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CGE Greenhouse Gas Inventory Hands-on Training Workshop WASTE SECTOR

CGE Greenhouse Gas Inventory Hands-on Training Workshop WASTE SECTOR. 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 )

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CGE Greenhouse Gas Inventory Hands-on Training Workshop WASTE SECTOR

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  1. CGEGreenhouse Gas Inventory Hands-on Training WorkshopWASTE SECTOR

  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 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

  3. Introduction

  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 • Compilation 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. 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 cathegories, methodologies and decision trees

  6. Target groups • NAI inventory experts • National GHG inventory focal points

  7. NAI country examples • Analysis of national communications: Ethiopia, Ghana, Namibia, Nigeria, Morocco, South Africa and Uganda, • 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 category of CH4 emissions

  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.

  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.

  10. IPCC 1996GL andGPG2000 Approach and steps

  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)

  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

  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

  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

  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

  16. Characteristics of the methanogenic process • Highly heterogeneous • However, relevant factors to consider: • Waste management practices • Waste composition • Physical factors

  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

  18. Waste management practices (II) • Sanitary landfills • Specially designed • Gas and leakage control • Scale economy • Continued methane production

  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

  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

  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

  22. Methane emissions • Depend on several factors • Open dumps require other approaches • Availability and quality of relevant data

  23. Waste-water treatment • Produces methane, nitrous oxide and non-methane volatile organic compounds • May lead to storage of carbon through eutrophication

  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

  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)

  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

  27. Main industrial sources • Food processing: • Processing plants (fruit, sugar, meat, etc.) • Creameries • Breweries • Others • Pulp and paper

  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

  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

  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

  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

  32. Inventory preparation using IPCC 1996GL • Step 1: Conduct key 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 category 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 category analysis • Step 2:Select the categories

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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)

  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

  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

  47. GPG2000 Approach

  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

  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)

  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) = 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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