7.2 Domestic Fuel Combustion - LPG & Liquid Fuel
Categories 286 and 287
7.2.1 Introduction
Categories 286 and 287 account for emissions from domestic fuel combustion of liquefied petroleum gas (LPG) and distillate oil, respectively
LPG is comprised of a flammable mixture of hydrocarbon gases that has undergone a liquification process and is stored in a pressurized container prior to usage. Depending on the bulk of the mixture components, the names often reference to by this fuel include propane, butane, and propylene. Distillate oil or distillate fuel oil is a petroleum product derived from the left over of distillation or refining of crude oil. It is usually made up of heavier components of the refine crude petroleum mix. Although there are many grades, distillate fuel oil product, such as No. 1, No. 2, and No 4 fuel oils, are generally used for space heating. The emissions reflected herein include all five criteria pollutants (PM, VOC, NOx, SOx, CO).
7.2.2 Methodology
Categories 286 and 287 are considered an area source category since they cover facilities / emission sources that are not directly permitted by the District, and hence not systematically cataloged. Emissions for area source categories are determined using the formula:
Current Year Emissions = Base Year Emission X Growth Profile, and,
Base Year Emission = Throughput X Control Factor X Emission Factor
where,
- throughput or activity data for applicable base year(s) is determined using a top-down approach (e.g. state-, national-level data);
- emission factor is derived from general literature, specific literature and reports, and/or source testing results provided by Air District staff;
- control factor (if applicable) is determined by District and state rules and regulations in effect;
- and, historical backcasting and forecasting of emissions is based on growth profiles as outlined in the Trends section of this chapter
More details on throughput, county distribution, emission factors and controls is provided in the following subsections. Emissions estimates from domestic LPG and distillate oil combustion are based on the “British thermal unit (BTU) equivalent - natural gas approach”.
(a) Activity Data / Throughput
The activity data (throughputs) are derived from the following data, namely:
- Number of housing units heated by LPG and distillate oil as provided by the 2010 Department of Finance’s Census of Population and Housing277.
- Bay Area natural gas fuel usage as provided by Pacific Gas and Electric Company.
- Natural gas usage conversion to average BTUs per household.
From the data above, an estimate of LPG and distillate oil usage based on average BTUs per house hold is calculated for the base year.
(b) County Distribution / Fractions
County distribution of emissions was based on the Department of Commerce’s 2010 Census of Population and Housing for California278. In that report, the number of homes using LPG and fuel oil as a heating medium in each county was used in the estimate of county distribution.
(c) Emission Factors
Emission factors are taken from (EPA, AP-42 oil and lp fuel data)279.
(d) Control Factors
There are no applicable control factors for these categories.
(e) Speciation
For LPG and distillate oil, CARB’s organic gas speciation profile #121 and #112 were applied respectively. The profiles closely match those used by CARB for the combustion of LPG and distillate oil fuels in their air quality modeling work.
7.2.3 Changes in Methodology
No changes to methodology were made in this version of the base year emissions inventory.
7.2.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
7.2.5 Trends
(a) Historical Emissions / History
Historical emissions for category 286 follow household population data while that of category 287 has been estimated to decrease over the past years at 2% annum. This reduction in category 287 is due to users switching of fuel in favor of natural gas.
(b) Future Projections / Growth
For Category 286 (Fuel Combustion, Stationary Sources, Domestic LPG), an assumption was made that annual emissions, over the years, would tend to follow household population data. Population data used in the projection was based on the Association of Bay Area Government’s (ABAG’s) 2017 “Projections” report280. For Category 287 (Fuel Combustion, Stationary Sources, Domestic Distillate Oil), the growth was assumed to be diminished as the fuel would eventually be phased out in favor of natural gas. A 2% reduction per year was chosen, starting in 1992.
7.2.6 Uncertainties
For area source emission factors, the main uncertainty in the updated methodology arises from the use of emission factors for certain categories that remain constant over several decades although technological controls may have been applied at facilities. Additionally, the emission factors themselves are seldom verified and validated against measurements, in part due to the difficulty in measuring fugitive emissions from area sources.
7.2.7 Contact
Author: Tan Dinh
Reviewer: Abhinav Guha, Yuan Du
Last Update: November 06, 2023
7.2.8 References & Footnotes
California Department of Finance. Census 2010. [accessed 2023 March 13]. https://dof.ca.gov/reports/demographic-reports/census-2010/↩︎
U.S. Department of Commerce. 2010 Census of Population and Housing. 2012. [accessed 2023 March 13]. https://www2.census.gov/library/publications/decennial/2010/cph-2/cph-2-6.pdf↩︎
USEPA. AP42. [accessed 2023 March 13]. https://www.epa.gov/air-emissions-factors-and-quantification/ap-42-compilation-air-emissions-factors↩︎
ABAG. Association of Bay Area Governments Open Data Catalog. [accessed 2023 Jan 30]; https://abag.ca.gov/tools-resources/data-tools/open-data-catalog↩︎