Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories

E M I SS IONS FR OM WAS T E
INCIN ERATIONACKNOWLEDGEMENTS
This paper was written by Mr. Bernt Johnke (Germany) and reviewed by Robert Hoppaus (IPCC/OECD/IEA),
Eugene Lee (US), Bill Irving (USEPA), T. Martinsen (IPCC/OECD/IEA), and K. Mareckova (IPCC/OECD/IEA).

ABSTRACTThe incineration of municipal waste involves the generation of climate-relevant emissions. These are mainly
emissions of CO2 (carbon dioxide) as well as N2O (nitrous oxide), NOx ( oxides of nitrogen) NH3 (ammonia) andorganic C, measured as total carbon. CH4 (methane) is not generated in waste incineration during normal operation. It
only arises in particular, exceptional, cases and to a small extent (from waste remaining in the waste bunker), so thatin quantitative terms CH4 is not to be regarded as climate-relevant. CO2 constitutes the chief climate-relevant
emission of waste incineration and is considerably higher, by not less than 102, than the other emissions.
Formulas (1) and (2) are to be used for the purpose of compiling an inventory of greenhouse gas emissions, taking
the following into account:
The incineration of 1 Mg of municipal waste in MSW incinerators is associated with the production/release ofabout 0.7 to 1.2 Mg of carbon dioxide (CO2 output). The proportion of carbon of biogenic origin is usually in therange of 33 to 50 percent. The climate-relevant CO2 emissions from waste incineration are determined by the
proportion of waste whose carbon compounds are assumed to be of fossil origin. The allocation to fossil orbiogenic carbon has a crucial influence on the calculated amounts of climate-relevant CO2 emissions.
Annex 1 contains a description of a method to calculate the energy credit for the use of waste as a substitute forfossil fuel (MSW incineration plants with energy recovery). Formulas (3) and (4) are to be used for the purpose of
a comparative evaluation of the climate-relevant emissions from waste incineration in relation to those of othertypes of energy production. A factor that has a decisive influence on the calculated amounts of climate-relevant
emissions from waste incineration plants with energy utilisation is the credit allowed or allowable due to thesubstitution of energy from fossil fuels. The latter in turn is influenced by the energy carriers used as a basis tocalculate the emission factor of the power plant mix.
An energy transformation efficiency equal to or greater than about 25 percent results in an allowable average
substituted net energy potential that renders the emission of waste incineration plants (calculated as CO2
equivalents) climate-neutral due to the emission credits from the power plant mix.

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Background Paper

1

NATURE, MAGNITUDE AND DISTRIBUTION
OF SOURCE

1.1

Waste incineration

The role of waste incineration differs in the countries of the world. While in the industrialised countries in Europe aswell as in Japan, the USA and Canada the proportion of waste burned in waste incineration plants can be very high(up to 100 percent), in most developing countries landfilling is the more common waste management practice.

1.1.1

Status of waste incineration in the various EU member
states

The role of municipal waste incineration in European countries varies from country to country. The compilation
presented below (Table 1) shows the amounts of municipal waste incinerated in waste incineration plants ofcountries in western Europe. It has been taken from an EU report on waste incineration which has been prepared
for the European Commission by the Netherlands-based TNO, with 1993 as the reference year. The figures forGermany, Portugal, Luxembourg and Austria have been updated to reflect the status in 1998.
TABLE 1STATUS OF THE INCINERATION OF SOLID WASTE IN EUROPE
Country

Incineration capacity per country
Mg ● 106 /yshare ofincineration

No of MSW incinerators

Austria

0.513

∼20%

3

Belgium

2.24

∼35%

24

Denmark

2.31

∼75%

30

Finland

0.07

∼4%

1

France

11.33

∼45%

225

Greece0-0Germany

14

∼32%

59

Ireland

0

-

0

Italy

1.9

∼7%

28

Luxembourg

0.125

∼95%

1

Netherlands

3.15

∼27%

10

Norway

0.5

n.d.

18

Portugal

0.5

n.d.

2

Spain

0.74

∼5%

14

Sweden

1.86

∼40%

21

Switzerland

2.84

∼100%

30

UK

3.67

∼2%

31

West-Europe total

45.748-497

EU total

42.408-449

The compilation presented below (figure 1) shows that the calorific values of mixed municipal solid waste in other countries differ verymuch and range from 3,500 to 15,000 kJ/kg.

