Appendix C

Procedures for Estimating Biomass Consumption Levels

Procedure for Industrial Sector Woodfuel Consumption

Industrial wood consumption data for 1990 were derived using the 1988 Manufacturing Energy Consumption Survey (MECS) conducted by EIA. Estimates for 1990 were developed by multiplying the 1988 MECS wood energy consumption value by the ratio of total industrial energy consumption in 1990 to total industrial energy consumption in 1988.

For 1991, consumption estimates from the 1991 MECS survey were used.

For 1992 through 1994, estimates were based on the 1991 MECS survey, combined with an assumed growth rate of just under 2 percent annually. This reflects historical growth in the pulp and paper industry, the largest industrial consumer of wood energy.

MECS data used include selected wood inputs of energy for heat, power, and electricity generation consumed in the following fuel categories:

Waste materials
Pulping liquor
Roundwood
Wood chips, etc.

Regional and sectoral woodfuel consumption values from 1991 through 1994 were derived by applying the 1990 sectoral and regional distributions presented in Estimates of U.S. Biofuels Consumption 1990. This procedure was used because significant portions of the 1991 MECS wood consumption data by industrial sector and by region were withheld due to disclosure requirements and/or estimated standard errors that were greater than 50 percent.

Procedure for Residential Sector Woodfuel Consumption

Residential woodfuel consumption estimates for 1990 through 1994 could not be obtained from EIA surveys. The most recent data reported in EIA's Residential Energy Consumption Survey (RECS) were for 1990 (582 trillion Btu total). The procedure used for estimating residential fuelwood consumption these years consisted of applying the ratios of population-weighted regional heating degree days to each regional RECS value, respectively. Use of this procedure was based on the assumption that the residential sector consumed the same amount of wood per heating degree-day.

For 1990, survey estimates from the 1990 RECS were used. For 1991, consumption was estimated as follows:

C = C' (a/b)

where:

C = 1991 estimated consumption
C' = 1990 RECS consumption
= 582 trillion Btu
a = heating degree-days for 1991.
b = heating degree-days for 1990.

The same approach was used to estimate 1992 through 1994 residential woodfuel consumption.

Procedure for Electric Utility Sector Woodfuel Consumption

The 1990 through 1994 electric utility woodfuel consumption data were obtained by contacting each electric utility that reported woodfuel use on Form EIA-759, þMonthly Power Plant Report,þ to determine the number of short tons burned by each facility in each year. For plants that reported consumption in short tons of green wood (tons of wood containing 50 percent or more water by weight), consumption data were converted into oven-dried short tons using the following formula:

ODST = GT x CF

where:

ODST = oven-dried short ton.
GT      = green tons consumed
CF      = (8,000,000 Btu per green ton) /
              (17,200,000 Btu per oven-dried short ton)
           = 0.465 oven-dried short tons per green ton.

Procedure for MSW and Landfill Gas Estimates

Municipal solid waste (MSW) and landfill gas estimates for 1992 were derived from data contained in Governmental Advisory Associates (GAA), Resource Recovery Yearbook(1) and Methane Recovery Yearbook.(2) The following specific steps were taken to calculate both MSW and landfill gas consumption estimates for 1992.

Municipal Solid Waste

Steam Plants. For steam-only plants, the following equation was used:

Thermal output (trillion Btu) = [Steam output (pounds per hour) x Btu per pound of steam x days operating per year x 24 hours per day] /

Electricity Plants. For electricity-only plants, the following equation was used:

Thermal output (trillion Btu) = [MSW throughput (tons per day) x 2,000 pounds per ton x days operating per year x Btu per pound of MSW] /

Electricity and Steam Plants. For electricity-and-steam plants, the equation for electricity-only plants was used.

Landfill Gas (Methane)

The following equation was used to derive estimates of consumption for 1990:

Thermal output (trillion Btu) = [Cubic feet of methane produced per day x Btu per cubic foot of methane x (365 days - days shut down)] / 10^12^.

For plants producing pipeline-quality gas, the Btu per cubic foot value for treated gas was used. Data for 1992 are not yet available; however, GAA estimates that by the beginning of 1994, landfill gas energy consumption had increased by 25 percent from 1990 levels. The estimates for 1990 were increased by 25 percent to obtain 1992 consumption.

Procedure for Manufacturing Waste Estimates

The 1991 and 1992 manufacturing waste estimates were derived by applying the 1991/1990 and 1992/1990 total industrial energy consumption ratios to the estimated 1990 values, respectively.

Procedure for Fuel Ethanol Consumption Estimates

The 1992 through 1994 ethanol consumption estimates were derived from EIA's (Petroleum Supply Division) ethanol production data, change in stocks, and net imports as reported on Form EIA-819M. Specifically, consumption was derived as:

Consumption = Production - Stock Changes.(3)

Fuel ethanol consumption estimates for 1990 and 1991 were compiled from fuel alcohol production and import data collected by the Bureau of Alcohol Tobacco and Firearms (BATF) and fuel ethanol export data collected by the Foreign Trade Office, Bureau of the Census. BATF production data were collected from two statistical releases, "Alcohol Fuel Production" and "Distilled Spirits." The Bureau of the Census fuel ethanol export data were obtained from Schedule B, Commodity Number 2207.20.0000, "Ethyl Alcohol, Denatured of Any Strength (for Nonbeverage Use)."

Fuel ethanol consumption was derived from the two BATF statistical releases and Bureau of the Census export data as follows:

Fuel Alcohol Production + Imports for Fuel Use - Exports of Ethyl Alcohol.(4)

BATF alcohol fuel production and import data are reported in proof gallons and have been converted to wine gallons. (Two proof gallons are approximately equal to one wine gallon). Census export data were reported in wine gallons prior to 1989 and in liters thereafter. Export data reported in liters have been converted to wine gallons. (One liter is equal to 0.264 gallons). A heating value of 76,400 Btu per gallon was used to convert gallons to Btu.

Regional distributions for all years were based on gasohol sales data published by the U.S. Department of Transportation, Federal Highway Administration.(5)

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