1

CGE Greenhouse Gas Inventory Hands-on Training Workshop

for the African Region

- Energy Sector –Combustion

Pretoria, South Africa18-22 September 2006

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Outline of Course Fuel combustion (Today)

References Basic Emission Processes Methodologies Relationships with other sources and sectors Uncertainty Quality control and completeness

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Outline of Course (continued)

Fugitives (Tomorrow) References Coal mining and handling Oil and natural gas systems Data issues

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Survey says…?

Audience poll… Who has prepared a national inventory for

your country? Who has worked on the Energy Sector?

Please share your… Problems you have faced with preparing

estimates for the Energy Sector Plans for the future to improve your inventory

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Reference materials UNFCCC (COP decisions, reporting

guidelines, etc.) IPCC

Revised 1996 IPCC Guidelines Good Practice Guidance Emission Factor Database (EFDB) IPCC WG I Assessment Reports

Use “old” SAR GWP values for reporting International Energy Agency

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IPCC Guidance Fundamental methods laid out in 1996 Revised

Guidelines IPCC Good Practice clarifies some issues (e.g.,

international bunker fuels) and provides some updated factors…

…but no significant changes made for fuel combustion!

2006 IPCC Guidelines provides new information on Non-Energy Use, new Tier 2 method for oil systems fugitives, & guidance on abandoned coal mines

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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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Key Category Analysis 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

Analysis only as good as original emissions data.

You probably already know your key categories.

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Energy SectorFuel Combustion

Emissions

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African GHG Emissions (Top 20)

0

50

100

150

200

250

300

350

400

450S

outh

Afri

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Nig

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Con

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.R.

Zam

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Egy

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Sud

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Ivoi

re

Mad

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car

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babw

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Tanz

ania

Eth

iopi

a

Uga

nda

Ken

ya

Liby

a

Mor

occo

Ang

ola

Gha

na

Ben

in

Libe

ria

Tg C

O2-

eq.

Total Emissions

Energy Emissions

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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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Autoproducers

Note: p. 1.32 of the IPCC Guidelines, Reference Manual - Volume 3

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Mobile Sources Civil Aviation Road Transportation

Cars Light duty trucks Heavy duty trucks and buses Motorcycles

Railways Navigation

International Bunker Fuels are reported separately

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Carbon dioxide (CO2) emissions

Methodology is mass balance-based Oxidation of the carbon in fuels during

combustion In perfect combustion conditions, total

carbon content of fuels would be converted to CO2

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 Small fraction emitted as non-CO2 gases

CH4, CO, NMVOCs Ultimately oxidizes to CO2 in the atmosphere Integrated into overall calculation of CO2

emissions Remaining part of the fuel carbon is unburned

Assumed to remain as solid (ash and soot) Account by using oxidation factors

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Non-CO2 emissions Direct greenhouse gases

Methane (CH4) Nitrous oxide (N2O)

Precursors and SO2

Nitrogen oxides (NOx) Carbon monoxide (CO) Non-methane volatile organic compounds

(NMVOCs) Sulfur dioxide (SO2)

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Non-CO2 requires 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) Emissions a function of:

methane content of the fuel hydrocarbons passing unburnt through engine engine type post-combustion controls

Depends on temperature in boiler/kiln/stove Highest emissions 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:

driving practices (i.e., number of cold starts) 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 CO2

‘Reference Approach’ (Tier 1) estimates based on national energy balance (production +

imports - exports) by fuel type without information on activities

performed quickly if basic energy balance sheet is available way of cross-checking emission estimates of CO2 with the

Sectoral Approach ‘Sectoral Approach’ (Tier 1)

Estimates based on fuel consumption data by sectoral activity

‘Bottom-Up Approaches’ (Tier 2 or 3) More detailed activity and fuel data

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Fundamental Equation

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Six basic steps1. Collect fuel consumption data2. Convert fuel data to a common energy unit3. 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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1. Consumption Data Reference Approach:

Estimate apparent consumption of fuels within the country

Sectoral Approach: Collect actual consumption statistics by fuel

type and economic sector Tier 2 or 3:

Collect actual fuel consumption statistics by fuel type, economic sector, and combustion technology type

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Data Collection Issues IPCC sectoral approach can still be used even

if energy data are not collected using same sector categories focus on completeness and use judgment or

proxy data to allocate to various subsectors Biomass combustion not needed for CO2, but

reported for information purposes Informal sector fuel use is important issue if not

captured in energy statistics household kerosene use can be approximated

based on expert judgment or proxy data

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2. Common Energy Unit Convert fuel data to a common energy unit Production and consumption of solid and

liquid fuels in tons Gaseous fuels in cubic meters Original units converted 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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3. Estimate total carbon content of fuels consumed