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Figure 1

Compilation of calorific values from MSW in different
countries

C a lo r ific v a lu e s o f m u n ic ip a l s o lid w a s te in o th e r C o u n tr ie s
C H IN A
KOREA
B R A Z IL
T A IW A N
S IN G A P U R
JA P A N
E U R O P E w ith o u t S w is sUSA
S W IS S

S o u rc e : M a rtin G m b H , M ü n c h en c o m p an y b ro c h u re “ T h e rm isc h e B e h a n d lu n g u n de n e rg e tis c h e V e rw e rtu n g v o n A b fall” , p a g e 5 , 1 9 9 7

1.1.2

MSW incineration in Europe (example Germany)

The thermal treatment of solid municipal waste mostly takes place in plants equipped with grate firing systems, inindividual cases, in pyrolysis, gasification or fluidized bed plants or in plants using a combination of these process
stages. Residual municipal waste (domestic refuse, commercial waste similar to domestic refuse, bulky waste, roadsweepings, market waste, etc.) is delivered to grate furnaces as a heterogeneous mixture of wastes. Combustible
components account for a content of about 40 - 60 wt. percentage. Since the municipal waste incinerated is aheterogeneous mixture of wastes, in terms of sources of CO2, a distinction is drawn between carbon of biogenic
and carbon of fossil origin. The calorific value of mixed waste ranges from 7,500 to 11,000 kJ/kg. The waste's
carbon content is generally in the range of 28 - 40 wt. percent (averages, related to dry matter).
Treatment in incineration plants is an output-controlled process (geared, as a rule, to steam output). The
combustion temperature of the gases in the combustion chamber as measured for at least two seconds after the last
injection of combustion air is usually at least 850°C. The oxygen necessary for incineration is supplied via ambient
air, as primary, secondary and/or tertiary air. The volume of air supplied to the incinerator is between 3,000 and
4,500 m3 (dry) per Mg of waste. This gives a waste gas volume of 3,500 - 5,500 m3 (dry) per Mg of waste.
At almost all municipal waste incineration plants, the heat produced during incineration is utilised for steam
generation. Upon reaching the end of the steam generator, the temperature of the waste gas has been reduced to200° C. The steam produced in municipal waste incinerators exhibits pressures between 14 and 120 bar andtemperatures between 196 and 525°C. Common steam parameters are 40 bar and 400°C. A high heat utilisation
efficiency can only be achieved if incineration is controlled so that the produced amounts of steam can be madeavailable continuously for direct supply of heat and electricity to an industrial plant or for use in a heating station orcogeneration plant.

1.1.3

Hazardous waste incineration in Europe (example
Germany)

Hazardous waste is treated almost exclusively by incineration. Incineration must be understood here as an elementof comprehensive logistics for the treatment of those wastes which due to their harmful nature have to be managed
separately from municipal waste. Hazardous waste is waste requiring particular supervision, which by its nature,
condition or amount poses a particular hazard to health, air and/or water or is particularly explosive, or may
contain or bring forth pathogens of communicable diseases. Since hazardous waste is generated for the most part inindustrial production, notably the chemical industry, it is also referred to as industrial waste or industrial residue.
Hazardous wastes occur, for example, as residues from petrochemical distillation processes, as undesirable
by-products of syntheses processes of the basic organic chemical industry and the pharmaceutical industry as well

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as in the recovery and disposal of contaminated or post-expiration-date products such as solvents, paints or wasteoil. In addition, environmental protection measures such as regulations prohibiting PCBs, CFCs or halons may
generate streams of hazardous waste. The waste going to incineration is usually a mixture of waste types which
may differ in composition and be present in solid, semi-liquid or liquid form. Its chemical description differs fromthat of municipal waste. As hazardous wastes are of varying consistency, the rotary kiln is widely used as auniversally applicable incineration process. Only in exceptional cases are hazardous wastes incinerated in aconventional combustion chamber, a muffle-type furnace or other type of incineration system. The rotary kiln
operates according to the parallel-flow principle, in which the material being incinerated and the combustion gas
are transported in the same direction, from the cold to the hot side. With combustion temperatures between 800 and
1200°C, the residence time of solids in the rotary kiln is up to 1 hour while for the combustion gases it is only a few
seconds. The waste gas generated during the combustion process is fed to an after burning chamber, in which theminimum temperature of between 850 and 1200°C is maintained for a residence time of at least 2 seconds. The
waste gas volume from this process is generally assumed to be about 7,000 m3 (dry) per Mg of waste.
At nearly all hazardous-waste or residues incineration plants, the heat produced during incineration is utilised forsteam generation downstream from the afterburner. Upon reaching the end of the steam generator, the temperatureof the waste gas has been reduced to 200-300°C. The steam from hazardous-waste incineration exhibits pressures
between 17 and 30 bar and temperatures between 250 and 300°C.

1.1.4

Mono-incineration of sewage sludge in Europe (example
Germany)

The system mainly used for the incineration of sewage sludge is fluidized-bed combustion. Most plants are
stationary fluidized-bed furnaces, but there are also multiple-hearth furnaces and multiple-hearth fluidized-bed
furnaces in use. Fluidized-bed furnaces for the incineration of sewage sludge are usually operated at combustion
temperatures in the range of 850°C and 900°C. The waste gas volume from this process is generally assumed to beabout 8,000 m3 (dry) per Mg. of sewage sludge (dry matter). Modern plants are equipped with a steam generator
downstream from incineration, producing wet steam with a pressure of 10 bar and a temperature of 180°C. Most
plants use the produced steam to meet in-plant requirements (e.g. for sludge drying).
The sewage sludge delivered to the incineration plants in de-watered and/or partially dried condition usually has awater content of 50-70 percent. The calorific value of de-watered sludge averages 3,500 kJ/kg in the case of raw
sludge (25 percent dry matter) and 2,500 kJ/kg in the case of digested sludge (25 percent dry matter). The content
of mineral and inorganic components in sludge can be as high as 30 percent. The carbon content of sludge is
generally about 30 percent.

