5.1
CGEGreenhouse Gas Inventory
Hands-on Training Workshop
WASTE SECTOR
5.2
Overview Introduction IPCC 1996GL (Revised 1996 IPCC Guidelines for National
Greenhouse Gas Inventories) and GPG2000 (Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories)
Reporting framework Key source category analysis and decision trees Tier structure, selection and criteria Review of problems
Methodological issues Activity data Emission factors
IPCC 1996GL category-wise assessment and GPG2000 options Examination and assessment of activity data and emission
factors: data status and options Uncertainty estimation and reduction
5.3
Introduction
5.4
Introduction
COP2 adopted guidelines for preparation of initial national communications (decision 10/CP.2)
IPCC guidelines used by 106 NAI Parties to prepare national communications
New UNFCCC guidelines adopted at COP8 (decision 17/CP.8) provided improved guidelines for preparing GHG inventory
UNFCCC User Manual for guidelines on national communications to assist NAI Parties in using latest UNFCCC guidelines
Review and synthesis reports of NAI inventories highlighted several difficulties and limitations of using IPCC 1996GL (FCCC/SBSTA/2003/INF.10)
GPG2000 addressed some of the limitations and provided guidelines in order to reduce uncertainties
5.5
Purpose of this Handbook
GHG inventories are mostly biological sectors, such as Waste, and characterized by:
methodological limitations lack of data or low reliability of existing data high uncertainty
This handbook aims at assisting NAI Parties in preparing GHG inventories using the IPCC 1996GL, particularly in the context of UNFCCC decision 17/CP.8, focusing on:
the need to shift to GPG2000 and higher tiers/methods to reduce uncertainty
complete overview of the tools and methods use of IPCC inventory software and EFDB review of AD and EF and options to reduce uncertainty use of key sources, methodologies and decision trees
5.6
Target groups
NAI inventory experts
National GHG inventory focal points
5.7
NAI country examples Review of national communications: Argentina,
Colombia, Chile , Cuba and Panama GHG inventories show that the Waste sector
may be significant in NAI countries Commonly a significant source of CH4
In some cases a significant source of N2O Solid waste disposal sites (SWDS) frequently a
key source of CH4 emissions
5.8
Definitions Waste emissions – Includes GHG emissions
resulting from waste management activities (solid and liquid waste management, excepting CO2 from organic matter incinerated and/or used for energy purposes).
Source – Any process or activity that releases a GHG (such as CO2, N2O, CH4) into the atmosphere.
5.9
Definitions (2) Activity Data – Data on the magnitude of human
activity, resulting in emissions during a given period of time (e.g. data on waste quantity, management systems and incinerated waste).
Emission Factor – A coefficient that relates activity data to the amount of chemical compound that is the source of later emissions. Emission factors are often based on a sample of measurement data, averaged to develop a representative rate of emission for a given activity level under a given set of operating conditions.
5.10
IPCC 1996GL andGPG2000
Approach and steps
5.11
Emissions from waste management
Decomposition of organic matter in wastes (carbon and nitrogen)
Waste incineration (these emissions are not reported when waste is used to generate energy)
5.12
Decomposition of waste Anaerobic decomposition of man-made waste by
methanogenic bacteria Solid waste
Land disposal sites Liquid waste
Human sewage Industrial waste water
Nitrous oxide emissions from waste water are also produced from protein decomposition
5.13
Land disposal sites Major form of solid waste disposal in
developed world Produces mainly methane at a diminishing
rate taking many years for waste to decompose completely
Also carbon dioxide and volatile organic compounds produced
Carbon dioxide from biomass not accounted or reported elsewhere
5.14
Decomposition process Organic matter into small soluble molecules
(including sugars) Broken down to hydrogen, carbon dioxide
and different acids Acids are converted to acetic acid Acetic acid with hydrogen and carbon
dioxide are substrate for methanogenic bacteria
5.15
