U.S. EPA today finalized new air standards for backup generators that are typically used during emergency situations to keep power flowing and avoid blackouts.

The amendments to the National Emissions Standards for Hazardous Air Pollutants for reciprocating internal combustion engine, or RICE, generators will affect a broad swath of generators that may be used to power equipment in industrial and agricultural settings, including oil and gas production.

EPA's final amendments will reduce the 2010 rule's burden on industry. The capital investment required, EPA said, will be cut by $287 million and annual costs will be trimmed by $139 million.

Those cuts largely come from allowing dirty generators to operate for longer periods of time without installing pollution controls, a bone of contention for public health advocates. The standards will allow emergency generators to be used to prevent outages for 100 hours per year, significantly more than the current cap of 15 hours.

Demand response companies had asked EPA to raise the limit, saying they need more flexibility to ensure grid reliability and that the 15-hour cap was arbitrary.

EPA emphasized, however, that there will still be significant emissions reductions due to the standards. Particulate matter emissions will be cut by 2,800 tons per year, EPA said, as well as a 9,600-ton-per-year reduction in nitrogen oxide emissions. Emissions of carbon monoxide and volatile organic compounds will also be significantly trimmed, EPA said.

The agency also removed a provision from its proposal that allowed generators to operate for up to 50 hours per year during high demand periods, or "peak shaving," and other nonemergency situations through August 2017. That provision had been highly criticized by public health advocates, Democrats on Capitol Hill and even some trade groups (E&E Daily, Nov. 29, 2012).

Electric Power Supply Association (EPSA) President John Shelk called the revision a "big positive."

Frank O'Donnell of Clean Air Watch agreed that the final amendments are an improvement over the proposal because EPA is now requiring the generators to use low-sulfur diesel fuel, which burns cleaner.

"But it is still a loophole that will permit diesel generators to run without pollution controls," O'Donnell said. "Using pollution controls would mean lower emissions."

Shelk added that his group is still evaluating the final amendments and remains concerned that the 100-hour limit allows utilities to bid into markets using dirty generation.

"Dirty generation, therefore, is displacing cleaner, largely gas-fired power plants," he said. "This is going to make it harder for gas plants to compete in markets like PJM [Interconnection]."

The EPSA may consider litigation to address those issues, Shelk said.

Demand response companies, such as Boston's EnerNOC Inc., had pressed EPA to change the rules, arguing that the 15-hour limit was arbitrary. They also argued that the generators are only used as a "last line of defense," and groups like EPSA were overstating their use (Greenwire, May 29, 2012).