1.1.5

Co-incineration in Europe

In the future, the use of waste in plants other than waste incineration plants will be gaining in importance as a waste
management option. The object of co-incinerating high-calorific waste as substitute fuel (so-called waste forenergy recovery) in production (e.g. cement works, brick manufacture, blast furnace), power plants (e.g. use of
sewage sludge in coal-fired power plants) and industrial boilers is the substitution of regular fuel (coal, fuel oil,etc.) and to reduce energy costs.
The climate-relevant emissions of a waste incineration plant are made up of a proportion to be allocated to thewaste's contribution to the thermal output and that of the remaining regular fuel. Therefore, a proportions
calculation has to be carried out to determine the proportion of those climate-relevant emissions which result fromthe co-incineration of the waste.

1.1.6

Other kinds of waste incineration

In most European countries, the use of incineration plants for medical waste or as crematoria is for the combustion
capacity and the climate-relevant emission of flue gas stream not so relevant. For that reason this kind ofincineration will not be considered in this paper.
(From a waste management perspective, merely dividing the total CO2 load produced by a waste incineration plant
into carbon compounds of biogenic and carbon compounds of fossil origin is too simple a view. It fails to take into
account that waste of biogenic origin. It includes a fossil component from the product life-cycle. That component
stems from manufacture and transport (e.g. of textiles, paper and cardboard, composites, wooden furniture ⇒bulky waste) and needs to be allocated and charged to the product/waste fraction as climate-relevant. Whenreporting emissions according to the Revised 1996 IPCC Guidelines for National Greenhouse Gas for National
Inventories (IPCC Guidelines) however, these emissions are included in the energy sector and should therefore not
be included in the waste emission.)

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2

METHODOLOGICAL ISSUES

2.1

Proposed methodology to calculate theemissions from waste incineration(The values of the calculation shall be standardised on the following conditions: dry gas, 11 percent O2, 273 K,
1013 hPa).
Equation 1 calculates the emissions from waste incineration plants:
EQUATION 1
Emissions i [Mg ] = emission concentration i [Mg ● 10-9/m3]● exhaust gas volume (dry) [m3/Mg waste]● amount of incinerated waste [Mg waste]
Where:
Emission i in [Mg emission]i ≅ CO2, N2O, CH4, NOx, CO, TOC, NH3
emission concentration i [Mg • 10-9/ m3] of the climate-relevant emission according to chapter 2.2
i ≅ CO2, N2O, CH4, NOx, CO, TOC, NH3
exhaust gas volume (dry) [m3/Mg waste] of the incineration plant according to chapter 2.4
amount of incinerated waste [Mg waste] of a country per year.
Equation 2 calculates the emissions in CO2-equivalent:
EQUATION 2
Emissions in CO2-equivalent i [Mg CO2] = Emission i [Mg emission]● GWP [Mg CO2/Mg emission]
Where:
Emissions in CO2-equivalent i [Mg CO2]
Emission i [Mg emission] of Formula (1)i ≅ CO2, N2O, CH4, NOx, CO, TOC, NH3
global warming potential GWP in [Mg CO2/Mg emission] according to chapter 2.3

2.2

Choice of emission factor and activity data

Carbon Dioxide CO2
The incineration of 1 Mg of municipal waste in MSW incinerators is associated with the production/release ofabout 0.7 to 1.2 Mg of carbon dioxide CO2. Although this carbon dioxide is directly released into the atmosphereand thus makes a real contribution to the greenhouse effect, only the climate-relevant CO2 emissions from fossil
sources are considered for the purposes of a global analysis. Since the municipal waste incinerated is aheterogeneous mixture of wastes, in terms of sources of CO2 a distinction is drawn between carbon of biogenic andcarbon of fossil origin. In the literature, the proportion of CO2 assumed to be of fossil origin (e.g. plastics) andconsequently to be considered as climate-relevant, is given as 33 to 50 percent.
Assuming that carbon dioxide emissions from MSW incineration average 1 Mg per Mg of waste, then of these CO2
emissions 0.33 (0.50) Mg are of fossil and 0.67 (0.50) Mg are of biogenic origin. In subsequent calculations, theproportion of climate-relevant CO2 is figured out as an average value of 0.415 Mg of CO2 per Mg of waste. The
measured CO2 output content of the exhaust gas (dry) in MSW incineration plants is round about 10 Vol. percent
multiply with 5,500 m3 exhaust gas volume (dry) per Mg waste multiply with 1.9768 kg/ m3 density of CO2 result in
1087 kg CO2 per Mg waste. The content of C in CO2 is round about 27.3 percent resulting in 297 kg C per Mg waste.
Another way to develop the estimate of climate-relevant CO2 emission from the input, was to estimate the amountof non-biogenic carbon in the waste. Usually, three waste categories contain non-biogenic carbon: plastics,
textiles, and a combined category for rubber and leather (U.S. EPA 1997).But it is a problem to determine the real