Methane from land disposal
Volumes Estimates from landfills: 20–70 Tg/yr Total human methane emissions: 360 Tg/yr From 6% to 20% of total
Other impacts Vegetation damage Odours May form explosive mixtures
5.16
Characteristics of the methanogenic process
Highly heterogeneous However, relevant factors to consider:
Waste management practices Waste composition Physical factors
5.17
Waste management practices
Aerobic waste treatment Produces compost that may increase soil carbon No methane
Open dumping Common in developing regions Shallow, open piles, loosely compacted No control for pollutants, scavenging frequent Anecdotal evidence of methane production An arbitrary factor, 50% of sanitary land filling, is
used
5.18
Waste management practices (II)
Sanitary landfills Specially designed Gas and leakage control Scale economy Continued methane production
5.19
Waste composition
Degradable organic matter can vary Highly putrescible in developing countries In developed countries, due to higher paper
and card content, less putrescible This affects stabilization and methane
production Developing countries: 10–15 years Developed countries: more than 20 years
5.20
Physical factors
Moisture essential for bacterial metabolism Factors: initial moisture content, infiltration
from surface and groundwater, as well as decomposition processes
Temperature: 25–40°C required for a good methane production
5.21
Physical factors (II)
Chemical conditions Optimal pH for methane production: 6.8 to 7.2 Sharp decrease of methane production below 6.5 pH Acidity may delay the onset of methane production
Conclusion Data availability is too poor to use these factors for
national or global methane emissions estimates
5.22
Methane emissions
Depend on several factors Open dumps require other approaches Availability and quality of relevant data
5.23
Waste-water treatment
Produces methane, nitrous oxide and non-methane volatile organic compounds
May lead to storage of carbon through eutrophication
5.24
Methane emissions from waste-water treatment
From anaerobic processes without methane recovery
Volumes 30–40 Tg/yr About 8%–11% of anthropogenic methane
emissions Industrial emissions estimated at 26–40 Tg/yr Domestic and commercial estimated at 2 Tg/yr
5.25
Factors for methane emissions
Biochemical oxygen demand (BOD) (+/+) Temperature ( >15°C) Retention time Lagoon maintenance
Depth of lagoon ( >2.5 m, pure anaerobic; less than 1 m, not expected to be significant, most common facultative 1.2 to 2.5 m – 20% to 30% BOD anaerobically)
5.26
Biochemical oxygen demand
Is the organic content of waste water (“loading”)
Represents O consumed by waste water during decomposition (expressed in mg/l)
Standardized measurement is the “5-day test” denoted as BOD5
Examples of BOD5: Municipal waste water 110–400 mg/l Food processing 10 000–100 000 mg/l
5.27
Main industrial sources
Food processing: Processing plants (fruit, sugar, meat, etc.) Creameries Breweries Others
Pulp and paper
5.28
Waste incineration
Waste incineration can produce: Carbon dioxide, methane, carbon
monoxide, nitrogen oxides, nitrous oxides and non-methane volatile organic compounds
Nevertheless, it accounts for a small percentage of GHG output from the waste sector
5.29
Emissions from waste incineration
Only the fossil-based portion of waste to be considered for carbon dioxide
Other gases difficult to estimate Nitrous oxide mainly from sludge
incineration
5.30
IPCC 1996GL Basis of inventory methodology for waste sector
is: Organic matter decomposition Incineration of fossil origin organic material
Does not include concrete calculations for the latter
Organic matter decomposition covers: Methane from organic matter in both liquid and solid
wastes Nitrous oxide from protein in human sewage Emissions of non-methane volatile organic
compounds are not covered
5.31
IPCC default categories
Methane Emissions from Solid Waste Disposal Sites
Methane Emissions from Wastewater treatment Domestic and Commercial Wastewater Industrial Wastewater and Sludge Streams
Nitrous oxide from Human Sewage
5.32
Inventory preparation using IPCC 1996GL
Step 1: Conduct key source category analysis for Waste sector where:
Sector is compared to other source sectors such as Energy, Agriculture, LUCF, etc.
