CGE Training Materials
National Greenhouse Gas Inventories
Energy Sector – Fuel Combustion
Version 2, April 2012
Consultative Group of Experts (CGE)
Training Materials for National Greenhouse Gas Inventories
Target Audience and Objective of the Training Materials
•
These training materials are suitable for people with beginner to intermediate level
knowledge of national greenhouse gas (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 energy sector
(fuel combustion);
b) Have a general understanding of the methods available, as well as of the main
challenges in that particular area;
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.
Consultative Group of Experts (CGE)
Training Materials for National Greenhouse Gas Inventories
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Acronyms
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EFDB
IPCC Emission Factor Database
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GPG
Good Practice Guidance
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GWP
Global Warming Potential
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IEA
International Energy Agency
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Training Materials for National Greenhouse Gas Inventories
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Outline of this Presentation – Fuel Combustion
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Fuel combustion
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References (slide 7)
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Basic steps for estimation of emissions (slide 23)
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Relationships with other sources and sectors (slide 41)
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Quality control and completeness (slide 43)
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Outline – Fuel Combustion
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Fugitive emissions
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Introduction
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Coal mining and handling
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Oil and natural gas systems
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Data issues
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References
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Training Materials for National Greenhouse Gas Inventories
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Survey
Audience poll…
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Who has prepared a national inventory for your country?
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Who has worked on the energy sector?
Please share…
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Problems you have faced in preparing estimates for the energy sector
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Your plans for the future to improve your inventory.
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Training Materials for National Greenhouse Gas Inventories
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1A.6
Reference Materials
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UNFCCC (COP decisions, reporting guidelines, etc.)
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IPCC
- Revised 1996 IPCC guidelines for national GHG inventories
- IPCC good practice guidance and uncertainty management in national GHG
inventories
- IPCC good practice guidance for land use, land-use change and forestry
- IPCC Emission Factor Database (EFDB)
- IPCC Working Group I Assessment Reports
- Use “old” Second Assessment Report (SAR) Global Warming Potential (GWP)
values for reporting
•
International Energy Agency (IEA)
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IPCC Guidance
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Fundamental methods laid out in the Revised 1996 IPCC Guidelines
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IPCC good practice guidance clarifies some issues (e.g. international bunker fuels) and
provides some updated factors…
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…but no major changes made for fuel combustion!
•
2006 IPCC Guidelines provide new information on non-energy use, new Tier 2 method
for oil systems fugitives, guidance on abandoned coal mines, etc.
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Training Materials for National Greenhouse Gas Inventories
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Key Category Analysis
• Level assessment based on share of total national emissions for each
source category.
• Trend assessment based on contribution of category to changes in
emission trends.
• Qualitative criteria
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Training Materials for National Greenhouse Gas Inventories
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Key Category Analysis (cont.)
• Idea of key sources based on a measure of which sources contribute to
uncertainty in inventory.
• Most, if not all, source categories in the energy sector will be key source
categories.
• The analysis only as good as the original emissions data.
• You probably already know your key categories.
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Fuel Combustion - Stationary Sources
• Energy industries
• Extraction, production and transformation
• Electricity generation, petroleum refining
• Autoproduction of electricity
• Manufacturing industries and construction
• Iron and steel production
• Non-ferrous metal production
• Chemical manufacturing
• Pulp, paper and print
• Food processing, beverages and tobacco
• Commercial/institutional
• Residential
• Agriculture/forestry/fisheries
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Example of Decision Tree
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Fuel Combustion - Autoproducers
Source: Revised 1996 IPCC Guidelines for national GHG inventories, Reference Manual – Volume 3, p. 1.32.
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Fuel Combustion - Mobile Sources
• Civil aviation
• Road transportation
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Cars
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Light duty trucks
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Heavy duty trucks and buses
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Motorcycles
• Railways
• Navigation
• International bunker fuels are reported separately.
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Carbon Dioxide (CO2) Emissions
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The calculation methodology is mass-balance-based.
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Oxidation of the carbon in fuels occurs during combustion.
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In perfect combustion conditions, total carbon content of fuels would be
converted to CO2.
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Real combustion processes result in small amounts of partially oxidized and
unoxidized carbon.
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Carbon Flow for a Typical Combustion Process
• Most carbon is emitted as CO2 immediately.
• A small fraction emitted as non-CO2 gases:
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CH4, CO, non-methane volatile organic compounds (NMVOCs)
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Ultimately oxidizes to CO2 in the atmosphere
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Integrated into overall calculation of CO2 emissions
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Each carbon atom has two atmospheric lifetimes
• The remaining part of the fuel carbon is unburnt:
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Assumed to remain as solid (ash and soot)
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Account by using oxidation factors.
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Non-CO2 Emissions
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Direct greenhouse gases:
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Methane (CH4)
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Nitrous oxide (N2O).
Precursors and SO2:
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Nitrogen oxides (NOx)
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Carbon monoxide (CO)
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Non-methane volatile organic compounds (NMVOCs)
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Sulphur dioxide (SO2).