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content of carbon in the heterogeneous MSW, because it is variable from day to day. The waste's carbon content ofGerman MSW is generally in the range of 28 - 40 wt .percent (averages, related to dry matter) or 280 - 400 kg C per
Mg waste.
Calculation example (Germany MSW incinerated 14 ● 106 Mg waste/ year):
Equation 1:
Total Emission CO2 = 0.415 Mg CO2 /Mg waste ● 14 ● 106 Mg waste/ year
Total Emission CO2 = 5.81 ● 106 Mg/year
Equation 2:
Total emission CO2 = 5.81 ● 106 Mg CO2 /year
For the incineration of sewage sludge in fluidized-bed plants, an emission of 1 Mg of CO2 per Mg of incinerated
sludge (dry matter) is assumed.
Nitrous Oxide N2O
As well as the above nitrogen oxide compounds NO and NO2, nitrous oxide N2O is of relevance from a climate
perspective. Emission levels of 1 to 12 mg/m3 have been determined in individual measurements at MSW
incineration plants, with an average of 1 - 2 mg/m3. From hazardous waste incineration plants the emission levelsof 30 to 32 mg/m3 have been determined in individual measurements.
NO2 emission levels (individual measurements) are markedly higher in the incineration of sewage sludge influidized-bed plants. An average of 100 mg N2O/m3 was used for the calculations presented here.
Calculation example:
Equation 1:
Total Emission N2O = 2 mg/m3 ● 5,500 Nm3 /Mg waste ● 14 ● 106 Mg waste/year
Total Emission N2O = 154 Mg/year
Equation 2:
Total emission CO2-equivalent = 154 Mg N2O/y ● 310 Mg CO2 /Mg N2O
Total emission CO2-equivalent N2O = 0.04774 ● 106 Mg CO2 /year
Methane CH4
It can be assumed that under the oxidative combustion prevailing in waste incineration in MSW incinerators,
methane is not present in the waste gas and consequently is not emitted. Although methane emissions may form in
the waste bunker, the underpressure in the waste bunker causes them to be transported with the bunker air to the
combustion chamber as primary air, to be converted there.
Calculation example:
Equation 1:
Total Emission CH4 = 0
Equation 2:
Total emission CO2-equivalent CH4 = 0

2.2.1

Other climate-relevant emissions from MSW incineration(NOT relevant for IPCC methodology)

Carbon Monoxide CO
During the incineration of municipal waste in MSW incinerators carbon monoxide is formed as the product ofincomplete combustion. CO is an indicator substance for the combustion process and an important quality criterion
for the level of combustion of the gases. As a rule, CO is measured continuously in the plants. Average CO
emissions, as daily means, are below 50 mg/ m3. Plants reflecting BAT (Best Available Techniques) have dailymeans in the range of <10 mg/ m3.

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Calculation example:
Equation 1:
Total Emission CO = 50 mg/m3 ● 5,500 Nm3 /Mg waste ● 14 ● 106 Mg waste/year
Total Emission CO= 3.85 ● 103 Mg/year
Equation 2:
Total emission CO2-equivalent = 3.85 ● 103 Mg CO/y ● 3 Mg CO2 /Mg CO
Total emission CO2-equivalent CO = 0.01155 ● 106 Mg CO2 /year
Nitrogen Oxides NOx
In the incineration of municipal waste in MSW incinerators nitrogen oxides NOx (NO, NO2) arise, which areformed essentially from the nitrogen contained in the waste, from the combustion process itself and fromspontaneous reaction (so-called prompt NOx). As a rule, nitrogen oxide concentrations in waste gas are measured
continuously at these plants. If no measures were performed at MSW incinerators for nitrogen removal, theemissions would be between 350 and 400 mg/m3. An emission level of 200 mg/m3 can safely be attained if
selective waste gas treatment measures are carried out (SNCR, SCR). Plants reflecting BAT (best available
techniques) attain emission levels in the range of 100 to 150 mg NOx/m3 when using SNCR technology and <70
mg NOx/m3 when using SCR technology.
Hazardous waste incineration plants reflecting BAT attain emission levels in the range of 40 to 50 mg NOx/m3
when using SCR technology.
Calculation example:
Equation 1:
Total Emission NOx = 0.2 ● 103 mg/m3 ● 5,500 Nm3 /Mg waste ● 14 ● 106 Mg waste/year
Total Emission NOx = 15.4 ● 103 Mg/year
Equation 2:
Total emission CO2-equivalent = 15.4 ● 103 Mg NOx/y ● 8 Mg CO2 /Mg NOx
Total emission CO2-equivalent NOx = 0.123 ● 106 Mg CO2 /year
Ammonia NH3
In MSW combustion, emissions of ammonia NH3 arise in particular from the use of ammonia (and also ammonia
water) as an additive in waste gas treatment measures for nitrogen removal (SNCR, SCR). As a rule, emissions(determined in individual measurements) are in the range of 1-10 mg/m3; the average is assumed to be 4 mg NH3/m3.
Calculation example:
Equation 1:
Total Emission NH3 = 4 mg/m3 ● 5,500 Nm3 /Mg waste ● 14 ● 106 Mg waste/year
Total Emission NH3 = 308 Mg/year
Equation 2:
Total emission CO2-equivalent NH3 = n.d.
Non-Methane Volatile Organic Compounds ( NMVOCs)
Organic compounds (organic C) in the waste gas of MSW incineration plants are measured continuously as sum
parameter Total Carbon. This parameter constitutes an indicator of the level of combustion achieved in an
incineration process. The emissions are subject to a limit of 10 mg/ m3, but BAT plants attain, as a rule, emission
levels of 1 mg/ m3.
Calculation example TOC:
Equation 1:
Total Emission TOC= 5 mg/ m3 ● 5,500 N m3 /Mg waste ● 14 ● 106 Mg waste/year
Total Emission TOC= 385 Mg/year

