EPA boiler MACT rules ease biomass pains

By Lisa Gibson | February 22, 2011

Drawing from about 5,000 public comments on its boiler Maximum Achievable Control Technology rules proposal released in April, the U.S. EPA has overhauled the standards for major and area source boilers, as well as solid waste and sewage sludge incinerators.

Released Feb. 23, the final draft of the MACT rules will reduce the cost of compliance by 50 percent compared with the proposal, the agency said, while achieving significant health benefits.

The new rules do include some flexibility for biomass boilers, said Gina McCarthy, an EPA assistant administrator. They combine biomass and coal boilers into one solid-fuel category, closing the loophole for other solid fuels and eliminating the requirement of biomass boilers to install scrubbers for certain pollutants the EPA found are not emitted heavily from biomass boilers, such as mercury and hydrogen chloride. That change, McCarthy said, is the biggest difference between the final and proposed rules and will save a large amount of money. The rule establishes numeric emissions limits for mercury, dioxin, particulate matter, hydrogen chloride and carbon monoxide.

As outlined in the final rules, existing area source biomass boilers—those that emit less than 10 tons per year of any single toxin or less than 25 tons per year of any combination of toxins—will be required to simply conduct tune ups rather than comply with numeric emission standards, McCarthy said. New area source biomass boilers with heat input 10 million Btu per hour or greater will be required to meet emission limits for particulate matter.

Technologies considered solid waste incinerators will still need to meet standards for nine pollutants—mercury, lead, cadmium, hydrogen chloride, particulate matter, carbon monoxide, dioxins/furans, nitrogen oxides, and sulfur oxides—but the rule clarifies that space heaters are not regulated by it. The definition of solid waste, which determines whether a technology will fall under boiler or incinerator rules, still specifies that in order to be considered a solid waste, a material must have been discarded in the first instance and meet legitimacy criteria for a solid fuel. So resonated wood residuals do not fall under the solid waste definition.

Finally sewage sludge incinerators will be required to adhere to emission limits for the same nine pollutants as solid waste incinerators.

The EPA had asked for a 15-month extension of its Jan.21 deadline for the final rule, citing the overwhelming number of comments, but only received one month. McCarthy said a lot of the changes to the final rule were a result of issues brought to light in those comments. While the 15-month extension would have allowed for a re-proposal and another comment period, the EPA will now essentially use the reconsideration period to solicit comments on certain aspects of the final rule, excluding anything related to sewage sludge incineration.

More information on the final rules, as well as specific solid waste classifications for certain biomass materials, can be found at http://www.epa.gov/airquality/combustion/actions.html#feb11.