Transcript Presentation

CGE Training Materials
National Greenhouse Gas
Inventories
Waste Sector
Version 2, April 2012
Consultative Group of Experts (CGE)
Training Materials for National Greenhouse Gas Inventories
Target Audience and Objective from Training Materials
• These training materials are suitable for people with beginner to intermediate level
knowledge of national greenhouse (GHG) inventory development.
• After having read this Presentation, in combination with the related documentation,
the reader should:
a) Have an overview of how emissions inventories are developed for the waste
sector;
b) Have a general understanding of the UNFCCC and IPCC guidelines;
c) Be able to determine which methods suits their country’s situation best;
d) know where to find more detailed information on the topic discussed.
• These training materials have been developed primarily on the basis of
methodologies developed by the IPCC; hence the reader is always encouraged
to refer to the original documents to obtain further detailed information on a
particular issue.
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Acronyms
•
BOD
Biochemical oxygen demand
•
DOC
Degradable Organic Carbon
•
EFDB
IPCC Emission Factor Database
•
GHG
Greenhouse Gas
•
GPG
Good Practice Guidance
•
MSW
Municipal Solid Waste
•
SWDS
Solid Waste Disposal Site
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Outline of course – Waste Sector
• Introduction (slide 5)
• Definitions (slide 7)
• Revised 1996 IPCC Guidelines (slide 29)
• Good Practice Guidance and Uncertainty Management in National Greenhouse
Gas Inventories (slide 46)
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Introduction
• GHG inventories for the biological sectors, such as waste, are characterized by:
•
Methodological limitations
•
Lack of data or low reliability of existing data
•
High uncertainty.
• This presentation aims to assist non-Annex I (NAI) Parties in preparing GHG
inventories using the Revised 1996 IPCC Guidelines, particularly in the context of
UNFCCC decision 17/CP.8, focusing on:
•
The need to shift to the IPCC good practice guidance (2000) and higher
tiers/methods to reduce uncertainty
•
Complete overview of the tools and methods
•
Use of UNFCCC inventory software and EFDB
•
Review of activity data and emission factors and options to reduce uncertainty
•
Use of key sources, methodologies and decision trees.
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NAI Party examples
• Examination of national communications
• 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.
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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.
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Definitions (cont.)
• 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.
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Revised 1996 IPCC
Guidelines and
IPCC good practice guidance
(2000)
Approach and steps
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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).
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Decomposition of Waste
• Anaerobic decomposition of man-made waste by methanogenic bacteria
a) Solid waste
• Land disposal sites
b) Liquid waste
• Human sewage
• Industrial waste water.
• Nitrous oxide emissions from waste-water are also produced from protein
decomposition.
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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.
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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.
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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.
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Characteristics of the Methanogenic Process
• Highly heterogeneous
• However, relevant factors to consider:
•
Waste management practices
•
Waste composition
•
Physical factors.
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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.
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Waste Management Practices (cont.)
Sanitary landfills
•
Specially designed
•
Gas and leakage control
•
Scale economy
•
Continued methane production.
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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.
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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.
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Physical Factors (cont.)
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.
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Methane Emissions
• Depend on several factors
• Open dumps require other approaches
• Availability and quality of relevant data.
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Wastewater Treatment
• Produces methane, nitrous oxide and non-methane volatile organic compounds
• May lead to storage of carbon through eutrophication.
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Methane Emissions from Wastewater 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.
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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).
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Biochemical Oxygen Demand
• Is the organic content of wastewater (“loading”)
• Represents oxygen 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.
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Main Industrial Sources
• Food processing:
•
Processing plants (fruit, sugar, meat, etc.)
•
Creameries
•
Breweries
•
Others.
• Pulp and paper.
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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.
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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.
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Revised 1996 IPCC Guidelines
• 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.
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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.
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Inventory Preparation using Revised 1996 IPCC Guidelines
• Step 1: Conduct key source category analysis for waste sector where:
a) Sector is compared to other source sectors such as energy, agriculture,
LULUCF, etc.
b) Estimate waste sector’s share of national GHG inventory
c) Key source sector identification adopted by Parties that have already
prepared an initial national communication, have inventory estimates