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Equation 2:
Total emission CO2-equivalent = 385 Mg TOC/y ● 11 Mg CO2 /Mg TOC
Total emission CO2-equivalent TOC = 0.004235 ● 106 Mg CO2 /year

2.3

Estimation of the specific emissions of a power
plant mix per kWh Net (related to total
electricity consumption) and the global
warming potential (GWP)

The specific emissions data, in mg/kWh, refer to the total amount of electricity produced in all public power plants,
based on a power plant mix consisting of fossil-fuelled power plants (gas, oil, coal), nuclear power plants andpower plants operated with renewable energy sources (hydro, wind, solar). They are used to make a global
estimate at country level (in the present case, Germany) of the specific climate-relevant emissions from the power
plant sector. For local-level analyses, instead of the electricity-related power plant mix more specific emission
factors (related to the energy carrier actually being replaced) should be used in the calculations to determine thesubstitution effect of energy produced in waste incineration (Table 2).
TABLE 2EMISSION FACTORS FOR POWER PLANT MIX
Emission

2.4

Emission factor (power plant mix)
[mg/kWh]][kg CO2/kg emission]]

GWP (100 years)

CO2690,000

1

N2O

32

310

CO

235

3

NMVOC

13

11

NH3

7

not defined

NOx

660

8

CH4

13

21

Exhaust gas volumes in waste incineration

Waste incineration plants have different exhaust gas volumes. This depends on the kind of the process and thecomposition of waste. Table 3 shows the usual exhaust gas volumes in MSW incineration plants, hazardous waste
incineration plants and mono-sewage sludge incineration plants.
TABLE 3
DIFFERENT EXHAUST GAS VOLUMES IN WASTE INCINERATION PLANTS
Exhaust gas volume (dry)3Municipal solid waste incineration

5,500 m3/Mg waste

Hazardous waste incineration

7,000 m3/Mg waste

Mono sewage sludge incineration

8,000 m3 /Mg sewage sludge dry matter

REPORTING AND DOCUMENTATION

Transparency will be improved if all countries report estimates for their waste incineration activities separately,
and indicate whether they use Tier 1, Tier 2, or Tier 3 methods.

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4

INVENTORY QA/QC

4.1

Internal inventory QA/QC systems

Quality of the data used to calculate climate-relevant emissions:Tier 1 Emissions data for the waste gas parameters NOx, CO, Total Organic Carbon are determined by continuous
measurements in the waste incineration plants, monitored by the competent licensing authorities and published ona yearly basis.
Municipal solid waste is heterogeneous (a composite of many waste components). A determination of theclimate-relevant chemical substances contained in the waste input, cannot be specifically stated, due to the fact that
MSW analysis can only make individual conclusion and not general statements (due to their permanent changing
as non-homogenous composition). The method proposed here for estimation of the climate-relevant total
emissions is therefore based on exhaust gas measurements. These output measurements can be more exactly
defined as the waste input analysis.
Tier 2 Emissions data for the waste gas parameter CO2 are calculated on the basis of waste analyses, and emissions
data for NH3 and N2O are determined by individual measurements.
Tier 3 The specific emissions factors, related to electricity consumption, for climate-relevant emissions of thepower plant mix have been calculated on the basis of energy statistics and annual reports of the energy industry.
The specific waste gas volumes generated in the various treatment processes have been calculated from theoperators' data on waste gas volume and the associated waste throughputs. Uncertainty is involved in determining
the proportion of climate-relevant CO2 from waste incineration for the purpose of calculating total climate-relevant
CO2 emissions, since the range of variation in the proportion of CO2 from waste of biogenic origin leaves ample
scope for subjective judgement. One has to largely draw upon literature data from analyses for the carbon content
in waste, its distribution among the various waste fractions, associated assumptions with respect to waste
composition, and estimates based thereon.
The results of the calculation in Annex 1 shows, that the determination of the energy actually substituted in acountry by waste incineration is likewise subject to a great deal of uncertainty. Energy-related data (calorific valueof the waste, utilisation of waste-derived energy) and possible efficiencies vary widely. They are determined by
the site conditions and the geographical location, and have a considerable influence on the energy credits to be
deducted from the total emissions determined.
The comparison of the total emissions calculated according to formulas (1) and (3) allows a criterion to be obtained
for the assessment of modern waste incineration with and without energy use which takes into account thesubstituted primary energy potential.
Using the climate-relevant CO2 equivalents calculated according to formulas (2) and (4), the climate-relevant
emissions of waste incineration plants can be added up as CO2 equivalents to enable an overall assessment.
CO2 constitutes the chief climate-relevant emission of waste incineration and is considerably higher, by not lessthan 102, than the other emissions.
An energy transformation efficiency equal to or greater than about 25 percent results in an allowable average
substituted net energy potential that renders the emission of waste incineration plants (calculated as CO2
equivalents) climate-neutral due to the emission credits from the power plant mix.