Estimate Waste sector’s share of national GHG inventory Key source sector identification adopted by Parties that have
already prepared an initial national communication, have inventory estimates
Parties that have not prepared an initial national communication can use inventories prepared under other programs/projects
Parties that have not prepared any inventory, may not be able to carry out the key source sector analysis
Step 2: Select the categories
5.33
Inventory preparation using IPCC 1996GL (2)
Step 3: Assemble required activity data depending on tier selected from local, regional, national and global databases, including EFDB
Step 4: Collect emission/removal factors depending on tier level selected from local/regional/national/global databases, including EFDB
Step 5: Select method of estimation based on tier level and quantify emissions/removals for each category
Step 6: Estimate uncertainty involved Step 7: Adopt quality assurance/control procedures and report
results Step 8: Report GHG emissions Step 9: Report all procedures, equations and sources of data
adopted for GHG inventory estimation
5.34
Calculation of methane from solid waste disposal
For sanitary landfills there are several methods: Mass balance and theoretical gas yield Theoretical first order kinetics methodologies Regression approach
Complex models not applicable for regions or countries
Open dumps considered to emit 50%, but should be reported separately
5.35
Mass balance and theoretical gas yield
No time factors Immediate release of methane Produces reasonable estimates if amount
and composition of waste have been constant or slowly varying, otherwise biased trends
How to calculate: Using empirical formulae Using degradable organic content
5.36
Empirical formulae
Assumes 53% of carbon content is converted to methane
If microbial biomass is discounted it reduces the amount emitted
234 m3 of methane per tonne of wet municipal solid waste
5.37
Using degradable organic content (Base of Tier 1)
Calculated from the weighted average of the carbon content of various components of the waste stream
Requires knowledge of: Carbon content of the fractions Composition of the fractions in the waste
stream This method is the basis for the Tier I
calculation approach
5.38
Equation
Methane emission = Total municipal solid waste (MSW) generated
(Gg/yr) x
Fraction landfilled x
Fraction degradable organic carbon (DOC) in MSW x
Fraction dissimilated DOC x
0.5 g C as CH4/g C as biogas x
Conversion ratio (16/12) ) – Recovered CH4
5.39
Assumptions Only urban populations in developing countries
need be considered; rural areas produce no significant amount of emissions
Fraction dissimilated was assumed from a theoretical model that varies with temperature: 0.014T + 0.28, considering a constant 35°C for the anaerobic zone of a landfill, this gives 0.77 dissimilated DOC
No oxidation or aerobic process included
5.40
Example
Waste generated 235 Gg/yr % landfilled 80 % DOC 21 % DOC dissimilated 77 Recovered 1.5 Gg/yr Methane =
(235*0.80*0.21*0.77*0.5*16/12) – 1.5 =19 Gg/yr
5.41
Limitations Main:
No time factor No oxidation considered
DOC dissimilated too high Delayed release of methane under increasing waste
landfilled conditions leads to significant overestimations of emissions
Oxidation factor may reach up to 50% according to some authors, a 10% reduction is to be accounted
5.42
Default method – Tier 1
Includes a methane correction factor according to the type of site (waste management correction factor). Default values range from 0.4 for shallow unmanaged disposal sites (> 5m) to 0.8 for deep (<5m) unmanaged sites; and 1 for managed sites. Uncategorized sites given a correction factor of 0.6
The former DOC dissimilated was reduced from 0.77 to 0.5 - 0.6, due to the presence of lignin
5.43
Default method – Tier 1
The fraction of methane in landfill gas was changed from 0.5 to a range between 0.4 and 0.6, to account for several factors, including waste composition
Includes an oxidation factor. Default value of 0.1 is suitable for well managed landfills