d) Parties that have not prepared an initial national communication can use
inventories prepared under other programmes/projects
e) Parties that have not prepared any inventory, may not be able to carry out
the key source sector analysis.
• Step 2: Select the categories
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Inventory Preparation using Revised 1996 IPCC Guidelines (cont.)
• 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.
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Calculation of Methane from Solid Waste Disposal
• For sanitary landfills there are several methods:
a) Mass balance and theoretical gas yield
b) Theoretical first order kinetics methodologies
c) Regression approach.
• Complex models not applicable for regions or countries.
• Open dumps considered to emit 50%, but should be reported separately.
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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:
a) Using empirical formulae
b) Using degradable organic content.
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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.
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Using Degradable Organic Content (Basis for Tier 1)
• Calculated from the weighted average of the carbon content of various components
of the waste stream
• Requires knowledge of:
a) Carbon content of the fractions
b) Composition of the fractions in the waste stream
• This method is the basis for the Tier I calculation approach.
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Equation
• Methane emissions =
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
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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.
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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
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Limitations
• Main:
a) No time factor
b) 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.
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Default Method – Tier 1
a) 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
b) The former DOC dissimilated was reduced from 0.77 to 0.5 – 0.6, due to the
presence of lignin.
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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.
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Default method – Tier 1 good practice example
• 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)
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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
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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 (GDP) as an indicator of waste production rates.
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IPCC Good Practice
Guidance Approach
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Theoretical First Order Kinetics Methodologies (Tier 2)
• Tier 2 considers the long period of time involved in organic matter decomposition
and methane generation.
• Main factors:
a) Waste generation and composition
b) Environmental variables (moisture content, pH, temperature and available
nutrients)
c) Age, type and time since closure of landfill.
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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)
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Good Practice Equation
• Time t is replaced by t-x, a 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) = Sx [(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).
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Good Practice Equation (cont.)
• 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
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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.
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Methane Generation Rate Constant
• Is determined by type of waste and conditions
• Measurements range from 0.03 to 0.2 per year, equivalent to half lives from 23 to
3 years
• The more degradable material and humidity, the lower the half life
• Default value: 0.05 per year, or a half life of 14 years.
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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
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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)
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Practical Applications
• Base for Tier 2 approach
• Applied earlier in:
a) United Kingdom
b) The Netherlands
c) Canada.
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Regression Approach
• From empirical models
• Statistical and regressional analysis applied.
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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?
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Calculations of Emissions from Wastewater 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.
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Methane from Domestic and Commercial Wastewater
• Simplified approach
• Data:
a) BOD in Gg per 1000 persons (default values)
b) Country population in thousands
c) Fraction of total waste water treated anaerobically (0.1–0.15 as default)
d) Methane emission factor
(default 0.22 Gg CH4/Gg BOD
e) Subtract recovered methane.
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Equation
• Methane emission =
Population (103) x Gg BOD5/1000 persons x Fraction anaerobically
treated x 0.22 Gg CH4/Gg BOD – Methane recovered
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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
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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
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Check Method Rationale
• Emission factor is expressed in BOD; however COD is used for many purposes
• 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).
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Methane Conversion Factor
• IPCC guidelines recommends separate calculations for wastewater and sludge.
This influences the detailed approach calculation.
• Apart from 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.
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Detailed Approach
• Considers two additional factors:
a) Different treatment methods used and total waste water treated using each method
b) MCF for each treatment.
