More than 50 Democratic lawmakers on June 18 urged EPA Administrator Lee Zeldin to reverse a March agency proposal that would strip pyrolysis and gasification units from the Clean Air Act's definition of municipal waste combustion units.

Oregon Sen. Jeff Merkley and California Rep. Jared Huffman organized the letter, which targets a rule the Trump administration framed as regulatory relief for nascent plastics-to-feedstock projects. The lawmakers argue the proposal would exempt the two thermal processes from incinerator-grade permitting and emission limits even though both rely on high-temperature destruction of plastic feedstock rather than mechanical sorting.

What does the March proposal change?

The proposal would reclassify the two technologies out of the Clean Air Act's "municipal waste combustion unit" category and into a "manufacturing" classification with lighter federal oversight. Industry groups have pursued that reclassification for years as part of a campaign to expand chemical-recycling capacity in the United States.

The March filing, published in the Federal Register, follows a separate administration action to ease permitting for post-disaster incinerator deployment. Both moves reflect a broader Trump-era push, revived this term, to redefine plastic-waste processing as a manufacturing activity rather than a waste-handling one.

What do pyrolysis and gasification do with the plastic stream?

Pyrolysis heats plastic waste in the absence of oxygen; gasification heats it with controlled oxygen but below complete combustion. Both yield a hydrocarbon output marketed to refiners and polymer producers as a substitute for virgin naphtha or diesel.

Industry backers position the technologies as a destination for films, multilayers and other formats that mechanical recyclers routinely reject at material recovery facilities. Operating economics hinge on tipping fees, oil prices and the regulatory ceiling a given facility faces.

A manufacturing classification would lift Section 129 limits on dioxin, mercury and hydrogen chloride emissions that constrain municipal waste combustion units — a meaningful cost difference for projects currently in permitting.

Why are Democrats pushing back?

The coalition frames the reclassification as a loophole that opens municipal-scale plastic throughput to facilities operating outside the emission-control regime applied to waste-to-energy combustors. The letter asks EPA to withdraw the definitional change and continue treating pyrolysis and gasification units as municipal waste combustion units under the Clean Air Act.

The dispute centers on whether chemical recycling counts as waste processing or chemical manufacturing — a distinction with material consequences for permitting, public reporting and emission limits. Industry markets the technologies as "advanced" or "molecular" recycling; opponents describe them as incineration with an output-stream step.

Where does industry stand?

Plastics trade groups and individual pyrolysis developers have backed the manufacturing label in public comments, arguing that pyrolysis and gasification produce marketable fuels and chemical feedstocks.

The Trump administration has cast the two thermal processes as solutions for handling hard-to-recycle plastics — terminology industry groups have used for years to position chemical recycling as a complement to mechanical sorting at material recovery facilities.

What happens next?

EPA has no statutory deadline to respond to the congressional letter, but the agency must still finalize or withdraw the March proposal before the definitional change takes effect. Public comment closed in the spring, and industry submissions from plastics producers heavily favor the manufacturing classification.

The milestones to watch are EPA's final action on the March proposal, parallel state-level permitting decisions, and any litigation that follows a final rule. A finalized redefinition would reset the compliance baseline for every chemical-recycling permit issued afterward; a withdrawal would preserve the prior definitional framework through the next regulatory cycle.