr per person and year in Stockholm municipality according to annual report.

Total costs for collection, transport and removal of household waste is equal to 520 kr * 829,417 = 431,296,840 kr/year

Costs for Incineration Plant

Högdalenverket has an annual capacity of treating about 700,000 ton waste and the share of MSW from Stockholm Municipality is 235,432 ton per year. In the study made by the Swedish Environmental Research Institute (IVL, 1999) is the total cost for an incineration plant about 400 kr per ton. This information is to be found in table A6 in the IVL report from 1999.

Cost Assumptions for Incineration Plants (IVL, 1999):

Investment, Capacity0.68 * 145,000

Depreciation time = 20 years

Power (MW), Capacity * 0.38 * 10-3

Employees, 10+(14.3*Power+200)0.5

Maintenance and operational costs, 2.5% of the investment

Chemicals and lime, 20 kr/ton waste

Capacity = plant capacity (ton/year)

Interest rate = 5%

With a total amount of waste that is 235,432 ton/year and a cost of about 400 kr/ton waste treated will the total cost per year be 400 kr/ton * 235,432 ton/year = 94,172,800 kr/year.

The total cost for incineration according to the above calculations is a combination of costs for collection and transportation as well as costs for the incineration plant. Probably is it also some minor cost for handling the residues from the incineration but this cost was not possible to find.

Total cost for incineration is 431,296,840 kr/year + 94,172,800 kr/year = 525,469,640 kr/year.

Benefits for Incineration in Stockholm Municipality

In Stockholm are approximately 130,000 households using the district heating from Högdalenverken and this district heating is generated from incineration of MSW (Fortum, 2009). The annual cost for every household is estimated to be about 18,960 kr/year. This is based on an annual energy usage of 21,000 kWh (Fortum, 2010a).

The total cost for households (equals to benefits from district heating) will be 130,000 * 18,960 kr/year = 2,464,800,000 kr/year and this is the major part of the benefits from incineration.

The other part is the electricity produced. According to Fortum homepage (Fortum, 2010) is the power output from the plant 71 MW. There are two steam turbines with a power output of 27 MW and 44MW which gives a total of 71 MW. The calculation to convert it into kW is 71 MW * 1000 = 71,000 kW. The calculation of the produced electricity per year for Högdalenverken is 71,000 kW * 24 hours/days * 365 days/year = 621,960,000 kWh/year.

The assumed price for electricity is collected at Fortum homepage (Fortum, 2010b) and the page “Historiska elpriser”. To calculate the total income from electricity we have used the average monthly electricity price from January 2009 to December 2009 and this is 44.815 öre/kWh = 0.44815 kr/kWh. This average price is then multiplied with the total electricity produced for 2009 which gives 621,960,000 kWh/year * 0.44815 kr/kWh = 278,731,374 kr/year.

The benefits from incineration is a combination of district heating and electricity produced in Högdalenverket. Still is the part of waste coming from Stockholm municipality about 49% of the total production in Högdalenverket which gives; 0.49 * (2,464,800,000 kr/year + 278,731,374 kr/year) = 1,344,330,373 kr/year.

Costs for Recycling in Stockholm Municipality

The part of material recycling which includes packaging, electronic waste, as well as bulky waste collected as metal fraction in municipal recycling centers in Sweden was 1,586,600 ton for 2009, 169.9 kg per person and corresponds to 35.4 % of all treated household waste. Therefore the total amount of recycling in Stockholm is 169.9 kg/person * 829,417 persons = 140,918 ton/year. This was calculated based on population size, see Table 1below.

Table 1 The Amount of Recycling per Year in Stockholm (Avfall Sverige, 2010)

Sweden

Stockholm

Material recycling

1,586,600 ton

140,918 ton

Material recycling per person

169.9 kg

–

Population

9,354,462

829,417

The cost for waste management is in average 690 kr/person per year. It is possible to assume that the cost for recycling is 244 kr/person per year based on the charge of recycling 35.4% of total waste. The cost of recycling is 244 kr/person * 829,417 = 202,377,748 kr/year, see Table 2.

Table 2 The Cost of Recycling per Year in Stockholm (Avfall Sverige, 2010)

1 person/year

Per year

Cost for waste management

690 kr

–

Cost for recycling

244 kr

202,377,748 kr

Rate of recycling of total waste

35.4%

Benefits for Recycling in Stockholm Municipality

The vast majority of recycling materials in Stockholm is generally categorized into 5 groups; plastic, metal, paper, e-waste and glass. In the Swedish Waste Management report for 2010 (Avfall Sverige, 2010) is the explicit recycling data display as a Table 3 below.