5

CONCLUSIONS

The incineration of municipal waste involves the generation of climate-relevant emissions. These are mainly
emissions of CO2, but also of N2O, NOx, NH3, and organic C, measured as total carbon. CH4 is not generated inwaste incineration during normal operation. It only arises in particular, exceptional, cases and to a small extent(from waste remaining in the waste bunker), so that in quantitative terms CH4 is not to be regarded asclimate-relevant.
In waste incineration plants, CO2 constitutes the chief climate-relevant emission and is considerably higher, by notless than 102, than the other climate-relevant emissions.
In Germany the incineration of 1 Mg of municipal waste in MSW incinerators is associated with the
production/release of about 0.7 to 1.2 Mg of carbon dioxide (CO2 output). The proportion of carbon of biogenic

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origin is usually in the range of 33 to 50 percent. The climate-relevant CO2 emissions from waste incineration aredetermined by the proportion of waste whose carbon compounds are assumed to be of fossil origin. The allocation
to fossil or biogenic carbon has a crucial influence on the calculated amounts of climate-relevant CO2 emissions.
In Germany, every waste incineration plant is equipped with facilities to utilize energy. A factor that has a decisive
influence on the calculated amounts of climate-relevant emissions from waste incineration plants with energy
utilisation is the credit allowed or allowable due to the substitution of energy from fossil fuels. The latter in turn is
influenced by the energy carriers used as a basis to calculate the emission factor of the power plant mix.
An energy transformation efficiency equal to or greater than about 25 percent results in an allowable average
substituted net energy potential that renders the emission of waste incineration plants (calculated as CO2
equivalents) climate-neutral due to the emission credits from the power plant mix.

REFERENCES
Energy from waste plants 1994, General/Technical Information, ISWA Working group on thermal treatment ofwaste, December 1994, ISWA General Secretariat DK-1069 Copenhagen K, Denmark, reporter for Germany:
Dr. D.O. Reimann, Bamberg, Pages 39-52
EU Report: Economic Evaluation of the Draft Incineration Directive, A report produced for the European
Commission DGXI, Contract No. B4 3040/95/001047/MAR/B1, December 1996, ETSU
Reimann, D.O., Hämmerli, H.: "Verbrennungstechnik für Abfälle in Theorie und Praxis”, Schriftenreihe
Umweltschutz, Bamberg 1995, Ed.: Dr. D.O. Reimann, Rheinstr. 6, D-96052 Bamberg
Wallmann, R.: "Ökologische Bewertung der mechanisch-biologischen Restabfallbehandlung und derMüllverbrennung auf Basis von Energie- und Schadgasbilanzen”, Schriftenreihe des Arbeitskreises für die
Nutzbarmachung von Siedlungsabfällen (ANS) e.V., ISBN 3-924618-37-2, Vol. 38, April 1999, D-40822
Mettmann

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ANNEX 1METHOD FOR CALCULATION OF ENERGYCREDIT FOR USE OF MSW AS A SUBSTITUTE FOR
FOSSIL FUELS

Discription of a method to calculate the energy credit for the use of waste as a substitute for fossil fuel
(MSW incineration plants with energy recovery)
A 1.1 Formulas to calculate the energy credit for the use of waste as a substitute for fossil fuel (MSW
incineration plants with energy recovery)
Equations 3 and 4 are to be used for the purpose of a comparative evaluation of the climate-relevant emissions
from waste incineration in relation to those of other types of energy production. A factor that has a decisive
influence on the calculated amounts of climate-relevant emissions from waste incineration plants with energy
utilisation is the credit allowed or allowable due to the substitution of energy from fossil fuels. The latter in turn is
influenced by the energy carriers used as a basis to calculate the emission factor of the power plant mix.
Equation 3 corrects the total emissions from Equation 1 for the use of waste as substitute fuel (for incineration
plants with energy recovery):
EQUATION 3
Total emission i cor [Mg emission] = total emission i [Mg emission] - usable/used energy [kWh]● emission factor (power plant mix) [Mg emission ● 10-9/kWh]
Where:
Total emission i cor in [Mg emission] for incineration plants with energy recoveryi ≅ CO2, N2O, NOx, CO, TOC, CH4, NH3, etc.
total emission i [Mg emission] of Formula (1)i ≅ CO2, N2O, NOx, CO, TOC, CH4, NH3, etc.
usable/used energy [kWh] different for every country according to A 1.2 and A 1.3 in this annex.
emission factor (power plant mix) [Mg emission ● 10-9/kWh] for the climate-relevant emissions of
substituted energy from fossil fuel according to chapter 2.3
Equation 4 adds the calculated correct climate-relevant total emission as CO2-equivalent (for incineration plants
with energy recovery):
EQUATION 4
Total emission CO2-equivalent i cor [Mg CO2] = total emission i cor [Mg emission]● GWP [Mg CO2/Mg emission]
Where:
Total emission CO2-equivalent i cor [Mg CO2]
total emission i cor [Mg emission] from Formula (3)global warming potential (GWP) [Mg CO2/Mg emission] according to chapter 2.3