Natural Gas Depends on composition (methane, ethane, propane,

butane, and heavier hydrocarbons) Natural gas flared at the production site will usually be "wet“ -

its carbon content factor will be different Typical: 15 to 17 tons C/TJ

Oil Lower carbon content for light refined petroleum products

such as gasoline Higher for heavier products such as residual fuel oil Typical for crude oil is 20 ton C/TJ

Coal Depend on coal's rank and composition of hydrogen, sulfur,

ash, oxygen, and nitrogen Typical ranges from 25 to 28 ton C/TJ

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4. Subtract non-energy uses 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 industryAttempt to use country-specific data instead of IPCC default

carbon storage factors.

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5. Oxidation Factor Multiply by an oxidation factor

to account for the small amount of unoxidized carbon that is left in ash or soot.

Amount of carbon remaining unoxidized should be low for oil and natural gas combustion…

…but can be larger and more variable for coal combustion

When national oxidation factors are not available, use IPCC default factors

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Oxidation Factor ValuesNatural Gas

Less than 1 percent left unburned Remains as soot in the burner, stack, or

environment IPCC default oxidation factor = 99.5% Higher for flares in the oil and gas industry Closer to 100% for efficient turbines

Oil 1.5 ± 1 percent left unburned IPCC default oxidation factor = 99% Recent research has shown 100% in autos

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Coal Range from 0.6 to 6.6 percent unburned Primarily in the form of bottom and fly ash IPCC default oxidation factor = 98%

Biomass Can range widely, especially for open

combustion For closed combustion (e.g., boiler) range

from 1 to 10 percent No IPCC default

Oxidation Factor Values (cont.)

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6. Convert to full molecular weight and sum

Convert carbon to full molecular weight of CO2 and summation across all fuels

To express the results as carbon dioxide (CO2), multiply the quantity of carbon oxidized by the molecular weight ratio of CO2 to C (44:12)

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International Bunker Fuels CO2 emissions arising from fuels used in

ships or aircraft for international transport not 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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Biomass Fuels CO2 emissions should not be included in national

emission totals from fuel combustion Reported for information only…

household fuelwood ethanol & biodiesel for transport

Account for mixed fuels (e.g., ethanol blends) Net CO2 emissions implicitly accounted for under the

Land Use Change and Forestry 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 Multiply fuel consumed by an average emission factor Do 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 is disaggregated according to

technology types Tier 3 methods estimate emissions according to activity types

(km traveled or ton-km carried) and specific fuel efficiency or fuel rates

Use most disaggregated technology-specific and country-specific emission factors available

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Fundamental EquationEmissions =

Σ(Emission Factorabc • Fuel Consumptionabc)

Where,a = fuel typeb = sector activityc = technology type including emissions controls

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Stationary Combustion Default emission factors for CH4, N2O, NOx,

CO, & NMVOCs by major technology and fuel types 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 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 countries 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 assume vast majority of motor gasoline used for

transport Check data with equipment counts or vehicle

sales/import/export data 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., vkt/vehicle)

Consider national emission standards, leaded gasoline prevalence, and compliance with standards

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Relationships with Other Sources and Sectors

Industrial Processes Sector non-energy fossil fuel feedstocks data, if

available, may not be reliable petrochemical “feedstocks” may actually be

used for energy coal purchased by iron and steel industry

may be used to make coke focus on petrochemical industry and metal

production (e.g., iron and steel) conservative estimate: Assume plastics,

asphalt, and some lubricants stored subtract carbon content from these products

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Relationships with Other Sources and Sectors (cont.)

Waste Sector combustion of wastes for energy purposes

included in Energy Sector incineration of plastics

Land-Use Change and Forestry Sector 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

All gases (CO2, CH4, and N2O) All source and sub-source categories All national territories addressed Bunker fuels and military operations All fossil fuel fired electric power stations Blast furnaces and coke production Waste combustion with energy recovery Black market fuels Non-metered fuel use for pipelines by

compressor stations

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Uncertainty 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 countries, the uncertainty in activity data (i.e., fuel consumption data) will 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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IPCC Software and reporting tables

Software to aid in preparation of greenhouse gas inventories

Provides IPCC default (i.e., Tier 1) methods National factors can be used where

available