Table 3. Recycling Material Detail in Sweden 2009 (Avfall Sverige, 2010)

Waste Type

[ton]

[kg/person]

Recovery degree [%]

Parliament recycling target [%]

Newspaper & Paper Package

899,000

96.4

Office Paper

118,000

12.6

Plastic

44,430

4.8

Glass

177,300

19.0

Metal & Metal Package

203.320

21.8

E-waste

143.850

15.4

According to municipal demographic statistic in 2009, the municipality of Stockholm holds a population of 829,417. Therefore, the waste statistic in Stockholm is as demonstrated in Table 4. One example of calculation is for Newspaper & Paper Package where the kg/person is 96.4 and this times 829,417 equals 79,955,799 kg for a year.

Table 4. Recycling Material Amount in Municipality of Stockholm 2009

Waste Type

Waste Amount [kg]

Waste Amount [ton]

Newspaper & Paper Package

79,955,799

79,956

Office Paper

10,450,654

10,451

Plastic

22,394,259

22,394

Glass

74,647,530

74,648

Metal & Metal Package

18,081,291

18,081

E-waste

12,773,022

12,773

On basis of reports regarding cost benefit of waste recycling as well as statistics and some assumptions, economical market value for these recycling materials are calculated, see Table 5.

Table 5 Value of Recovered Materials

Waste Type

$ per ton

Newspaper &Paper Pack

90 [1]

Office Paper

2571

Plastic

6501

Glass

751

Metal & Metal Package

1,200 [2]

E-waste

1,890 [3]

The calculation of total benefits is a combination of waste amount value from Table 4 and $ per ton value from Table 5. This gives 79,956*90 + 10,451*257 + 22,394*650 + 74,648*75 + 18,081*1,200 + 12,773*1,890 = 7,196,040 + 2,685,907 + 14,566,100 + 5,598,600 + 21,697,200 + 24,140,970 = 75,884,817 USD.

The average USD rate vs. SEK is 7.63 [4] for 2009 and this gives a total benefits for recycling of 75,884,817 USD * 7.63 = 579,001,154 kr/year.

Cost Benefit Analysis of Incineration vs. Recycling

The total cost and benefits from calculations in the results chapter is illustrated in Table 6 below. It is clear that the financial profit from incineration is best compared to recycling in Stockholm municipality. The table also shows that the driver behind this result is the benefits generated by district heating from incineration. One important point to mention is that the total amount of waste for incineration is 235,432 ton/year and for recycling 140,918 ton/year.

Table 6 Calculation of Cost and Benefits for Incineration and Recycling

[kr/year]

Incineration

Recycling

Benefits

1,344,330,373

579,001,154

Costs

– 525,469,640

– 202,377,748

Profit

818,860,733 [kr/year]

376,623,406 [kr/year]

Extended Cost Benefit Analysis

Environmental Impact from Incineration

In spite of being an attractive technological option for waste management, incineration of MSW is the subject of debate around the world. Though incineration of MSW contribute to energy recovery through district heating and electricity, but in absence of efficient controls, pollutants may be discharged into air, land and water which may influence human health and environment.

There are different ways of treating flue gases during the incineration process. Cyclones may be seen as an improved version of settling chamber. Their specific geometry increases particles speed as well as the probability they hit the cyclone walls. They can then fall down and being collected. Often used in parallel and it is then called multi-cyclones. Cyclones present several advantages as pre-treatment methods. Another alternative which can be combined with cyclone as pre-treatment is the use of electrostatic precipitator. These expensive pieces of equipment are able to handle high temperature and may be a good ally of cyclones because of their high cleaning efficiency including very small particles. The removal of gaseous compounds such as acidic gases or nitrites requires the use of additional reagent such as activated carbon or limestone. Their prominence is mainly due to their low investment cost and implementation flexibility. They can indeed deal with various flow characteristics, including very wet and hot gases. Wet scrubbers are not without drawbacks (Persson, 2006).

Environmental Impact from Recycling

In general recycling is widely assumed to have a lower impact than producing new product from raw materials for all the waste items, see Table 7.