Calculation example CO2 :Equation 3:
Total Emission CO2 cor= 5.81 ● 106 Mg /year - 8.75 ● 109 kWh/year ● 690,000 mg CO2 /kWhTotal Emission CO2 cor= 5.81 ● 106 Mg CO2 /year - 6.0375 ● 106 Mg CO2 /year (energy credit)

Total Emission CO2 cor= - 0.2275 ● 106 Mg CO2 /year

Equation 4:
Total emission CO2 cor= - 0.2275 ● 106 Mg CO2 /year

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Calculation example NOx :Equation 3:
Total Emission NOx cor =15.4 ● 103 Mg/year - 8.75 ● 109 kWh/year ● 660 mg NOx/kWh

Total Emission NOx cor =15.4 ● 103 Mg /year - 5.775 ● 103 Mg/year (energy credit)

Total Emission NOx cor =9.625 ● 103 Mg NOx/year

Equation 4:
Total emission CO2-equivalent NOx cor = 9.625 ● 103Mg NOx/year ● 8 Mg CO2 /Mg NOx
Total emission CO2-equivalent NOx cor = 0.077 ● 106 Mg CO2 /year

Calculation example N2O :Equation 3:
Total Emission N2O co r =154 Mg /year - 8.75 ● 109 kWh/year ● 32 mg N2O /kWhTotal Emission N2O cor =154 Mg /year - 280 Mg /year (energy credit)

Total Emission N2O cor =-126 Mg/year

Equation 4:
Total emission CO2-equivalent N2O cor = - 126 Mg N2O /year ● 310 Mg CO2 /Mg N2O
Total emission CO2-equivalent N2O cor = - 0.03906 ● 106 Mg CO2 /year

Calculation example CO :Equation 3:
Total Emission COcor= 3.85 ● 103 Mg/year - 8.75 ● 109 kWh/year ● 235 mg CO/kWh

Total Emission COcor= 3.85 ● 103 Mg/year - 2.05 ● 103 Mg/year (energy credit)

Total Emission COcor= 1.8 ● 103 Mg/year

Equation 4:
Total emission CO2-equivalent COcor = 1.8 ● 103Mg CO/year ● 8 Mg CO2 /Mg CO
Total emission CO2-equivalent COcor = 0.0054 ● 106 Mg CO2 /year

Calculation example TOC:
Formula (3)Total Emission TOCcor= 385 Mg /year - 8.75 ● 109 kWh/year ● 13 mg TOC/kWh

Total Emission TOCcor= 385 Mg /year - 113.75 Mg /year (energy credit)

Total Emission TOCcor= 271.25 Mg/year

Formula (4)Total emission CO2-equivalent TOCcor = 271.25 Mg TOC/year ● 8 Mg CO2 /Mg TOC
Total emission CO2-equivalent TOCcor = 0.002983 ● 106 Mg CO2 /year

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Calculation example NH3 :Equation 3:
Total Emission NH3 cor= 308 Mg /year - 8.75 ● 109 kWh/year ● 7 mg NH3/kWh

Total Emission NH3 cor= 308 Mg /year - 61.25 Mg /year (energy credit)

Total Emission NH3cor= 246.75 Mg/year

Formula 4:
Total emission CO2-equivalent NH3cor = n.d.

Calculation example CH4 :Equation 3:
Total Emission CH4= 0 - 8.75 ● 109 kWh/year ● 13 mg CH4/kWh

Total Emission CH4= 0 - 113 Mg/year

Total Emission CH4 cor = - 113 Mg/year
Equation 4:
Total emission CO2-equivalent CH4 cor = - 113 Mg CH4/year ● 21 Mg CO2 /Mg CH4
Total emission CO2-equivalent CH4 cor = - 0.002373 ● 106 Mg CO2 /year
A1.2

Energy utilisation efficiency of (energy supplied by) different MSW incineration plants