It is important to remember to subtract recovered methane before applying an oxidation factor
5.44
Default method – Tier 1 Good Practice
Emissions of methane (Gg/yr) =[(MSWT*MSWF*L0) -R]*(1-OX) where
MSWT= Total municipal solid waste
MSWF= Fraction disposed at SWDS
L0 = Methane generation potential
R = Recovered methane (Gg/yr)
OX = Oxidation factor (fraction)
5.45
Methane generation potential
L0 = (MCF*DOC*DOCF*F*16/12 (GgCH4/Gg waste))
where:MCF = Methane correction factor (fraction)
DOC = Degradable organic carbon
DOCF = Fraction of DOC dissimilated
F = Fraction by volume of methane in landfilled gas
16/12 = Conversion from C to CH4
5.46
Other approaches
Include a fraction of dry refuse in the equation
Consider a waste generation rate (1 kg per capita per day for developed countries, half of that for developing countries)
Use gross domestic product as an indicator of waste production rates
5.47
GPG2000 Approach
5.48
Theoretical first order kinetics methodologies (Tier 2)
Tier 2 considers the long period of time involved in the organic matter decomposition and methane generation
Main factors: Waste generation and composition Environmental variables (moisture content, pH,
temperature and available nutrients) Age, type and time since closure of landfill
5.49
Base equation
QCH4 = L0R(e-kc - e-kt)
QCH4 = methane generation rate at year t (m3/yr)
L0 = degradable organic carbon available for
methane generation (m3/tonne of waste)
R = quantity of waste landfilled (tonnes)
k = methane generation rate constant (yr-1)
c = time since landfill closure (yr)
t = time since initial refuse placement (yr)
5.50
Good practice equation Time t is replaced by t-x, normalization factor
that corrects for the fact that the evaluation for a single year is a discrete time rather than a continuous time estimate
Methane generated in year t (Gg/yr) = x [(A*k*MSWT(x)*MSWF(x)*L0(x)) * e-k(t-x) ] for x = initial year to t
Sum the obtained results for all years (x)
5.51
Good practice equation Where:
t = year of inventory
x = years for which input should be added
A = (1-e-k)/k; normalisation factor which corrects the summation
k = Methane generation rate constant
MSWT (x)= Total municipal solid waste generated in year x (Proportional to total or urban population if no rural waste collection)
L0(x) = Methane generation potential
5.52
Methane generation rate constant
The methane generation rate constant k is the time taken for the DOC in waste to decay to half its initial mass (half-life)
k = ln2/t½
This requires historical data. Data for 3 to 5 half lives in order to achieve an acceptable result. Changes in management should be taken into account
5.53
Methane generation rate constant
Is determined by type of waste and conditions Measurements go from 0.03 to 0.2 per year,
equivalent to half lives from 23 to 3 years More degradable material and humidity lower
half life Default value: 0.05 per year, or a half life of 14
years
5.54
Methane generation potential
L0(x) = (MCF(x)*DOC(x)*DOCF*F*16/12 (GgCH4/Gg waste))
where:MCF(x) = Methane correction factor in year x (fraction)
DOC (x) = Degradable organic carbon in year x
DOCF = Fraction of DOC dissimilated
F = Fraction by volume of methane in gas generated from landfill
16/12 = Conversion from C to CH4
5.55
Methane emitted Methane generated minus methane recovered
and not oxidized Equation:
Methane emitted in year t (Gg/yr) = (Methane generated in year t (Gg/yr) - R(t))*(1 - Ox)
Where:
R(t) = Methane recovered in year t (Gg/yr)
Ox = Oxidation factor (fraction)
5.56
Practical applications
Base for Tier 2 approach Applied earlier in:
United Kingdom The Netherlands Canada
5.57
Regression approach
From empirical models Statistical and regressional analysis applied
5.58
Uncertainties in calculations
Methane actually produced Are old landfills covered?
Quantity and composition of landfilled waste Is there historical data on waste
composition? Methane actually produced
Are landfill and waste management practices well known?