Table 7. Impact of Recycling (Parliamentary Office of Science and Technology, 2005)

Material

% of Household Waste

Energy

Emissions

Raw Material Saved per Ton Recycled

Paper

28-70%

95% less (air

pollutants)

———

Glass

18% less

30% less

1.2

Plastic

up to 66%

less

—-

1.8

Cans (Fe)

70% less

86% less

2.0

Can (Al)

95% less

4.0

Based on Rebel recycling program between 2003 and 2008, it is possible to calculate the following positive impact on the global environment from recycling in Stockholm, see Table 8.

Table 8. Positive Impact of Recycling in Stockholm (University of Nevada, 2008)

1 ton

140,918 ton/year

Tree Saved

17 forty foot Douglas fir trees

2,395,606 forty foot Douglas fir trees

Water Saved

7,000 gallons of water

9,86426 gallons of water

Air Pollution Prevented

60 pounds of air pollutants

8,455,08 pounds of air pollutants

Landfill Space Saved

3 cubic yards of landfill space

422,754 cubic yards of landfill space

Energy Saved

4,102 kWh of electricity

578,045,636 kWh of electricity

There are some negative effects for the environment with recycling and they mostly caused by the process of recycling treatment. Some negative impacts are abandoned dump sites that can damage the surrounding environment. It can cause significant risk of harmful chemicals in the trash which can be mixed in the water and soil. Also is there a risk if toxic material reaches soil or rainwater that produces significant pollution. Furthermore is it worthy to mention that there are limits of recycle materials. Paper recycling can be less beneficial compared to manufacturing because additional industrial processes such as bleaching, are required to make the paper reusable. The process of recycling papers has negative environmental impact and can cause health problems. Plastics is not an useful material to recycle since there is difficulties either on systematic sorting different kind of plastic or manufacturing with combining different kind of plastic. (Buzzle.com, 2010)

According to Finnveden and Ekvall (1998) research on Life Cycle Assessment (LCA), the overall preference of one choice over another cannot be drawn with positive and negative environmental impact. However, the interesting note is that the more fossil fuel is used the more is recycling probably a preferable choice. Also when considering the increasing use of plastics relative the use of paper with regard to CO2 emissions to the air, the benefits from recycling instead of incineration will probably be larger.

Discussion

Still are both the economic and environmental benefits of incineration heavily dependent on the incineration technology in Högdalenverken. The content in the municipal waste is also of great importance when it comes to generation of flue gases. Normally has MSW a rather stabile content which is good for the combustion process. Several factors are important; the calorific value that decides the energy amount in the waste. Also is the moister content critical as it needs to be at decent level to make ignition easy and the volatile content in the waste. The ash content is of great importance as it is a heterogeneous and contains non-combusted material. A risk is if the MSW contains too much heavy metal that is hazardous and linked to health risks.

To be able to minimize the flue gas emissions from MSW incineration, it is important with optimal conditions in the combustion chamber. Factors as temperature, time and turbulence (3T-Rule) are critical as well as level of oxygen. It is a must to reach complete combustion and burn-out of volatile hydrocarbons in the chamber. With suitable conditions in the chamber will it be possible to control the emissions of NOx, VOC as well as dust and metal particles to some extent. Also is high temperature in the furnace important to make it possible to decrease levels of dioxins and furans.

Another factor that is having an impact of the cleaning results of the flue gases is the amount of investment capital available at the proper time. With a solid financial situation will it be possible to invest in modern technologies that have higher cleaning results but on the other hand are regulations and laws a driving factor for improving the environmental work in many organizations today.

One parameter that is of importance in the choice between incineration and recycling is the level of fossil fuel used in the society. When it is a higher usage of fossil fuel in the incineration process, it will be better with recycling compared to incineration. Today there are a decent level of fossil fuel usage in Stockholm and at the Högdalenverken and this is in favors for incineration.

Conclusions

The most obvious conclusion from this study is that incineration has a clear financial competitive advantage relative recycling of materials in Stockholm municipality. This is mainly due to the fact that incineration incorporates extensively energy recovery through district heating and also electricity production when burning waste through modern incineration technologies.

Another important conclusion is that the flue gas treatment in Sweden and Högdalenverken is very effective due to use of modern technologies. The cleaning process with use of filters, scrubbers and catalysts are very effective and has a large impact on the emissions released to the environment. When analyzing the full picture with incineration compared to recycling it is clear that in Stockholm is the benefits larger for incineration as a large scale profitable treatment method for MSW.

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