4.6 Metallurgical, Foundry & Forging Operations; Metal Recycling & Shredding Operations

Categories 34, 2221, 2222, 2223

4.6.1 Introduction

Categories 34, 2221, 2222, and 2223 cover sources of particulate matter (PM) emissions, some of which may be listed as toxic air contaminants, and total organic compounds (TOG), some of which may also be odorous compounds from foundries, forging operations, and metal recycling and shredding operations. Foundries and forges process ferrous (iron based) metals, non-ferrous metals (i.e. aluminum, copper, magnesium, zinc, brass, and bronze), or a combination of both. Metal recycling and shredding facilities collect, sort, and recycle scrap metal. Scrap metal includes both ferrous and non-ferrous metals and is often shredded.

Process equipment that emit the pollutants mentioned include furnaces (cupola, electric arc, reverberatory, etc.), temporary mold and core making, metal casting, cooling, shakeout, and sand reclamation, shredders, etc. Many of these pieces of equipment/process are permitted by the District and are considered point sources. Emissions from these processes are accounted for under categories 34 and 2222.

In addition to point sources, various other processes and emission sources at these facilities, such as tapping, pouring and casting, cooling, shakeout, metal management, sorting separation, open spaces, are the primary sources of fugitive emissions. The fugitive PM emissions from these processes and sources are considered area sources (Categories 2221 and 2223).

4.6.2 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 34 and 2222 contain PM and TOG emissions from point sources only.

Area Sources

Categories 2221 and 2223 are considered an area source categories 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

Fugitive PM emissions from Category 2221 were estimated using a BAAQMD engineering analysis of PM emission at four of the larger foundries and forges within the District. The fugitive PM emissions at three of these facilities were estimated to be between 60% - 85% of the total (fugitive and abated) PM emissions. The fugitive PM emissions at the fourth facility, though small, was estimated from its recycling activity.

More details on throughput, county distribution, emission factors and controls is provided in the following subsections.

(a) Activity Data / Throughput

The fugitive emissions and throughput from these facilities were used to estimate an emission factor. This emission factor along with reported throughputs from the smaller foundries and forging facilities within the District provided fugitive PM emissions from these sources.

District staff used an engineering analysis of fugitive PM emissions from a recent CEQA analysis conducted for a new facility in West Sacramento, California to estimate fugitive PM emissions from Bay Area scrap metal recycling facilities (Category 2223).

(b) County Distribution / Fractions

For point and area sources, information on the location of each facility was known and the emissions were distributed to the counties accordingly.

(c) Emission Factors

Point source emission factors may be source specific factors reported by the plants through source test results or derived from USEPA AP-42 emission factor.

The area source fugitive metal PM emission factor, 0.355 lbs/ton, for Category 2221 was derived from 2010 facilities’ emissions and annual throughput.

The area source fugitive metal PM emission factor, 0.0688 lbs/ton, for Category 2223 was based on the 2010 Schnitzer Steel and Sims Metal Management facilities’ emissions and annual throughput.

(d) Control Factors

In 1963-1970, the particulate emissions were reduced due to the control imposed by Ringlemann requirements from [Regulation 6]. Currently, there is an estimated 98.5% overall control of particulates from Category 34 and over 99% for Category 2222.

On May 1, 2013, District’s Rule 12-13, Foundry and Forging Operations, 48 was adopted. For Category 34, organics are reduced by approximately 42%, beginning May 1, 2015. For Category 2221, this rule reduces fugitive particulate emissions by approximately 10% through an Emission Minimization Plan, beginning May 1, 2015.

On May 1, 2013, District’s Rule 6-4, Metal recycling and Shredding Operations, 49 was adopted. For Category 2223, this rule reduces fugitive particulate emissions by approximately 24% through an Emission Minimization Plan, beginning May 1, 2015.

(e) Speciation

For area source categories 2221 and 2223, the Particulate Matter (PM) speciation profile was based on CARB’s speciation of PM for Secondary Metal Production 50.The PM10:PM ratio is equal to 0.633. The PM2.5:PM ratio is equal to 0.474.

4.6.3 Changes in Methodology

There are no changes to methodology for these Metallurgical, Foundry & Forging Operations; Metal Recycling & Shredding Operations (Categories 33, 2221, 2222, 2223).

4.6.4 Emissions

A summary of emissions by category, county, and year are available via the associated data dashboard for this inventory publication.

4.6.6 Uncertainties

The estimated emissions for Categories 2221 and 2223 based on larger foundries and forges within the District may contribute to an increased uncertainty of Metallurgical, Foundry & Forging Operations emissions from smaller facilities.

4.6.7 Contact

Author: Michael Nguyen

Reviewer: Ariana Husain

Last Update: November 06, 2023

4.6.8 References & Footnotes

  1. BAAQMD. 2013. Regulation 12 Rule 13 - Foundry and Forging Operations, https://www.baaqmd.gov/rules-and-compliance/rules/reg-12-rule-13--foundry-and-forging-operations↩︎

  2. BAAQMD. 2013. Regulation 6 Rule 4 - Metal Recycling and Shredding Operations, https://www.baaqmd.gov/rules-and-compliance/rules/reg-6-rule-4--metal-recycling-and-shredding-operations↩︎

  3. CARB. [accessed 2023 Feb 28]. CARB’s Speciation Profiles, https://ww2.arb.ca.gov/speciation-profiles-used-carb-modeling↩︎