5.59
Calculations of emissions fromwaste-water treatment
Calculations for industrial and domestic and commercial waste water are based on biochemical oxygen demand (BOD) loading
Standard methane conversion factor 0.22 Gg CH4/Gg BOD is recommended
For nitrous oxide and methane it is possible to base calculation on total volatile solids and apply the simple method used in the agriculture sector
5.60
Methane from domestic and commercial waste water
Simplified approach Data:
BOD in Gg per 1000 persons (default values) Country population in thousands Fraction of total waste water treated anaerobically
(0.1–0.15 as default) Methane emission factor
(default 0.22 Gg CH4/Gg BOD Subtract recovered methane
5.61
Equation
Methane emission =
Population (103) x
Gg BOD5/1000 persons x
Fraction anaerobically treated x
0.22 Gg CH4/Gg BOD –
Methane recovered
5.62
GPG 2000 Approach
5.63
Good practice guidance – Check method
WM = P*D*SBF*EF*FTA*365*10-12 , where:WM = country’s annual methane emissions from domestic
waste water
P = population (total or urban in developing countries)
D = organic load (default 60 g BOD/person/day)
SBF = fraction of BOD that readily settles, default = 0.5
EF = emission factor (g CH4/ g BOD), default =0.6 or 0.25 g CH4/ g COD (chemical oxygen demand) when using COD
FTA = part of BOD anaerobically degraded, default = 0.8
5.64
Check method rationale
SBF is related to BOD from non-dissolved solids, which account for more than 50% of BOD. Settling tanks remove 33% and other methods 50%
Fraction of BOD in sludge that degrades anaerobically (FTA) is related to the processes, aerobic or anaerobic. Aerobic processes and sludge non-methane producing procedures may lead to FTA = 0
5.65
Check method rationale
Emission factor is expressed in BOD, however COD is used in many places
COD is 2 to 2.5 times higher than BOD, so the default values are 0.6 g CH4/ g BOD or 0.25 g CH4/ g COD
Emission factor is calculated from the methane producing factor stated above and the weighted average of methane conversion factor (MCF)
5.66
Methane conversion factor
IPCC guidelines recommends to separate calculations for waste water and sludge. This influences the detailed approach calculation
Excepting sludge sent to landfills or for agriculture, this is not necessary
If no data are available, expert judgement of sanitation engineers may be incorporated: Weighted MCF = Fraction of BOD anaerobically degrades
5.67
Detailed approach
Considers two additional factors: Different treatment methods used and total
waste water treated using each method MCF for each treatment
The final result is the sum of the fractions calculated by the simplified approach, less the recovered methane
5.68
Equation
Domestic and commercial waste-water emissions =
(Methane calculated by simplified approach x
Fraction waste water treated using method i x MCF for method i) - methane recovered
5.69
Methane emissions from industrial waste water
Industrial waste water may be treated in domestic sewer systems or on site
Only on-site calculations are covered in this section, the rest should be added to domestic waste-water loading
Most estimates used are for point sources Focus on key industries is required and default
values are provided
5.70
Emissions from industrial waste-water treatment
Simplified approach: Determine relevant industries (wine, beer, food,
paper, etc.) Estimate waste-water outflow (per tonne of product,
or default) Estimate BOD5 concentration (or default) Estimate the fraction treated Estimate methane emission factor (default 0.22 Gg
CH4/Gg BOD ) Subtract any methane recovered
5.71
Equation
Industrial waste-water emissions =
(waste-water outflow by industry (Ml/yr) x
kg BOD5/I x
Fraction waste water treated anaerobically x 0.22) - Methane recovered
5.72
Detailed approach Similar to the used for estimating methane
emissions from domestic and commercial waste water
Requires knowledge of: Specific waste-water treatments MCF for each factor
5.73
Equation
Industrial waste-water Emissions =
(Waste-water outflow by industry (Ml/yr) x
kg BOD5/l x
Fraction waste water treated using method i x MCF for method i) - Methane recovered
5.74
Uncertainties in calculations
Lack of information about volumes, treatments and recycling
Discharge into surface waters: Not anaerobic (default 0%) Anaerobic (default 50%)
Septic tanks (long retention times: more than 6 months)
Long retention of solids (default 50%) Short retention of solids (default 10%)
Open pits and latrines (default 20%) Other limitations: BOD, temperature, pH and retention
time
5.75
GPG2000 Approach
5.76
Emissions from waste incineration
For carbon dioxide, only fossil fraction counts not biomass
Only accounted under waste sector when no energy is recovered
IPCC guidelines include a simple method It is good practice to disaggregate waste into waste
types and take into account burn-out efficiency of incinerator
5.77
Equation for carbon dioxide
CO2 emission (Gg/yr) = i(IWi*CCWi*FCFi*Efi*44/12)where i = MSW, HW, CW, SSMSW municipal solid waste, HW hazardous waste,
CW clinical waste and SS sewage sludge
IWi = Amount of incinerated waste type i
CCWi = Fraction of C content in waste type i
FCFi = Fraction of fossil C in waste type iEF = Burn-out efficiency of combustion of
incinerators for waste type i (fraction)
44/12 = Conversion from C to CO2
5.78
Equation for nitrous oxide
N2O emission (Gg/yr) = i(IWi*Efi)*10-6 where
IWi = Amount of incinerated waste type i (Gg/yr)
EFi = Aggregate emission factor for waste type i (kg N2O/Gg) or
N2O emission (Gg/yr) = i(IWi*ECi*FGVi)*10-9
IWi = Amount of incinerated waste type i (Gg/yr)
ECi = N2O emission concentration in flue gas from waste of type i (mg N2O /Mg)
FGVi = Flue gas volume by amount of incinerated waste type i (m3/Mg)
5.79
Emission factors and activity data for carbon dioxide
C content varies: sewage sludge, 30%; municipal solid waste, 40%; hazardous waste, 50%; and clinical waste, 60%.