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Non-CO2 Emissions Require Detailed Process Information
• Combustion conditions
• Size and vintage of the combustion technology
• Maintenance
• Operational practices
• Emission controls
• Fuel characteristics.
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Methane (CH4)
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Emissions are a function of:
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methane content of the fuel
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hydrocarbons passing unburned through engine
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engine type
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post-combustion controls.
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Depends on temperature in boiler/kiln/stove.
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Highest emissions are in residential applications (e.g. small stoves, open biomass
burning, charcoal production).
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Nitrous Oxide (N2O)
• Lower combustion temperatures tend to lead to higher N2O emissions.
• Emission controls (catalysts) on vehicles can increase the rate of N2O generation,
depending on:
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driving practices (i.e. number of cold starts)
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type and age of the catalyst.
• Significant emissions for countries with a high penetration of vehicles with
catalysts:
http://unfccc.int/resource/docs/2004/sbsta/inf03.pdf
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Methods for Estimating CO2
• Reference approach (Tier 1):
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Estimates based on national energy balance (production + imports - exports)
by fuel type without information on activities
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Performed quickly if basic energy balance sheet is available
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Way of cross-checking emission estimates of CO2 with the sectoral approach.
• Sectoral approach (Tier 1):
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Estimates based on fuel consumption data by sectoral activity.
• Bottom-up approaches (Tier 2 or 3):
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More detailed activity and fuel data are required.
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Training Materials for National Greenhouse Gas Inventories
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Emissions by Source Categories - Fundamental Equation
Source: Revised 1996 IPCC Guidelines for national GHG inventories, Reference Manual – Volume 3, p. 1.30.
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Six Basic Steps for Estimating CO2
1.
Collect fuel consumption data.
2.
Convert fuel data to a common energy unit.
3.
Select carbon content factors for each fossil fuel/product type and estimate the
total carbon content of fuels consumed.
4.
Subtract the amount of carbon stored in products for long periods of time.
5.
Multiply by an oxidation factor.
6.
Convert carbon to full molecular weight of CO2 and sum across all fuels.
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Step 1. Collect Consumption Data
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Reference approach
- Estimate apparent consumption of fuels within the country.
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Sectoral approach
- Collect actual consumption statistics by fuel type and economic sector.
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Tier 2 or 3
- Collect actual fuel consumption statistics by fuel type, economic sector
and combustion technology type.
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Training Materials for National Greenhouse Gas Inventories
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Step 1. Collect Consumption Data - Data Collection Issues
• IPCC sectoral approach can still be used even if energy data are not collected
using the same sector categories:
- Focus on completeness and use judgement or proxy data to allocate to
various subsectors.
• Biomass combustion data are not needed for CO2 estimation, but are reported
for information purposes.
• Informal sector fuel use is an important issue if not captured in energy statistics:
- Household kerosene use can be approximated based on expert judgement
or proxy data.
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Step 2. Common Energy Unit
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Convert :
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Fuel data into a common energy unit
o
Production and consumption of solid and liquid fuels in tonnes
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Gaseous fuels in cubic metres
o
Original units into energy units using calorific values (i.e. heating values).
Reference approach: use different calorific values for production, imports and
exports.
•
Calorific values used should be reported.
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Step 3. Estimate Total Carbon Content of Fuels Consumed
Natural gas
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Depends on composition (methane, ethane, propane, butane and heavier
hydrocarbons)
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Natural gas flared at the production site will usually be “wet’’ – its carbon
content factor will be different
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Typical: 15 to 17 tonnes C/TJ.
Oil
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•
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Coal
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Lower carbon content for light refined petroleum products such as gasoline
Higher for heavier products such as residual fuel oil
Typical for crude oil: 20 tonnes C/TJ.
Depend on coal's rank and composition of hydrogen, sulphur, ash, oxygen
and nitrogen
Typical ranges: from 25 to 28 tonnes C/TJ.
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Step 4. Subtract Non-Energy Uses
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•
•
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Oil refineries: asphalt and bitumen for road construction, naphthas,
lubricants and plastics
Natural gas: for ammonia production
Liquid Petroleum Gas (LPG): solvents and synthetic rubber
Coking: metals industry.
• Attempt to use country-specific data instead of IPCC default carbon storage
factors.
Source: Revised 1996 IPCC Guidelines for national GHG inventories, Reference Manual – Volume 3, p. 1.26.
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Step 5. Multiply by an Oxidation Factor
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Multiply by an oxidation factor to
account for the small amount of
unoxidized carbon that is left in
ash or soot.
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Amount of carbon remaining
unoxidized should be low for oil
and natural gas combustion…
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…but can be larger and more
variable for coal combustion.
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When national oxidation factors
are not available, use IPCC
default factors.
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Step 5. (Cont.) - Oxidation Factor Values
Natural gas
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Less than 1% left unburned
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Remains as soot in the burner, stack or environment
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IPCC default oxidation factor = 99.5%
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Higher for flares in the oil and gas industry
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Closer to 100% for efficient turbines.
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1.5 ± 1 per cent left unburned
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IPCC default oxidation factor = 99%
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Recent research has shown 100% in autos.
