6.22 Adhesive Sealants
Categories 117, 118, and 1901
6.22.1 Introduction
Categories 117, 118, and 1901 account for fugitive organic emissions from the usage of solvent and water base adhesive sealants.
Adhesives and sealants are primarily used in wood, wood-related, and packaging activities. The emissions reported in these categories include emissions resulting from both industrial and consumer usage of adhesives and sealants. Emissions are comprised of volatile organic compound (VOC) emissions. Emissions in categories 117 and 118 include emissions from District’s permitted (point) sources using solvent-base and water-base adhesives respectively. Category 1901 emissions are from non-permitted (area) sources which do not meet the threshold level to require a permit to operate from the District. These non-permitted sources are from adhesive and sealant industries which are much smaller in scale of operation comparing to the permitted sources.
Adhesives and sealants are generally categorized and distinguished by source types. Most adhesives and sealants are either of a water-based type or of a solvent-based type.
Raw materials primarily used in the production of adhesive and sealants are rubber, starch, animal glues, bitumen, and synthetic resins. Other materials of smaller quantity that can be found in adhesive and sealant formulations include phenolic resins, formaldehyde, polyolefins, polyvinyl acetate, acrylics, polyvinyl chloride, polyesters, polyvinyl alcohol, and solvents, including hexane, heptane, xylene, toluene, methylene chloride, and 1,1,1-trichloroethane.
6.22.2 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.
Categories 117 and 118 are considered point source categories and follow the above methods for emissions estimates. To limit and reduce organic compound emissions from these categories, District’s Regulation 8, Rule 51, Adhesive and Sealant Products Rule 249 regulates organic compound emissions from various adhesive and sealant manufacturers in the Bay Area. The regulation was adopted in November 1992.
Area Sources
Category 1901 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
More details on throughput, county distribution, emission factors and controls is provided in the following subsections. Emissions from adhesive and sealant used in non-permitted industries are usually estimated at the unit of a geographical area, e.g., county. Non-permitted industries includes construction sites, small industrial companies, transportation facilities, dental and medical buildings, electric and electronics facilities, and other miscellaneous sites. Some of the industries not affected under the District’s permit system and unregulated for the usage of adhesives and sealants include small wood production manufacturers and small wood related construction companies as well as small packaging companies.
(a) Activity Data / Throughput
Point Sources
Throughputs of point sources are collected as referenced in the Methodology section of this chapter.
Area Sources
Throughput data used to estimate area sources emissions are based on “The Rauch Guide to the U.S. Adhesives and Sealants Industry, 2000-02 Edition”250. Adjustments were made for year 2015 using the growth in construction industry for each county which are derived from projections generated by the Association of Bay Area Governments251. For the adjustment, the growth rate derived from this ABAG projection was applied to the throughput to generate the throughput for base year 2015.
(b) County Distribution / Fractions
For point sources, the physical location of each facility using adhesives as reported in the District’s permitting system was used to distribute emissions for each county.
For area sources, the county distribution is based on adhesive and sealant manufacturers data collected by the US Census data 252. The data gathered includes data collected from various adhesive and sealant manufacturers at the nine different counties of the District. The data includes the number of adhesive and sealant establishments in the county, the employee size, and annual payroll. This data was used to distribute emissions for each county.
(c) Emission Factors
Point Sources
Emission factors for point sources are collected and used as referenced in the Methodology section of this chapter.
Area Sources
Emission factors used in the calculation of these area sources, which were taken from ARB’s report titled “Adhesives and Sealants” 253, are 1,230 lbs. of VOC per ton of solvent-borne adhesives/sealants and 90 lbs. of VOC per ton of water-borne adhesives/sealants.
(d) Control Factors
District Regulation 8, Rule 511 set limitation standards on adhesive products effective from January 1995. This Rule has helped to lower VOC emissions from the usage of adhesives and sealants.
(e) Speciation
The ROG/TOG ratios applied to 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 CARB254 and the US Environmental Protection Agency255. For this group of categories, ROG constitutes 100% of TOG. Further assessment and improvement of ROG/ TOG speciation profiles has been planned in future inventory updates.
6.22.3 Changes in Methodology
There are no changes in the methodology to estimate emissions in the current base year inventory compared to the previous base year inventory (year 2011).
6.22.4 Emissions
A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.
6.22.5 Trends
Albeit future rules and controls on both point and area sources which are unknown at this point, the growth in emissions of the adhesive and sealant industry is expected to correlate with the growth of its activity level. The jobs manufacturing wholesale growth forecasts put forward by ABAG3 seem to best represent the growth of activity within the categories under adhesive and sealant and so this manufacturing growth profile is used to forecast emissions into future.
(a) Historical Emissions / History
Historical emissions for point source emissions (categories 117 and 118) 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.
Historical emissions from area source emissions (category 1901) are estimated using emissions from District’s point source adhesive and sealant manufacturing facilities (Category 117) and adjusted proportionally from overall adhesive and sealant manufacturers data collected by the US Census data4. As previously mentioned, historical emission has significantly decreased since the adoption of District Regulation 8, Rule 51 1, which limits volatile organic compound emissions from adhesive and sealant operations.
(b) Future Projections / Growth
For a given category or a group of related categories, future emissions estimates were developed using a growth profile based on data available from a handful of resources. These resources include employment- and population-based growth projections generated by the Association of Bay Area Governments3, fixed-percentage growth assumptions consistent with historical emissions data trends, and specific growth profiles derived using relevant regional or sub-national data sources (e.g. county-specific wine production data from the Wine Institute for wine fermentation categories, California crude oil distillation capacity data from the Energy Information Administration for refinery categories, and California Energy Commission natural gas usage projection data for residential and commercial natural gas combustion categories). For these categories, the growth profile is based on the above ABAG’s3 construction industry projection in the Bay Area.
\[ \text{PE} = \text{Gr} * \text{Ci} * \text{Ei} \]
\(PE\) = 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
6.22.6 Uncertainties
Throughputs for the point source categories are reported by all adhesive and sealant manufacturing facilities via the BAAQMD permit system requirement on a year by year basis and are assumed to reflect the most current data available at the time. Throughput data that are taken based on source test is considered the most accurate, followed by engineering calculations such as mass/material balance.
For both point and 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.
6.22.7 Contact
Author: Tan Dinh
Reviewer: Abhinav Guha, Yuan Du
Last Update: November 06, 2023
6.22.8 References & Footnotes
BAAQMD. 2002. Reg 8-51. https://www.baaqmd.gov/rules-and-compliance/rules/reg-8-rule-51-adhesive-and-sealant-products↩︎
Grey House Publishing Incorporated. Rauch Guide to the US Adhesives Industry 2002. https://www.haugenbok.no/rauch-guide-us-adhesives-industry/9781592371297↩︎
Plan Bay Area 2040. ABAG 2017. http://2040.planbayarea.org/files/2020-02/Final_Plan_Bay_Area_2040.pdf↩︎
U.S. Census Bureau. Data ; [accessed 2023 March 13]. https://data.census.gov/table↩︎
CARB. Section 3.7 : Adhesives and Sealants. [accessed 2023 March 13]. https://www.arb.ca.gov/ei/areasrc/fullpdf/full3-7.pdf↩︎
ORGPROF. CARB 2022. https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎
SPECIATE. USEPA 2022. https://www.epa.gov/air-emissions-modeling/speciate↩︎