CGE Training Materials National Greenhouse Gas Inventories Energy Sector – Fuel Combustion

CGE Training Materials

National Greenhouse Gas Inventories

Energy Sector – Fuel Combustion

Version 2, April 2012

Training Materials for National Greenhouse Gas Inventories

Consultative Group of Experts (CGE)

Target Audience and Objective of the Training Materials

2

• 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.



Acronyms

• EFDB IPCC Emission Factor Database

• GPG Good Practice Guidance

• GWP Global Warming Potential

• IEA International Energy Agency

3Training Materials for National Greenhouse Gas Inventories


1A.4

Outline of this Presentation – Fuel Combustion

• Fuel combustion

• References (slide 7)

• Basic steps for estimation of emissions (slide 23)

• Relationships with other sources and sectors (slide 41)

• Quality control and completeness (slide 43)



1A.5

• Fugitive emissions

• Introduction

• Coal mining and handling

• Oil and natural gas systems

• Data issues

• References

Outline – Fuel Combustion



1A.6

Survey

Audience poll…

• Who has prepared a national inventory for your country?

• Who has worked on the energy sector?

Please share…

• Problems you have faced in preparing estimates for the energy sector

• Your plans for the future to improve your inventory.



1A.7

Reference Materials

• UNFCCC (COP decisions, reporting guidelines, etc.)

• 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)



1A.8

IPCC Guidance

• Fundamental methods laid out in the Revised 1996 IPCC Guidelines

• IPCC good practice guidance clarifies some issues (e.g. international bunker fuels)

and provides some updated factors…

• …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.



1A.9

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



1A.10

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.



1A.11

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





Example of Decision Tree

1A.13

Fuel Combustion - Autoproducers



Source: Revised 1996 IPCC Guidelines for national GHG inventories, Reference Manual – Volume 3, p. 1.32.

1A.14

Fuel Combustion - Mobile Sources

• Civil aviation

• Road transportation

• Cars

• Light duty trucks

• Heavy duty trucks and buses

• Motorcycles

• Railways

• Navigation

• International bunker fuels are reported separately.



1A.15

Carbon Dioxide (CO2) Emissions

• The calculation methodology is mass-balance-based.

• Oxidation of the carbon in fuels occurs 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.



1A.16

Carbon Flow for a Typical Combustion Process

• Most carbon is emitted as CO2 immediately.

• A small fraction emitted as non-CO2 gases:

• CH4, CO, non-methane volatile organic compounds (NMVOCs)

• Ultimately oxidizes to CO2 in the atmosphere

• Integrated into overall calculation of CO2 emissions

• Each carbon atom has two atmospheric lifetimes

• The remaining part of the fuel carbon is unburnt:

• Assumed to remain as solid (ash and soot)

• Account by using oxidation factors.



1A.17

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)

• Sulphur dioxide (SO2).



1A.18

Non-CO2 Emissions Require Detailed Process Information

• Combustion conditions

• Size and vintage of the combustion technology

• Maintenance

• Operational practices

• Emission controls

• Fuel characteristics.



1A.19

Methane (CH4)

• Emissions are a function of:

• methane content of the fuel

• hydrocarbons passing unburned through engine

• engine type

• post-combustion controls.

• Depends on temperature in boiler/kiln/stove.

• Highest emissions are in residential applications (e.g. small stoves, open biomass

burning, charcoal production).



1A.20

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



1A.21

Methods for Estimating 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 are required.



1A.22

Emissions by Source Categories - Fundamental Equation




1A.23

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.



1A.24

Step 1. Collect 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.



1A.25

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.



1A.26

Step 2. Common Energy Unit

• Convert :

o Fuel data into a common energy unit

o Production and consumption of solid and liquid fuels in tonnes

o 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.



1A.27

Step 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 tonnes 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: 20 tonnes C/TJ.

Coal• Depend on coal's rank and composition of hydrogen, sulphur, ash, oxygen

and nitrogen• Typical ranges: from 25 to 28 tonnes C/TJ.



1A.28

Step 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 industry.

• Attempt to use country-specific data instead of IPCC default carbon storage factors.




1A.29

Step 5. Multiply by an 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.



1A.30

Step 5. (Cont.) - Oxidation Factor Values

Natural gas

• Less than 1% 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 per cent left unburned

• IPCC default oxidation factor = 99%

• Recent research has shown 100% in autos.



1A.31

Coal

• Range from 0.6% to 6.6% 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), the range is from 1% to 10%

• No IPCC default.

31

Step 5. (Cont.) - Oxidation Factor Values



1A.32

Step 6. Convert to Full Molecular Weight and Sum

• Convert carbon to full molecular weight of CO2 and sum across all fuels.

• To express the results as CO2, multiply the quantity of carbon oxidized by the

molecular weight ratio of CO2 to C (44:12).



1A.33

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.



1A.34

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…

• Household fuelwood

• 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!



1A.35

Methods for Non-CO2 Emissions

Tier 1• 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.



1A.36

Fundamental Equation

Emissions = Σ(Emission Factorabc • Fuel Consumptionabc)

Where,

a = fuel type

b = sector activity

c = technology type including emissions controls.



1A.37

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.



1A.38

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.



1A.39

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. vehicle-

km-travelled/vehicle)

• Consider national emission standards, leaded gasoline prevalence, and

compliance with standards.

39

Mobile Combustion (cont.)





Example of Decision Tree

1A.41

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.



1A.42

Relationships with Other Sources and Sectors (cont.)

Waste sector:

• Combustion of wastes for energy purposes included in energy sector

• Incineration of plastics.

LULUCF sector:

• Biomass carbon implicitly accounted for.

Autoproduction of electricity

Fuel use for military purposes

Mobile sources in agriculture



1A.43

Quality Control and Completeness Checks

• All gases (CO2, CH4 and N2O)

• All source and subsource 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.



1A.44

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 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.



45

Thank you



CGE Training Materials National Greenhouse Gas Inventories Energy Sector – Fuel Combustion

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Transcript of CGE Training Materials National Greenhouse Gas Inventories Energy Sector – Fuel Combustion