EPA to revise emissions formula for refinery flares

OREANDA-NEWS. October 14, 2016.  The US Environmental Protection Agency (EPA) plans to revise a key formula used to estimate the amount of emissions produced by flares at refineries and chemical plants.

The formula change would increase by 16pc the "emission factors" used to estimate the amount of volatile organic compounds (VOCs) produced by those flares, which refineries and chemical plants use to burn off waste gas and other hydrocarbons. EPA also committed to another change in response to concerns about the combustion efficiency of flares.

Those changes are in response to a lawsuit from environmentalists that said EPA was underestimating the amount of VOCs produced by flares, exposing nearby communities to more emissions than official estimates showed. Emission factors provide a way for industrial sources to estimate their emissions, which state and federal regulators can then use to determine the stringency of emission controls.

EPA just last year revised its emission factors for the same flares. That update said that for each 1 mmBtu of hydrocarbons that refineries and chemical plants route through flares, an estimated 0.57 pounds of VOC would be produced, or about four times higher than the agency previously estimated.

But environmentalists filed a lawsuit that argued the emission factors were still flawed. EPA in response reached a settlement, released today, where it agreed to increase the VOC emission factor for flares to 0.66 lb/mmBtu, or 16pc higher than the previous emission factor. EPA said this was a "technical correction" caused by an error related to the molecular weight of individuals compounds that comprise VOCs.

EPA today also agreed to add language to its regulatory documents that would say gases routed to flares should have a heat content of at least 270 Btu/ft3 to produce accurate emission factors. This would resolve concerns about a practice where refineries have injected steam into flares, reducing their combustion efficiency below the assumed 98pc and producing higher levels of emissions.

"These destruction efficiencies are so great at this point that there is a massive difference between 95pc and 98pc," Air Alliance Houston executive director Adrian Shelley said. His nonprofit was among the groups that filed the lawsuit challenging the emission factors.

EPA will accept public comment on the settlement agreement for 30 days. The changes will go into effect unless the agency receives comments indicating problems with the settlement.

Industry groups did not have an immediate reaction. The American Petroleum Institute's regulatory affairs director Howard Feldman said the trade group would carefully review the changes and "provide appropriate feedback, if necessary," but said it supports the use of best science and technology.