# Presentation: 061617

## Estimating Emissions of Greenhouse Gases:  Carbon Dioxide	

- Presentation to the
- Department of Energy,
- Republic of the Philippines
- September 17, 1997
- Arthur Rypinski
- Energy Information Administration
- U.S. Department of Energy
- Courtesy of the US Agency for International Development

## Presentation Plan

- Basic Principles
- How Much Accuracy Do You Need?
- Designing and Estimation “Strategy”
- Collecting the Data
- Making the Estimate

## Basic Principles

- Fossil fuels are predominately “hydrocarbons,” compounds containing carbon and hydrogen atoms bonded together.
- The process of combustion breaks the hydrocarbon molecule into its constituent parts, and releases energy, and rebonds the carbon molecules with oxygen to form carbon dioxide, and the hydrogen molecules with oxygen to form water vapor.
- For methane:  CH4 + 2O2 ---> CO2 + 2H2O

## Basic Principles--continued

- Combustion of fossil fuels in modern engines is nearly complete.
- The carbon content of fuels is relatively stable over time, and relatively well understood
- Therefore, “mass balance” emissions estimation works well.
- TO ESTIMATE EMISSIONS, TAKE ENERGY CONSUMPTION BY FUEL, MULTIPLY BY THE CARBON CONTENT OF THE FUEL

## Calculation of Philippine Emissions:  First Approximation

## Units Alert

- Carbon emissions are typically reported in metric units either as carbon dioxide, or as carbon (to get to carbon dioxide from carbon multiply by 44/12 =3.66666
- This lecture assumes all energy units are in higher (gross) heating value.  HHV is about 5 percent higher than LHV for petroleum, and coal, about 10 percent higher for gas.

## How Much Accuracy Do You Need?

- There are many ways to refine and improve this estimate.  Some of these improved methods are very data and computation intensive.  However, the refinements may not produce a large change in the estimate.
- The analyst must decide how much precision is necessary for the analytical task at hand.

## Designing an Estimation Strategy:  Decision Criteria

- Quality (absolute and relative) of data;
- Accessibility of the data;
- level of precision required for the intended use of the estimate;
- the amount of effort available to improve the estimate.

## Consumption-Based (Bottom-up) vs. Net Supply (Top-Down) Approach

- “Bottom-Up” approach calculates emissions based on reported end-use “consumption” of individual petroleum products (gasoline, etc.) and fuels consumed by electric power plants
- “Top-Down” approach calculates emissions based on production + imports - exports + stock change of fossil fuels (crude oil, coal, natural gas)

## Top-Down Approach

- Pros:
- In many countries, production and trade data is more complete and reliable than consumption data, so may be more accurate.
- Usually quick and easy to do.
- Cons
- Not very useful for mitigation policy analysis
- May exclude important emissions sources
- crude oil carbon content is important, but hard-to-measure, input.

## Bottom-up Approach

- Pros-
- Much more useful for policy analysis
- Cons
- Much more data and computation intensive;
- Requires a more thorough understanding of national energy systems;
- Data deficiencies may cause underestimate of emissions
- If you use a bottom-up approach, always do a top-down analysis, too.

## Estimation Strategies:  Other Issues

- What areas do you wish to include?
- Biofuels
- Geothermal
- Non-fuel use
- Industrial process emissions
- flare gas and energy industry own use
- bunker fuels
- Standard vs. national emission factors

## Estimation Strategy Issues--continued

- Land use emissions from deforestation and forest regrowth are probably very important in the Philippines
- Which gases to cover?
- carbon dioxide only
- add methane, nitrous oxide, HFCs, PFCs, SF6
- add CO, NMVOCs, nitrogen oxides.

## Collecting the Data

- Energy Supply/Consumption
- Fuel Characteristics/Emissions Factors
- Industrial Processes
- Non-Fuel Use

## Collecting Energy Data

- WATCH THE UNITS!  Understand the units in which the data was originally collected; and any subsequent conversions.
- Be sensitive to possible data problems:  unreported or mis-reported consumption or trade; unreported military use
- Try to cover refinery fuel, flare gas, and energy producer own-use.

## Fuel Characteristics and Emissions Factors: Petroleum

- crude oil is a mixture of hundreds or thousands of different hydrocarbon compounds, and includes certain impurities (especially sulfur)
- Refining sorts these compounds directly by boiling temperature and indirectly by density and size of molecule
- Light products will be composed almost entirely of hydrocarbons; the impurities will be concentrated in the residual oil.
- The hydrocarbon portion of petroleum products is typically 84-86% carbon by weight; but density varies much more.

## Petroleum--continued

- To calculate an emissions factor for a petroleum product:
- Determine density;
- subtract known impurities (e.g. sulfur)
- Use ultimate analysis to determine carbon content; OR
- assume 85% carbon content for the hydrocarbon portion (except LPG)

## Petroleum Emissions Factors

- Source:  derived from EIA, *Emissions of Greenhouse Gases in the United States, 1995*.