In general, about 300 to 600 kWh of electricity can be produced in a MSW incineration plant from 1 Mg ofmunicipal waste, depending on plant size, steam parameters and steam utilisation efficiency. In the case of theco-generation of electricity and heat, about 1,250 kWh of heat per Mg of waste can be produced in addition andsupplied to external users, depending on the incineration plant's site-dependent heat supply opportunities as well as
the geographical location of the country and the (long-distance) heat utilisation periods usual for that country (e.g.
in Germany, 1,300-1,500 hrs/year out of a possible 8,760 hrs/year). Given ideal site conditions with favourable
opportunities for utilisation and supply in the form of steam, electricity and hot water or exclusively steam, thetransformation/recovery efficiency of an incineration plant operating at base load can be increased to a maximumof 75-83 percent of the energy input (calorific value). In this energetically favourable case, about 2 MWh, asenergy mix (electricity and heat), per Mg of waste can be produced and supplied to external users.
Actual energy transformation efficiencies are shown in the Table 4 below, ranging from a site with minimum
supply of energy (electricity only) to sites with normal or optimised power/heat co-generation or exclusively
supplying heat. This broad range of variation among existing plants illustrates that the energy transformation
efficiency as well as the proportion of energy actually supplied by waste incinerators to substitute for fossil energy
sources, as estimated on the basis of it, and the resultant emissions, are of major importance to the calculation ofclimate-relevant emissions.
TABLE 4ENERGY TRANSFORMATION/RECOVERY EFFICIENCIES (W) OF THE GROSS ENERGY INPUT OF MSW INCINERATORS
minimum energy
recoverynormal energy
recovery

optimised energy
recovery

optimised energy
recovery

W thermal (%)<1

11

15 - 55

70-83

W electrical (%)

13

14

20

0

W total (%)

1325

35 - 75

70-83

A1.3

Status of Waste Incineration and Energy Use in Germany

In Germany an amount of approx. 14 ● 106 Mg/a of residual waste is subjected to thermal treatment (status: 1999).
For waste incineration plants in Germany, a theoretical gross energy content in municipal waste, in kJ/a, can be
specified by multiplying an assumed average calorific value of about 9 ●106 kJ per Mg of waste, roughly reflecting
as a rule the calorific value of low-quality lignite, by the amount of waste incinerated annually. From this, theEmissions from Waste Incineration

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energy made available by waste incineration can be calculated as a function of the assumed energy transformation
and utilisation efficiency (the average from all plants in Germany is in the range of 20 to 35 percent) to derive
conclusions as to the relevance of waste-derived energy for the substitution of climate-relevant emissions fromfossil energy sources. The waste incineration plant's own energy (electricity, etc.) requirements (e.g. for waste gas
treatment) are considered to be external energy which in the ideal case would be met through in-plant electricity
production.
Taking Germany as an example, the credit for energy from waste incineration is calculated as follows:
Amount of residual waste subjected to thermal treatment: approx. 14 ● 106 Mg/a,multiplied by an average calorific value of approx. 9 ● 106 kJ/Mg waste
gives 126 ● 1012 kJ, or 126 ● 106 GJ/a;divided by 3.6 GJ/MWh
gives 35 ● 106 MWh/a.
Of this amount, an average of 35 ● 106 MWh/a ● 0.25 total energy transformation efficiency is utilised, whichbrings the average allowable substituted net energy potential to 8.75 ● 106 MWh/a (normal energy recovery).
Based on 1992 operating data taken from the ISWA's data compilation "Energy from Waste Plants 1994", theenergy supplied to external users in the form of heat and electricity by waste incineration plants in Germany(incineration capacity 7.3 ● 106 Mg/a) can be calculated at approx. 4.8 ● 106 MWh/a.
If the total emission of the non-biogenic CO2 is estimate with 0.414 Mg CO2 per Mg waste and the average totalenergy transformation efficiency of all waste incineration plants with energy recovery were optimised to reach avalue equal to or greater than about 0.25, the allowable substituted net energy potential would increase to 8.75 ●106 MWh/a (normal energy recovery), leading to neutrality in climate-relevant emissions from waste incineration
due to the emission credits from the power plant mix.
A 1.4 Comparison example of the climate-relevant total emission from MSW Incineration in Germany
with or without energy recovery
Results of the amount of calculation from Equations 1, 2, 3, and 4 - Table 5
CO2 constitutes the chief climate-relevant emission of waste incineration and is considerably higher, by not lessthan 102, than the other emissions.
TABLE 5SW INCINERATION IN GERMANY (THROUGHPUT 14 ● 106 MG/YEAR)
Emission

W=0

W = 25%

W=0

W = 25%

Total Emission (1)Total Emission cor (3)Total Emission (2)Total Emission cor (4)[Mg/year]][Mg/year]][Mg CO2/year]][Mg CO2/year]]6- 0.2275 ● 106

5.81 ● 10NOx

0.0154 ● 106

0.009625 ● 106

0.123 ● 106

0.077 ● 106

N2O

0.000154 ● 106

0.000126 ● 106

0.0477 ● 106- 0.039 ● 106

CO

0.00385 ● 106

0.0018 ● 106

0.0115 ● 106

0.0054 ●106

TOC

0.000385 ● 106

0.00027125 ● 106

0.0042 ● 106

0.0029 ● 106

NH30.000308 ● 106

0.00024675 ● 106

not definedNot defined0- 0.00237 ● 106

5.99 ● 106 Mg CO2
per year-0.18 ● 106 Mg CO2
per year00.000113 ● 10

6

Amount of total emission as CO2 equivalent from MSW Incineration

5.81 ● 10

6

CO2

CH4

- 0.2275 ● 10

6

An energy transformation efficiency equal to or greater than about 25 percent results in an allowable average
substituted net energy potential that renders the emission of waste incineration plants (calculated as CO2
equivalents) climate-neutral due to the emission credits from the power plant mix.

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