It is assumed that there is very little <<virtually no>> fossil carbon in sewage sludge, 0%; high content in clinical and municipal, 40%; and very high content in hazardous waste, 90%
The efficiency of combustion is 95% for all waste streams, except hazardous, which is 99.5%
5.80
Emission factors and activity data for nitrous oxide
Emission factors differ with facility type and type of waste
Default factors can be used Consistency and comparability are difficult
due to heterogeneous waste types across countries
5.81
Reporting framework
5.82
General reporting recommendations
It is good practice to document and archive all information required to produce the national inventory estimates
See GPG2000, Chapter 8, Quality Assurance and Quality Control, Section 8.10.1, Internal Documentation and Archiving
Transparency in activity data and the possibility to retrace calculations are important
5.83
Report quality assurance/quality control Transparency can be improved through clear
documentation and explanations Estimate using different approaches Cross check emission factors Check default values, survey data and
secondary data preparation for activity data Cross check with other countries
Involve industry and government experts in review processes
5.84
Reporting for methane from solid waste disposal sites
If Tier 2 is applied, historical data and k values should be documented, and closed landfills should be accounted for
Distribution of waste (managed and unmanaged) for MCF should be documented
Comprehensive landfill coverage, including industrial, sludge disposal, construction and demolition waste sites is recommended
5.85
Reporting for methane from solid waste disposal sites
If methane recovery is reported an inventory is desirable. Flaring and energy recovery should be documented separately
Changes in parameters should be explained and referenced
Time series should apply the same methodology; if there are changes it is required to recalculate the entire time series to achieve consistency in trends (See GPG2000, Chapter 7, 7.3.2.2, Alternative recalculation techniques)
5.86
Reporting for methane from domestic waste-water handling
Function of human population and waste generation per person, expressed as biochemical oxygen demand
If in rural areas, only aerobical disposal; only urban population is accounted for
COD*2.5 = BOD Recalculate whole time series Calculations need to be retraced, particularly
if there are changes to MCFs
5.87
Reporting for methane from industrial waste-water handling
Industrial estimates are accepted if they are transparent and consistent with QA/QC
Recalculations need to be consistent over time
Default data for industrial waste water is in GPG2000, Chapter 5, Table 5.4
Sectoral tables and a detailed inventory report are necessary to provide transparency
5.88
Reporting nitrous oxide emissions from waste water
Based on IPCC Guidelines, Chapter 4, Agriculture, Section 4.8, Indirect N2O emissions from nitrogen used in agriculture
Future work on data, approaches and calculations is needed
5.89
Reporting for waste incineration
All waste incineration is to be included Avoid double counting with energy recovery,
even when waste is used as a substitute fuel (e.g. cement and brick production)
Default ranges for emission estimates are provided in GPG2000, Chapter 5, Tables 5.6 and 5.7
Support fuel, generally little, shall be reported in Energy sector; maybe important for hazardous waste
5.90
Key source category analysis and decision
trees
5.91
Comparison
5.92
Comparison betweenIPCC 1996GL and GPG2000
GPG2000 IPCC 1996GL - default approach
First Order Decay Method for Solid Waste Disposal Sites based on real- world conditions of decomposition
Based on last year’s waste entering the disposal sites. Good approximation only for long-term stable conditions. First Order Decay is mentioned without specific calculations
Includes a “check method” for countries with difficulties to calculate the emissions from domestic waste-water handling
Keeps a separation between: Domestic waste water Industrial waste water
Human sewage is indicated as an area for further development and no improvement over IPCC 1996GL is presented
Calculation made on the basis of an approximation developed for the Agriculture sector (see chapter on Agriculture sector)
New section including emissions from waste incineration covers: CO2 emissions N2O emissions
Contains no detailed methodologies <<correct?>>
5.93
Key activity data required for GPG2000 and IPCC 1996GL
GPG2000 IPCC 1996GL
Disposal activity for solid waste for several years
Less requirements with the check method for CH4 emissions from domestic waste
