EPA Subpart RRR compliance for Aluminum Recyclers

What is Subpart RRR?

Subpart RRR (40 CFR Part 63, Subpart RRR) is the US EPA's National Emission Standards for Hazardous Air Pollutants (NESHAP) for secondary aluminum production. It limits particulate matter (PM), hydrogen chloride (HCl), hydrogen fluoride (HF), dioxins and furans (D/F), and total hydrocarbons (THC) from scrap processing, melting, fluxing and dross operations at aluminum recycling plants.

The emission limits get most of the attention, but many compliance problems start upstream of the stack. A furnace meets its limits only if the fume is captured at the hood carried through the duct and treated in a collector sized for the plants current scrap mix. That makes dust and fume extraction the part of the system that often decides whether a plant passes its next performance test.

This guide covers the rule applies to, where compliance pressure is building for recyclers, and what a well-designed extraction system needs to deliver.

Who does Subpart RRR apply to?

Subpart RR applies to any facility that uses clean charge, aluminum scrap or dross as a raw material and performs at least 1 of these processes: scrap shredding; scrap drying, de lacquering or decoding; thermal chip drying; furnace operations such as melting, holding, sweating, refining, flexing or alloying; dross recovery; inline fluxing; or dross cooling (40 CFR 63.1503).

What a plant must do depends on its hazardous air pollutant (HAP) status:

Major sources must meet the full set of limits for PM, HCl, HF, D/F and THC across shredders, dryers and kilns, furnaces, dross equipment and secondary aluminum process units (SAPUs).

Area sources are subject only to the D/F requirements, and only for specific units, including SAPUs with Group 1 furnaces that process anything other than the clean charge.

The foundry and die caster exemption

Aluminum foundries, die casters and extruders are not treated as secondary aluminum production facilities if they melt only clean charge, customer returns or internal scrap, and do not operate sweat furnaces, thermal chip dryers, or scrap dryers, delacquering kilns or decoating kilns.

That exemption is lost in two common ways. The first is buying contaminated scrap from outside the company: internal scrap qualifies regardless of contamination, but only while it stays within the control of the company that produced it. The second is installing one of the listed thermal units. One narrow carve-out applies: an area-source foundry covered only because it runs a thermal chip dryer does not bring its furnaces under the rule, as long as those furnaces melt only clean charge, internal scrap or customer returns.

Group 1 vs. Group 2 furnaces

A furnace's group decides whether it carries emission limits, and two things set the group: what goes into the furnace and how it is fluxed.

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Two details move furnaces between groups. First, reactive fluxing means any flux other than cover flux that produces a HAP emission. Chlorine degassing or demagging therefore turns a clean-charge furnace into a Group 1 furnace, while argon and nitrogen are not reactive.

Second, the definition of clean charge covers more than ingot and sow. It includes scrap dried at 650F (343C) or higher, scrap delacquered or decoated at 900F (482C) or higher, and runaround scrap free of paint or coatings. Anodized aluminum with dyes or sealants containing organic compounds is not clean charge (40 CRF 63.1503). The performance of a decoating kiln directly affects how much contamination reaches the furnaces downstream.

Five places Subpart RRR compliance comes under pressure

Most established recyclers already operate permitted, tested systems. The risk is not routine operations, it's change. These five pressure points are where a dust and fume collection system that passed the last time can fall behind.

1. New capacity brings new obligations
   A new SAPU is any combination of Group 1 furnaces and in-line fluxers constructed or reconstructed after February 11, 1999 (40 CFR 63.1503). New furnaces need initial performance testing, and their emissions must fit within the SAPU calculation. Capture and control equipment is usually specified well before the furnace starts up, so emission control belongs in the project from the first design review.
2. Dirtier scrap changes the load on the collector
   Recyclers are taking in more post-consumer scrap, including used beverage cans and coated automotive material. More paint, lacquer and oil means more organics to destroy and more chlorine-driven chemistry in the furnace. That raises the acid gas and D/F load on a baghouse originally sized for cleaner feed.
3. Capture efficiency is a compliance requierment
   Subpart RRR ties capture and collection to the ACGIH Industrial Ventilation guidelines. Since the 2015 amendments, performance tests also require temportary hooding that meets those guidelines, or a petition filed 180 days before the test if hooding is impractical (ALL4 summary of the 2015 amendments). Fume that escapes at charging doors, sidewells or skimming is never measured at the stack, but it is a test-day and inspection risk.
4. There is no startup and shutdown exemption
   The 2015 final rule removed the separate startup, shutdown and malfunction provisions. Emission limits now apply during startup and shutdown, with their own compliance demonstration requirements, and the SSM plan requirement is gone. The extraction and control system has to be running and stable before the furnace is.
5. Operating headroom is production headroom
   Operating limits are set during the performance test and then monitored continuously. Typical parameters include lime injection rate, baghouse inlet temperature, reactive flux injection rate and bag leak detection alarms. A collector running at the edge of its capacity effectively caps how much flux a plant can use and how much metal it can push through.

Matching each affected source to its extraction and control approach

Each Subpart RRR affected source has its own pollutant profile, so each needs its own capture point and control approach. This table summarizes common practic; the right design for a given plant depends on its permit, its scrap mix and its existing equipment.

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For reference, the Group 1