10.9 Animal Waste, Other
Categories 2347, 2348, and 2349
10.9.1 Introduction
Categories 2347, 2348 and 2349 account for total organic compound (TOG) emissions from waste products of domestic animals (pets) and other native animals including dogs, cats, deer, and wild pigs. These emissions were previously estimated in prior inventory iterations under one category that included all non-livestock animals (Category 760), but have since been separated.
Emissions are classified under the following category numbers:
| Category # | Description |
|---|---|
| 2347 | Dogs - Animal Waste |
| 2348 | Cats - Animal Waste |
| 2349 | Deer and Wild Pig - Animal Waste |
10.9.2 Methodology
These categories 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.
(a) Activity Data / Throughput
The animal population data is based on a July 2015 report by Lawrence Berkeley National Laboratory (LBNL) based on inputs to the CALGAPS (California LBNL GHG Analysis of Policies Spreadsheet) model462. There are more than a million dogs and 760,000 cats in the San Francisco Bay Area (SFBA) in year 2015.
(b) County Distribution / Fractions
Population of dogs and cats are estimated based on the ratio of household population of each county in the SFBA463, with Alameda (21.7%) and Santa Clara (25.5%) counties hosting the largest populations of domesticated pets. Category 2349 (deer and wild pig) is apportioned as per forest cover in each county.
(c) Emission Factors
All ‘other’ animal classes are assumed to have a CH4 emission factor of 0.5754 lbs/head. Emission factors for CH4 are assumed from the LBNL report1. The animal classes in this chapter are a source of TOG emissions as well. The TOG emission factors have been derived from an older California Air Resources Board Contractor Report on Uninventoried Emissions Sources in California464. A TOG emission factor of 12 lbs/head for dogs, deer and wild pigs, and 2.6 lbs/head for cats is assumed.
(d) Control Factors
Presently, no specific District regulations or controls have been instituted to reduce non-livestock animal emissions in the SFBA.
(e) Speciation
Since CH4 and TOG emissions are different for different classes of animals, the ROG / TOG ratios are different. They range from 78% ROG / TOG (for cats) to 95% ROG / TOG ratio (for dogs and deers).
10.9.3 Changes in Methodology
Emissions under these categories were previously estimated under a single category (760) in the past inventories (e.g. base year 2011 inventory). When the Air District developed its most recent GHG emissions inventory in 2017, the methodologies for these sources, category classification scheme and activity data sources were updated as speciated animal-class population data became available owing to work done by LBNL1.
The emission factors used in the new categories are also different from the single animal-class aggregated emission factor used previously (domesticated pets and wild animals were represented using one population estimate in previous inventory).
10.9.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
Based on the emission factors listed in the 1988 ARB report2, the TOG emissions from these categories range from 7000 tons/year (dogs) to 1000 tons/year (cats) to 70 tons/year (deer and wild pigs). These emissions are small when compared to the cattle livestock categories (see Chapter 10-08, 2333 through 2346) but quite large (Category 2347) when compared to many industrial sources.
10.9.5 Trends
TOG emissions from this set of categories depends on non-livestock populations in SFBA and evolution of emission factors over time. The two categories uses a range of base years to determine historical and future projected emissions. For historical emissions, 2011 is used as a base year for projections. For future emissions, 2015 is used as a base year for projections.
(a) Historical Emissions / History
For domesticated pets like cats and dogs, emissions through the years 1990-2010 were estimated based on Association of Bay Area Government’s annual household population trends2. Wild animal population data remains constant between 1990 and 2010, since there is very minor change in forest cover in the SFBA over time.
(b) Future Projections / Growth
Domesticated pet population activity data tracks with household population. Population forecasts are based on ABAG’s household population growth profile3 and this is used to project activity data (and subsequently emissions) from year 2016 through 2040. Deer and wild pig population is considered to track with forest cover in the SFBA which is expected to remain relatively unchanged in future years.
10.9.6 Uncertainties
The main source of uncertainties in this documentation are the representativeness of the emission factors for various animal classes. There is a fair amount of uncertainty in the accuracy of the TOG emission factors derived from the 1988 ARB report2, specially since the CH4 emission factors are much smaller than the TOG emission factors. The CH4 emission factor itself has evolved and decreased over successive BAAQMD inventory iterations.
The throughput for cats and dogs in the SFBA is based on human population-based indicators and surveys so there is a higher degree of predictability, but the activity data for deers is a big estimate and could have a high level of uncertainty. Thus the estimates for Category 2349 are the most uncertain among the three categories.
10.9.7 Contact
Author: Abhinav Guha
Reviewers: Tan M. Dinh and Yuan Du
Last Update: November 06, 2023
10.9.8 References & Footnotes
Greenblatt. 2015. Modeling California policy impacts on greenhouse gas emissions. Energy Policy, Volume 78, 2015, Pages 158-172, ISSN 0301-421. https://doi.org/10.1016/j.enpol.2014.12.024↩︎
ABAG. 2019. Plan Bay Area 2040. Association of Bay Area Government(ABAG). 2019. http://2040.planbayarea.org/reports↩︎
Dickson, R. and Tate, S. 1988. Evaluation of Emissions from Selected Uninventoried Sources in the State of California. Contract # A5-147-32, Radian Corporation, April 1988. https://ww2.arb.ca.gov/sites/default/files/classic/research/apr/past/a5-147-32.pdf↩︎