• The final result is the sum of the fractions calculated by the simplified approach, less
the recovered methane.
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Equation
• Domestic and commercial waste-water emissions =
(Si Methane calculated by simplified approach x
Fraction waste water treated using method i x MCF for method i)
- methane recovered
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Methane Emissions from Industrial Wastewater
• Industrial wastewater 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 wastewater loading
• Most estimates used are for point sources
• Focus on key industries is required and default values are provided.
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Emissions from Industrial Wastewater Treatment
• Simplified approach:
• Determine relevant industries (wine, beer, food, paper, etc.)
• Estimate wastewater 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.
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Equation
• Industrial wastewater emissions =
(Si wastewater outflow by industry (Ml/yr) x kg BOD5/I
x Fraction wastewater treated anaerobically x 0.22) - Methane recovered
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Detailed Approach
• Similar to the approach used for estimating methane emissions from domestic and
commercial wastewater.
• Requires knowledge of:
a) Specific wastewater treatments
b) MCF for each factor.
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Equation
• Industrial wastewater Emissions =
(Si Wastewater outflow by industry (Ml/yr) x kg BOD5/l x
Fraction wastewater treated using method i x MCF for method i)
- Methane recovered
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Uncertainties in Calculations
a) Lack of information about volumes, treatments and recycling
b) Discharge into surface waters:
• Not anaerobic (default 0%)
• Anaerobic (default 50%)
c) Septic tanks (long retention times: more than 6 months)
• Long retention of solids (default 50%)
• Short retention of solids (default 10%)
d) Open pits and latrines (default 20%)
e) Other limitations: BOD, temperature, pH and retention time.
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Emissions from Waste Incineration
• For carbon dioxide, only fossil fraction counts, not biomass
• Only accounted under waste sector when no energy is recovered
• IPCC good practice guidance include a simple method
a) It is good practice to disaggregate waste into waste types and take into
account burn-out efficiency of incinerator.
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Equation for Carbon Dioxide
CO2 emission (Gg/yr) = Si(IWi*CCWi*FCFi*Efi*44/12)
Where:
i = MSW, HW, CW, SS
MSW municipal solid waste, HW hazardous waste, CW clinical waste and SS
sewage sludge
IWi = Amount of incinerated waste type i
CCWi = Fraction of carbon content in waste type i
FCFi = Fraction of fossil carbon in waste type i
EF = Burn-out efficiency of combustion of incinerators for waste type i (fraction)
44/12 = Conversion from carbon to CO2
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Equation for Nitrous Oxide
N2O emission (Gg/yr) = Si(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) = Si(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 N 2O /Mg)
FGVi = Flue gas volume by amount of incinerated waste type i (m 3/Mg)
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Emission Factors and Activity Data for Carbon Dioxide
•
Carbon 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%.
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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.
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Reporting Framework: General 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.
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Report Quality Assurance/Quality Control
• Transparency can be improved through clear documentation and explanations:
a) Estimate using different approaches
b) Cross-check emission factors
c) Check default values, survey data and secondary data preparation for activity
data
d) Cross-check with other countries.
• Involve industry and government experts in review processes.
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Reporting for Methane from Solid Waste Disposal Sites
a) If Tier 2 is applied, historical data and k values should be documented, and
closed landfills should be accounted for
b) Distribution of waste (managed and unmanaged) for MCF should be
documented
c) Comprehensive landfill coverage, including industrial, sludge disposal,
construction and demolition waste sites is recommended.
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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).
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Reporting for Methane from Domestic Wastewater 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.
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Reporting for Methane from Industrial Wastewater Handling (cont.)
•
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.
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Reporting Nitrous Oxide Emissions from Wastewater
• Based on the Revised 1996 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.
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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 the energy sector; may be
important for hazardous waste.
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Comparison Between Revised 1996 IPCC Guidelines and IPCC Good
Practice Guidance
IPCC good practice guidance
Revised 1996 IPCC Guidelines - default approach
First Order Decay Method for Solid Waste Disposal Sites based on real-world
Based on last year’s waste entering the disposal sites. Good approximation only for
conditions of decomposition
long-term stable conditions. First Order Decay is mentioned without specific
calculations
Includes a “check method” for countries with difficulties to calculate the
Keeps a separation between:
emissions from domestic waste-water handling
 Domestic waste water
 Industrial waste water
Human sewage is indicated as an area for further development and no
Calculation made on the basis of an approximation developed for the Agriculture
improvement over IPCC 1996GL is presented
sector (see chapter on Agriculture sector)
New section including emissions from waste incineration covers:
Contains no detailed methodologies
 CO2 emissions
 N2O emissions
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Comparison of Key Activity Data Required
IPCC good practice guidance

