EMISSION INVENTORY SOURCE CATEGORY

METHOD SUMMARY

These categories include 1997 estimates of the emissions resulting from the combustion of natural gas in the residential sector. The combustion of natural gas in the residential sector is broken down into four categories: 1) space heating, 2) water heating, 3) cooking, and 4) unspecified. The unspecified category includes the combustion of natural gas in appliances such as clothes dryers, barbecues, and water heaters used for pools, spas and hot tubs.

ACTIVITY DATA SOURCE: The amount of natural gas consumed in the residential sector for each county in 1997 was obtained from the California Energy Commission report, "Quarterly Fuel and Energy Report, 1997 Residential Natural Gas Consumption." The amount of natural gas was apportioned into the four categories described above based on percentages from the California Energy Commission report, "Breakdown of California Natural Gas Usage by Appliance and by Utility Company for All Housing Types Combined." The actual percentage of natural gas used in each of the four categories varies according to which electric utility service area a county is located in. For counties in more than one air basin, the natural gas consumption was split based on population

EMISSION FACTOR SOURCE: The emission factors for residential natural gas combustion were obtained from EPA's AP-42.

TEMPORAL DATA:
Daily Activity: For space heaters, water heaters, and unspecified, the maximum activity occurs in the early daylight hours and in the evening hours, with average activity during the day and low activity at night.

For cooking, the activity occurs during meal time hours.

Weekly Activity: The activity is uniform seven days a week.

Monthly Activity: For space heaters, the monthly activity was based on monthly residential gas sales from the California Energy Commission. Activity occurs from November to June, with the highest months being December through April.

For water heaters, cooking, and unspecified, the monthly activity is assumed to be uniform throughout the year.

CHANGES IN METHOD AND EMISSION ESTIMATES: The emission factor for PM has been changed from 11.8 lb/mmcuft to 7.6 lb/mmcuft. The change was made because of updates to AP-42 made in March 1998. There were adjustments made to accurately represent utility coverage for each county. Riverside County was split to represent the new air basin and district designations.

DATE OF THE LAST UPDATE: November 1998

GROWTH PARAMETER: For space heaters, the growth parameters were developed by Pechan (Category 10 in their report, "Development of Emission Growth Surrogates and Activity Projections Used in Forecasting Point and Area Source Emissions, Final Report," February 26, 2001). The growth factors are based on population. For water heaters, the growth parameters were developed by Pechan (Category 11 in their report) and are based on real disposable income data. For cooking and unspecified, data on housing units were adjusted by Pechan using the Department of Energy's Annual Energy Outlook residential natural gas consumption projections.

STATEWIDE EMISSIONS SUMMARY (1997 - ANNUAL AVERAGE TONS/DAY)

CES No.	TOG	CO	NOX	SOX	PM
54569	3.08	11.18	26.28	0.17	2.12
54577	2.49	9.04	21.24	0.14	1.72
54585	0.40	1.46	3.44	0.02	0.28
47191	0.74	2.69	6.32	0.04	0.51
Total	6.70	24.37	57.28	0.37	4.63

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This page last revised on November 18, 2003

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