- Green=non-fuel use.

## Emissions Factors:  Coal

- Coal varies enormously (50%) in heat content per ton, due to variations in moisture and ash content.  Internationally traded steam coal varies much less.
- Coal varies about 10 percent in carbon per unit heat content, due to variations in the hydrogen/carbon ratio.

## Emissions Factors:  Coal

- To calculate emissions factor for coal:
- Get an ultimate analysis for each source of coal; this will show carbon content per ton directly; OR
- Get heat content of coal for each source, and estimate carbon content from known characteristics (bituminous, high volatile, etc.)
- OR, assume 25-26 MT carbon/10^9 Btu (25.7 preferred for international steam coal)

## Emissions Factors:  Natural Gas

- Natural gas in the reservoir can have large variations in composition; with significant inerts (carbon dioxide or nitrogen) or significant liquids content.
- Processing for pipeline use will typically remove most of the liquids and may reduce impurities.  Pipeline quality gas is far more homogenous than raw natural gas.  Typical composition would be 92-97% methane, 2-5% ethane, propane, butane, 0-3% inerts.
- Regasified LNG is usually very close to pure methane.

## Natural Gas

- To calculate emissions factors for natural gas; obtain composition analysis; calculate carbon content of methane, ethane, propane, butane, pentanes plus; sum, divide by heat content; OR
- assume about 14.40 metric tons carbon per 10^9 Btu (your error will be very small)
- Don’t forget energy consumption from LNG regasification and gas production may not be included in energy consumption statistics.

## Industrial Processes

- Industrial process emissions are carbon dioxide emissions not caused by combustion of fossil fuels.  Typically, they come from using limestone (calcium carbonate, CaCO3) to make lime, usually for cement
- 	CaCO3 + heat ---> CaO (lime) + CO2
- Other uses of limestone that emit carbon dioxide include iron and steel, copper, and lead smelting; possibly fertilizer use.

## Industrial Processes-Continued

- There are also an array of sodium carbonate (soda ash) chemical processes that emit carbon dioxide, but these are typically very small.
- Industrial/commercial carbon dioxide is typically derived from fossil fuel use; especially ammonia fertilizer manufacture.

## Estimating Cement Emissions

- To calculate emissions from cement production:  lime content of cement is typically 63.5 percent.
- Molecular weight of lime is 40.07 (Ca) + 16.01 (O)=56.08; one mole of carbon (12) is released for each mole of lime; so
- Tons cement x .635 x (12/56.08) = emissions
- To compute emissions from limestone inputs; limestone is 98 percent CaCO3, molecular weight of CaCO3 is 40.07+(3x16.01)+12=100.09, so
- Tons limestone x .98 x 12/100.09 = emissions

## Limestone in Copper Smelting

- Limestone is often used in copper smelting in a ratio of 0.2 kg limestone/kg copper concentrate
- Emissions factor: 0.2 x (12/100.08) =  0.0239984 kgC/kgCu
- It would be highly desirable to confirm limestone usage/quantities with Philippine copper smelters before incorporating

## Philippine Industrial Process Emissions

## Non-Fuel Use

- Some fossil fuels are not combusted; rather they are used in ways in which the carbon content of the fuel does not end up in the atmosphere.
- Some examples of non-fuel use:  asphalt for road paving; petrochemical feedstocks used to make plastic; solvents; lubricants.
- Some non-fuel uses may partially or wholly end up in the atmosphere.

## Non-Fuel Use--continued

- In the Philippines most non-fuel use can probably be inferred from the petroleum products slate.  Non-fuel use of “ordinary” petroleum products will be very difficult to detect.
- Philippine reported naphtha data is odd and deserves further investigation

## Non-Fuel Use:  Fraction Sequestered

- The IPCC suggests the following coefficients for the fraction of various petroleum products not combusted:
- Lubricants:  50 percent
- Naphtha:      75 percent
- Asphalt       100 percent
- EIA assumes 0 percent for solvents.  (NMVOCs decay into carbon dioxide)

## Philippine Non-Fuel Use

## Making the Estimate

- Adopting a “Top Down” strategy, we can draw coal consumption and petroleum products consumption from PDOE sources; and emissions factors from standard sources.
- To estimate, multiply petroleum products consumption by Btu by emissions coefficient.
- Deduct non-fuel use, add geothermal, coal, and industrial process emissions.

## Slide 33

## Slide 34

## Estimation Issues

- Treatment of “Refinery Fuel/Losses” (defined as “still gas” here)
- Geothermal not included
- Biomass not included (IPCC recommends excluding biomass)
- Treatment of bunker fuels is uncertain (to me)
- “First Approximation” differs from the more detailed estimate; it would be interesting to study the reasons.

## Slide 36