8.1 Incineration
Categories 314 and 1579
8.1.1 Introduction
Categories 314 and 1579 estimate criteria pollutant emissions (particulate, organic, NOx, SOx, and CO) from waste material combustion at dwellings (e.g., in fireplaces and apartment house incinerators), commercial firms (e.g., in crematories and pathological incinerators), and industrial plants (e.g., in incinerators for waste disposal, reduction or preparation for recycling operations). Category 314 accounts for emissions from point sources in the Air District and emissions for category 1579 were obtained from area sources.
These categories do not include emissions from the combustion of any “auxiliary fuel” (e.g., natural gas or fuel oil) used to maintain the elevated temperatures needed to promote combustion of the waste material being incinerated. These categories also do not include emissions from solid fuel combustion for heating, cooking, or recreational purposes.
8.1.2 Methodology
Point Sources
Point Sources are operations that emit air pollution into the atmosphere at a fixed location within a facility, for which the Air District has issued a permit to operate, e.g. refinery cooling towers. These could also be a collection of similar equipment / sources located across multiple facilities, e.g. reciprocating engines.
During the permit to operate (PTO) issuance process, the BAAQMD collects information from the operating facility and/or determines from published literature, e.g. EPA’s AP-42, characteristics of a source including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. These characteristics are then stored for future use in the BAAQMD’s internal database. Facilities that hold a permit to operate are required to renew this permit periodically (this period varies based on facility and source type). Upon renewal, the facilities are requested to provide any updates to source characteristics as well as the source throughput for the last 12 months. This throughput, in combination with the emission factors and controls factors stored in the internal database, are used to estimate annual emissions at the source level. These source level emissions are then sorted and aggregated into categories.
Further speciation and quality assurance of emissions are performed as a part of the inventory process. The BAAQMD staff also perform a systematic crosswalk between CEPAM’s source category classification (Emission Inventory Code - EICs) and the District’s source category classification (category identification number - cat_ids), which ensures consistency in the annual emissions reporting process (CEIDARS) to California Air Resources Board. The last part of the inventory development process includes forecasting and back casting, and aggregation into sub-sectors and sectors for documentation purposes. For those years where no data is available, emissions data are backcasted to year-1990, as well as forecasted to year-2040 using either interpolation or another mathematical approach (see Trends section). Finally, emissions trends spanning from year 1990-2040 for each category and pollutant are evaluated for anomalies that are then investigated and addressed.
Category 314 is a point source category and follows the above methodology for emissions estimates. County distribution is determined by location of permitted sources in the Air District.
The PM2.5/PM and the PM10/PM ratios applied to these categories are consistent with size fractions of speciation profiles developed by the California Air Resources Board (CARB) and published on their emissions inventory web-page330.
For category 314, CARB PM speciation profile number is 134; PM2.5 constitutes 92.9% and PM10 constitutes 100% of total PM.
The ROG / TOG ratios applied to this category, or this group of related categories are based on an Air District internal speciation profile. Multiple data sources have been used for developing speciation profiles, such as Air District-approved source tests, TOG speciation ratios used by other regional air quality agencies, and relevant literature including latest speciation profiles developed by CARB 331 and the US Environmental Protection Agency (EPA)332.
For categories 314 ROG to TOG emissions ratio is 0.70. Further assessment and improvement of ROG / TOG speciation profiles has been planned in future inventory updates.
Area Sources
Category 1579 is considered an area source category since it covers 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
Area source emissions for category 1579 were estimated based on household waste generated in the San Francisco Bay Area. Most of the household waste in the Bay Area is collected and disposed of at the waste landfills. It is assumed that about a third of a percent (1/3%) of the total waste generated in the Bay Area is burnt through illegal fires.
More details on throughput, county distribution, emission factors and controls is provided in the following subsections.
(a) Activity Data / Throughput
Throughput for category 1579 is the estimated amount of waste materials burnt through illegal fires in the Bay Area. The total waste generation amount (tons/year) is estimated by multiplying the Bay Area population by an average amount of waste generated per resident. An average residential daily waste production of 1.6 pounds/person/day is assumed for the Bay Area. As noted above, it is assumed that about a third of a percent (1/3%) of the total waste generated in the Bay Area is burnt through illegal fires. The residential daily waste production data was obtained from the California Integrated Waste Management Board333 for year 1998.