water Top-down modification of IPCC 1996GL
recommended due to high costs Incineration amounts, composition (carbon
content and fossil fraction) required for CO2
Emission measurements recommended for N2O
Disposal activity for current year, default values or a per capita approach
Waste-water flows and waste-water treatment data required
Very detailed, industry specific data required
No specific methodology
5.94
Key emission factors required for IPCC 1996GL and GPG2000
Most emission factors are common to both: Methane generation potential for
SWDS Human sewage conversion factor Methane conversion factor
New emission factors related to: Tier 2 for SWDS, particularly k value Waste incineration (lack of some default
values)
5.95
Link between IPCC 1996GL and GPG2000
GPG2000 uses the same tables as were provided in IPCC 1996GL, based on the same categories
5.96
List of problems
5.97
Problems addressed
Problems found by NAI experts in using IPCC 1996GL
Problems categorized into: Methodological issues Activity data (AD) Emission factors (EF)
GPG2000 addresses some deficiencies found in IPCC 1996GL
Strategies for improvement in methodology, AD and EF Strategy for AD and EF – tier approach Points to sources of data for AD and EF, including EFDB
5.98
Methodological issues Methodologies that are not covered :
Sludge spreading and composting, Use of burning under conditions not reflected
properly in the waste incineration section Tropical conditions of many NAI Parties vis-à-vis
methane generation Use of open dumps instead of landfills Lack of a proper calculation method for human
sewage in the case of island countries or countries with prevailing coastal populations, and complexity of the methodology.
5.99
Lack of waste methodologies that
reflect national circumstances
GPG2000 approach Improvement suggested
- The GPG2000 does not cover composting and sludge spreading, which are common practices in NAI countries
- Burning and open dump processes are not well covered by GPG2000 and are frequent practices in NAI countries.
- Initiate field studies to generate methodologies, or use approaches proposed by Annex 1 countries for these categories.
- Expand the proper sections to reflect the conditions prevailing in many NAI countries.
5.100
More deficiencies in the methodologies
GPG2000 approach Improvement suggested
- The GPG2000 does not cover conditions for tropical countries and management practices for both solid wastes and waste waters
- The approximation used in GPG2000 to calculate nitrous oxide from human sewage (the same approximation as in IPCC 1996GL) does not reflect properly the situation of coastal/island areas
- Initiate field studies to expand the methodology
- Adopt the proposed methodologies covered in the Agriculture chapter differentiating according to geographical reality
5.101
Complexity of methodology
GPG2000 approach Improvement suggested
- The methodologies presented for Solid Waste Disposal Sites and Waste Incineration require data that are not commonly available in NAI countries
- Methods similar to the Check method for waste water should be provided to enhance completeness of reporting
5.102
Activity data problems
Lack of data on generated solid waste
Lack of time-series data for waste generation
Lack of availability of disaggregated data
Lack of data on composition of solid waste
Lack of data on oxidation conditions
Extrapolations based on past data used to apply Tier 2 for Solid Waste Disposal Sites CH4 generation
Low reliability and high uncertainty of data
5.103
Emission factor problems
Inappropriate default values given in IPCC 1996GL
Default data not suitable for national circumstances
Lack of emission factors at disaggregated level
Lack of availability of methane conversion factors for certain NAI regions
Low reliability and high uncertainty of data
Lack of emission factors in IPCC 1996GL for waste incineration (covered by GPG 2000)
Default data commonly provides upper value, leading to overestimation
5.104
List of problems(Category wise)
5.105
CH4 Emissions from Solid Waste Disposal Sites
Table 6.A
5.106
Methodological issues
Use of open dumps or open incineration Recycling, commonly of wood and paper
but even of organic waste
5.107
Activity data and emission factors
Lack of activity data, both for the present and the required time series, for the waste flows and their composition
Default activity data for only 10 NAI countries Values reflected for k parameter for the application
of the First Order Decay method do not reflect tropical conditions of temperature and humidity. The higher k value in GPG2000 is 0.2 and the one in IPCC 1996GL is 0.4