Disposal activity for solid waste for several years

Less requirements with the check method for CH4 emissions from domestic
Revised 1996 IPCC Guidelines

Disposal activity for current year, default values or a per capita
approach
waste water

Waste-water flows and waste-water treatment data required

Top-down modification of IPCC 1996GL recommended due to high costs

Very detailed, industry specific data required

Incineration amounts, composition (carbon content and fossil fraction) required

No specific methodology
for CO2

Emission measurements recommended for N2O
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Comparison of Key Emission Factors Required
Most emission factors are common to both IPCC 1996 GL and GPG 2000:
•
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).
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Link Between IPCC 1996 GL and GPG 2000
• GPG 2000 uses the same tables as were provided in IPCC 1996GL, based
on the same categories.
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Problems Addressed
• Problems found by NAI experts when using IPCC 1996 GL
• Problems categorized into:
•
Methodological issues
•
Activity data
•
Emission factors.
• GPG2000 addresses some deficiencies found in IPCC 1996 GL:
•
Strategies for improvement in methodology, activity data and emission factors
•
Strategy for activity data and emission factors – tier approach
•
Sources of data for activity data and emission factors, including EFDB.
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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.
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Lack of Waste Methodologies that Reflect National Circumstances
IPCC good practice guidance approach
-
-
The GPG 2000 does not cover composting and sludge spreading, which
Improvement suggested
-
Initiate field studies to generate methodologies, or use
are common practices in NAI countries
approaches proposed by Annex I countries for these
Burning and open dump processes are not well covered by GPG 2000 and
categories.
are frequent practices in NAI countries.
-
Expand the proper sections to reflect the conditions
prevailing in many NAI countries.
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More Deficiencies in the Methodologies
IPCC good practice guidance approach
-
-
Improvement suggested
The GPG 2000 does not cover conditions for tropical countries and management practices for
-
Initiate field studies to expand the methodology
both solid wastes and wastewaters
-
Adopt the proposed methodologies covered in the agriculture
The approximation used in GPG 2000 to calculate nitrous oxide from human sewage (the
chapter differentiating according to geographical reality
same approximation as in IPCC 1996 GL) does not reflect properly the situation of
coastal/island areas
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Complexity of Methodology
IPCC good practice guidance approach
-
The methodologies presented for Solid Waste Disposal Sites and Waste
Incineration require data that are not commonly available in NAI countries
Improvement suggested
-
Methods similar to the Check method for waste water should be provided to
enhance completeness of reporting
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Activity Data Problems
•
•
•
•
•
•
Inadequate data on generated solid waste
Inadequate time-series data for waste generation
Non-availability of disaggregated data
Inadequate data on composition of solid waste
Inadequate 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
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Emission Factor Problems
• Inappropriate default values given in IPCC 1996 GL
• 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 1996 GL for waste incineration (covered
by GPG 2000)
• Default data commonly provides upper value, leading to overestimation
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List of problems,by category
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CH4 Emissions from Solid Waste Disposal Sites, Table 6.A
Methodological issues:
•
Use of open dumps or open incineration
•
Recycling, commonly of wood and paper but even of organic waste.
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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
GPG 2000 is 0.2 and the one in IPCC 1996 GL 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.
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Emissions from Wastewater Handling, Table 6.B
Methodological issues
• For CH4 emissions from domestic wastewater handling, GPG2000 presents a simplified
method called the “check method” avoiding the complexities in IPCC 1996 GL.
• 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”.
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Activity Data and Emission Factors
• Availability of activity data and emission factors is uncommon in NAI countries for
CH4 emissions from domestic wastewater, 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.
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Emissions from Waste Incineration, Table 6.C
Methodological issues
• This source category was only briefly introduced in the IPCC 1996GL, but is fully developed
in GPG 2000.
• 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.
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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.
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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 .
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Reporting Uncertainties from 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.
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Uncertainty Estimation and Reduction
• 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.
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Reporting Uncertainties from Industrial Wastewater Treatment
• Uncertainties are related to industrial production, COD/unit wastewater (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.
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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%.
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Thank you!
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