(b) County Distribution / Fractions
For area source category 1579 county distribution is based on population data.
(c) Emission Factors
The emission factors for category 1579 were developed based on type of materials commonly found in household generated waste. The U.S. Environmental Protection Agency’s (EPA’s) document AP-42, Chapter 2.1, Table 2.1-4, Refuse Combustion334 contains information on combustion of waste materials. Emission factors for category 314 (a point source) are specific to source and facility and are provided either by the operator or estimated using published factors in literature.
(d) Control Factors
No District regulated emission controls apply to these categories.
(e) Speciation
Some pollutants included in this inventory can be further subdivided into sub-components. Particulate matter (PM) can be represented as fractions of Total Suspended Particulates (TSP), PM10, PM2.5, Black Carbon (BC) and Organic Carbon (OC). For category 1579, PM2.5 to PM emissions ratio is 0.927 and PM10 to PM ratio is 0.997.
Volatile Organic Compounds (VOCs) can be represented as Total Organic Gases (TOG), Reactive Organic Gases (ROG), and CH4 or Non-Reactive VOC component. Category 1579 ROG to TOG emissions ratio is 0.32.
8.1.3 Changes in Methodology
No changes to methodology were made in this version of the base year emissions inventory.
8.1.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
8.1.5 Trends
(a) Historical Emissions / History
Historical emissions for point source emissions are derived from source-specific throughputs provided by the permitted facility, compiled/reported emission factors, and regulation-based control factors. This information is archived in the BAAQMD’s internal database which is queried to retrieve the data for historical and current years. Interpolation techniques to account for missing data are used when necessary, this is the case for years 1991-1992.
Category 1579 accounts for emission from illegal burning of materials (trash) at residential dwellings. Trash collection for all residences, incorporated and unincorporated areas, was mandated in 1990. It was assumed that it will take a few years (1990-1995) to reach the goal of close to 100% trash collection for the entire Bay Area. It was expected that residential trash burning in all areas will go down drastically during first few years (1990-1995), but a very small amount (about 1/3 %) of illegal burning activity will continue at about population growth in the area.
(b) Future Projections / Growth
Forecasting of point source emissions is done based on calculations as shown in the equation below using recently updated growth profiles and a base year of 2020. The growth profiles for the current base year inventory have been verified and updated to represent the most likely surrogate for growing emissions for a given category up to year 2040. Forecasting for point source emissions includes impact of in-place regulations, but does not include estimation of controls that will theoretically be implemented as part of future policy emission targets or proposed regulation and legislation.
\[ \text{PE} = \text{Gr} * \text{Ci} * \text{Ei} \]
\(PE\) = projected emissions of pollutant i in a future year
\(Gr\) = growth rate by economic profile of industry or population
\(Ci\) = control factor of pollutant i based on adopted rules and regulations
\(Ei\) = base year emissions of pollutant i
It was assumed that annual emissions for waste burning would follow the population growth in the San Francisco Bay Area.
Population data were obtained from the Association of Bay Area Government’s (ABAG) 2017 “Projections” report335.
8.1.6 Uncertainties
Uncertainties may result from assumptions made for estimating the amount of waste materials burnt, therefore may lead to inaccuracies in emission estimations.
8.1.7 Contact
Author: Sukarn Claire
Reviewer: Ariana Husain
Last Update: November 06, 2023
8.1.8 References & Footnotes
PMSIZE. CARB. 2022. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎
ORGPROF. CARB. 2022. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎
SPECIATE. USEPA. 2022. https://www.epa.gov/air-emissions-modeling/speciate↩︎
California Integrated Waste Management Board. https://www.waste.ccacoalition.org/organization/california-integrated-waste-management-board↩︎
USEPA. AP-42. Refuse Combustion. https://www.epa.gov/sites/default/files/2020-10/documents/c02s01.pdf↩︎
Association of Bay Area Governments (ABAG). https://abag.ca.gov/↩︎