6.20 Dry Cleaning
Categories 105, 106, 107, and 1913
6.20.1 Introduction
Categories 105, 106, 107, and 1913 account for organic gas (TOG and ROG) emissions from the use of perchloroethylene, other synthetic solvents, and non-halogenated petroleum solvents during the dry cleaning process, respectively.
In the dry cleaning process, washing is conducted by agitating the fabric in a solvent bath. The next step is extraction where excess solvent is removed by centrifugal force. In the final step, drying is conducted by tumbling the fabric in a stream of warm air to vaporize and remove the solvent from the fabric. When the washing and extraction steps are performed in one machine and drying in a second machine, it is referred to as a transfer operation. When one machine performs all three steps, it is referred to as a dry-to-dry operation. Coin-operated dry cleaning machines, which are directly available for use by the consumer, typically involve dry-to-dry operations. These dry cleaning facilities emit organic emissions resulting from the use of solvent in cleaning process. The organic emissions may either be reactive (i.e. Stoddard solvent) or non-reactive (i.e. perchloroethylene). The amount of emission depends on the equipment type, amount of cleaning performed and operating practices. Dry cleaning equipment includes washers, dryers, solvent stills, muck cookers, still residues, and filter muck storage areas. Emissions may also come from leaks from pipes, flanges and pumps.
One of the most common dry cleaning synthetic solvents in use today is perchloroethylene, or PERC, a non-reactive organic material. However, PERC is a toxic and regulation has been put in place to phase out its use by the year 2023 239 . Category 105 represents PERC usage for point and area sources. There are currently no other halogenated solvents (Category 106) used in the District.
Other types of cleaning solvents used are non-halogenated petroleum solvents (Category 107 and 1913). These include both reactive solvents (i.e. Stoddard Solvent, DF- 2000, etc.) and non-reactive solvents (i.e. siloxane). Categories 107 and 1913 represent non-halogenated petroleum solvents usage for point and area sources, respectively.
6.20.2 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 and/or determines characteristics of a source from the operating facility including maximum throughput, emission factors for emitted pollutants, and control factors associated with downstream abatement devices. Depending on the evaluation of the BAAQMD, emission factors as provided by the facility or those available through publications e.g. from the EPA, are finalized and stored in an internal database. Facilities that hold a permit to operate with the BAAQMD 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 the source characteristics currently stored 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 second half of the inventory development process includes forecasting and back casting and aggregation into sub-sectors and sectors for documentation purposes.
Categories 105, 106, and 107 are considered point source categories and follow the above methodology for emissions estimates.
Area Sources
Categories 1913 is considered an area source category as it covers sources that are not explicitly permitted or individually cataloged by the District. 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
All PERC and other halogenated solvent use is permitted by the District, however not all use of non-halogenated solvents is permitted. Emission from sources that use non-halogenated solvents that are not permitted by the District are covered under category 1913.
Unlike other area source categories, the methodology for 1913 is the same as for point source categories with the exception that it applies to registered sources. Similar to permitted sources, these sources registered their device with the District but are not required to update throughput on an annual basis. Therefore, for registered equipment, the maximum operational data that is collected upon registration is what is used to estimate emissions from these sources.
The speciation applied to TOG, for all noted categories, to determine ROG is consistent with the size fractions of speciation profiles developed by the California Air Resources Board (CARB) and published on their emissions inventory web-page 240.The total organic gas (TOG) emitted from these three categories is considered to be all reactive (i.e. TOG equals ROG).
6.20.3 Changes in Methodology
Previous to this base year, category 1912 represented sources using PERC that may have not been permitted by the District and therefore were not included in point source category 105. Further data repair has been performed on Category 105 to include emissions that were previously covered under category 1912. Therefore, category 1912 has been retired and is no longer represented separately in this inventory.
6.20.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.20.5 Trends
The District originally adopted District [Rule 8-27], for Synthetic Solvent Dry Cleaning Operations as an ozone control measure in May 1980. This rule was amended in March 1982, November 1984, and September 1990 with additional operating requirements. In 1994, the District adopted [Rule 11-16] to incorporate new regulatory standards adopted at the state and federal levels. [Rule 11-16], with its new solvent standards and control requirements, replaced [Rule 8-27]. [Rule 8-27] was retained as part of the District’s regulations for State Implementation Plan (SIP) considerations, however, in March 2009 was deleted.
District [Rule 11-16] (Perchloroethylene and Synthetic Solvent Dry Cleaning Operations), passed in December 1994 required more stringent requirements on controls, monitoring, ventilation, secondary controls, and certain prohibition of usage of certain machines. In March 2009, [Rule 11-16] was amended to incorporate into the District rule a state law phase out schedule that would eliminate the use of Perchloroethylene in dry cleaning by January 1, 2023.
District [Rule 8-17], adopted in May 1980, set operating and emission control requirements to dry cleaning operations using petroleum solvents. In March 1985 and September 1990, this rule was amended to reflect additional control and operating requirements. Some of the newer alternative technologies currently available include some non-halogenated photochemical organic compounds (POC) and non-photochemical organic compounds (NPOC). To reflect the expanded applicability of this rule and update the equipment standards and control requirements, [Rule 8-17] was amended again in March 2009. The title of this rule was also changed from “Petroleum Solvent Dry Cleaning Operations” to “Non-halogenated Dry Cleaning Operations”.
(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.
Over the past years, PERC usage has decreased significantly. As a result of regulatory requirements and its toxicity, dry cleaners have been switching to other cleaners, such as non-halogenated hydrocarbon solvents. In March 2009, amendments were made to District [Rule 11-16] in order to phase out all PERC usage in dry cleaning operations by 2023.
(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
The phase out of PERC is predicted to increase usage of the non-halogenated petroleum solvents (Categories 107 and 1913). After 2012, the growth profiles for these two categories were based on data from a 2008 BAAQMD workshop report241 on dry cleaner emissions projections (Figure III-A1) and the Association of Bay Area Government’s 2017 population growth profile242.
6.20.6 Uncertainties
For categories 107 and 1913, there is uncertainty in the throughputs that are used as the basis for emissions estimates for historical and present years. This uncertainty lies in the default throughput that is used for registered equipment. This default may be over estimating actual emissions attributed to this category as it represents the maximum emissions allowed per dry cleaner.
6.20.7 Contact
Author: Ariana Husain
Reviewer: Michael Nguyen
Last Update: November 06, 2023
6.20.8 References & Footnotes
BAAQMD. 2009. Regulation 11 Rule 16: Perchloroethylene and Synthetic Solvent Dry Cleaning Operations, https://www.baaqmd.gov/rules-and-compliance/rules/reg-11-rule-16-perchloroethylene-and-synthetic-solvent-dry-cleaning-operations↩︎
CARB. 2022. ORGPROF; https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎
BAAQMD. 2008. Workshop Report. https://www.baaqmd.gov/~/media/files/planning-and-research/rules-and-regs/1116_wsrpt_120908.pdf↩︎
ABAG. Association of Bay Area Governments : Open Data Catalog. [accessed 2023 Jan 30]; https://abag.ca.gov/tools-resources/data-tools/open-data-catalog↩︎