Oil
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Step 5. (Cont.) - Oxidation Factor Values
Coal
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Range from 0.6% to 6.6% unburned
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Primarily in the form of bottom and fly ash
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IPCC default oxidation factor = 98%.
Biomass
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Can range widely, especially for open combustion
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For closed combustion (e.g. boiler), the range is from 1% to 10%
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No IPCC default.
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Step 6. Convert to Full Molecular Weight and Sum
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Convert carbon to full molecular weight of CO2 and sum across all fuels.
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To express the results as CO2, multiply the quantity of carbon oxidized by the
molecular weight ratio of CO2 to C (44:12).
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Step 6. (Cont.) - International Bunker Fuels
• CO2 emissions arising from fuels used in ships or aircraft for international
transport, not to be included in the national total.
• Fuels delivered to and consumed by international bunkers should be
subtracted from the fuel supply to the country.
• Bunker fuel emissions should be mentioned in a separate table as a memo item.
• See IPCC decision trees on marine and aviation transport emission allocation.
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Step 6. (Cont.) - Biomass Fuels
• CO2 emissions from biomass fuels should not be included in national emission
totals from fuel combustion.
• Reported for information only…
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Household fuelwood
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Ethanol and biodiesel for transport.
• Account for mixed fuels (e.g. ethanol blends).
• Net CO2 emissions implicitly accounted for under the LULUCF sector
• Non-CO2 emissions from biomass combustion should be estimated and reported
under the energy sector!
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Methods for Non-CO2 Emissions
Tier 1
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Multiply fuel consumed by an average emission factor:
• Does not require detailed activity data
• Rely on widely available fuel supply data that assume an average
combustion technology is used.
Tiers 2/3
• Multiply fuel consumed by detailed fuel type and technology-specific
emission factors:
• Tier 2 methods use data that are disaggregated according to
technology types
• Tier 3 methods estimate emissions according to activity types (km
travelled or tonnes-km carried) and specific fuel efficiency or fuel
rates.
Use the most disaggregated technology-specific and country-specific
emission factors available.
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Training Materials for National Greenhouse Gas Inventories
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Fundamental Equation
Emissions =
Σ(Emission Factorabc • Fuel Consumptionabc)
Where,
a = fuel type
b = sector activity
c = technology type including emissions controls.
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Stationary Combustion
• Default emission factors for CH4, N2O, NOx, CO and NMVOCs by major
technology and fuel type are presented in the IPCC Guidelines.
• Most notable: CH4 emissions from open burning and biomass combustion.
• Charcoal production is likely to produce methane emissions at a rate that is
several orders of magnitude greater than from other combustion processes.
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Mobile Combustion
• Major transport activity (road, air, rail and ships).
• Most notable: N2O emissions from road transportation, affected by the type of
emission control technologies.
• Non-Annex I Parties should focus their efforts on collecting data on the number of
vehicles with catalytic emissions control devices that operate in their country.
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Mobile Combustion (cont.)
Road transport activity data:
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Assume vast majority of motor gasoline used for transport
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Check data with equipment counts or vehicle sales/import/export data
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Base assumptions of vehicle type and emission control technology on vehicle
vintage data (i.e. model year of sale) and assumed activity level (i.e. vehicle-
km-travelled/vehicle)
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Consider national emission standards, leaded gasoline prevalence, and
compliance with standards.
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Example of Decision Tree
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Relationships with Other Sources and Sectors
Industrial processes sector:
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Non-energy fossil fuel feedstocks data, if available, may not be reliable
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Petrochemical “feedstocks” may actually be used for energy
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Coal purchased by iron and steel industry may be used to make coke
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Focus on petrochemical industry and metal production (e.g. iron and steel)
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Conservative estimate: assume plastics, asphalt, and some lubricants
stored
•
Subtract carbon content from these products.
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Training Materials for National Greenhouse Gas Inventories
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Relationships with Other Sources and Sectors (cont.)
Waste sector:
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Combustion of wastes for energy purposes included in energy sector
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Incineration of plastics.
LULUCF sector:
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Biomass carbon implicitly accounted for.
Autoproduction of electricity
Fuel use for military purposes
Mobile sources in agriculture
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Quality Control and Completeness Checks
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All gases (CO2, CH4 and N2O)
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All source and subsource categories
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All national territories addressed
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Bunker fuels and military operations
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All fossil-fuel-fired electric power stations
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Blast furnaces and coke production
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Waste combustion with energy recovery
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Black market fuels
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Non-metered fuel use for pipelines by compressor stations.
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Uncertainty
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Uncertainty in carbon content and calorific values for fuels is related to the
variability in fuel composition and frequency of actual
measurements. Likely to be small for all countries.
•
For most non-Annex I Parties the uncertainty in activity data (i.e. fuel
consumption data) will be the dominant issue!
- Effort should focus on collection of fuel consumption data
- Country-specific carbon content factors are unlikely to improve CO2
estimates significantly.
•
It is important to document the likely causes of uncertainty and discuss
steps taken to reduce uncertainties.
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Thank you
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