The proposed Methane Correction Factor, even using the lesser value, 0.4, may lead to overestimations, due to shallowness and the frequent practice of burning as a pretreatment at disposal sites
5.108
Emissions from Wastewater Handling
Table 6.B
5.109
Methodological issues For CH4 emissions from domestic waste-water handling,
GPG2000 presents a simplified method called the “check method” avoiding the complexities in IPCC 1996GL
In NAI countries, national methods or parameters, or even activity data, may by available only infrequently
For CH4 emissions from industrial waste-water handling, GPG2000 presents a “best practice” for cases where these emissions represent a key source, recommending the selection of 3 or 4 key industries
For emissions of N2O from human sewage, no improvements were made in GPG2000 over IPPC 1996 GL. This methodology has several limitations that have caused several NAI countries to declare it “inapplicable”
5.110
Activity data and emission factors
Availability of activity data and emission factors is uncommon in NAI countries for CH4 emissions from domestic waste water, and the “check method” may help to overcome this issue. In any case, GPG 2000 is an improvement in that it identifies potential CH4 emissions
For CH4 emissions from industrial waste water, in cases where it is a key source, it is feasible to work only with the largest industries
For N2O emissions from human sewage, the activity data needed are relatively simple and easy to obtain
5.111
Emissions from Waste Incineration
Table 6.C
5.112
Methodological issues
This source category was only briefly introduced in the IPCC 1996GL, but is fully developed in the GPG2000
In NAI countries, incineration of waste (other than clinical waste) is uncommon due to high costs
Differentiation is made between CO2 and N2O because the former is calculated with a mass balance approach and the latter depends on operating conditions
5.113
Activity data and emission factors
GPG2000 recognizes the difficulties in finding activity data to differentiate the four proposed categories (municipal, hazardous, clinical and sewage sludge)
Do not request differentiation if data are not available when it is not a key source category
5.114
Review and assessment of activity data and
emission factors: data status and options
5.115
Status of EFDB for the Waste sector
EFDB is an emerging database All experts are expected to contribute to EFDB. Currently it contains only limited information on
Waste sector emission factors In future, with contributions from experts around
the world, EFDB should become a reliable source of data for emission factors for GHG inventory
5.116
EFDB – Waste sector status
IPCC 1996GL category Emission factor records
Solid Waste Disposal on Land (6A) 115
Wastewater Handling (6B) 191
Waste Incineration (6C) 47
Other (6D) 0
Total (as at October 2004) 353
5.117
Uncertainty estimation and reduction
5.118
Uncertainty estimation and reduction
The good practice approach requires that estimates of GHG inventories be accurate they should neither be over- nor underestimated
as far as can be judged Causes of uncertainty could include:
unidentified sources lack of data quality of data lack of transparency
5.119
Reporting uncertainties from solid waste disposal sites
Main uncertainty sources: Activity data (total municipal waste MSWT and
fraction sent to disposal sites MSWF) Emission factors (methane generation rate
constant) Other factors listed in GPG2000, Table 5.2:
Degradable organic carbon, fraction of degradable organic carbon, methane correction factor, fraction of methane in landfill gas
Possibly also methane recovery and oxidation factor
5.120
Reporting uncertainties from domestic waste-water handling
Uncertainties are related to BOD/person, maximum methane producing capacity and fraction treated anaerobically (data for population has little uncertainty (+5%))
Default ranges are: BOD/person and maximum methane
producing capacity (+ 30%) For fraction treated anaerobically use expert
judgement
5.121
Reporting uncertainties from industrial waste-water treatment
Uncertainties are related to industrial production, COD/unit waste water (from -50% to +100%), maximum methane producing capacity and fraction treated anaerobically
Default ranges are: industrial production (+ 25%) maximum methane producing capacity (+ 30%)
For fraction treated anaerobically use expert judgement
5.122
Reporting uncertainties from waste incineration
Activity data uncertainty on amount of incinerated waste assumed to be low (+5%) in developed countries. Some wastes, such as clinical waste, may be higher
Major uncertainty for CO2 is fossil carbon fraction
For N2O default values, uncertainty is as high as 100%