As the biomass industry sorts through pages upon pages of the U.S. EPA’s final Maximum Achievable Control Technology rules released in February, it’s safe to assume that many biomass boiler operators have numerous questions about how their operations will be affected specifically.

To answer those questions, the Biomass Thermal Energy Council held a webinar March 17 that summarized the rules, discussed studies surrounding emissions from forest and agriculture residues used for energy, and addressed specific control technologies. More than 250 people tuned in with questions about specific portions of the MACT rules, types of additional control technologies, and of course the 60-day reconsideration period that will open after the rules are published in the federal register later this month.

Speaker John Hinckley, principle consultant for Resource Systems Group Inc., discussed the study “Emission Controls for Small Wood-Fired Boilers,” conducted in conjunction with the Biomass Energy Resource Center. The study evaluated 24 stack test emission reports for wood chip and wood pellet systems, focusing on particulate matter (PM), comparing Europe’s controls to the U.S.’s, and looking at cost analyses. Hinckley said the study was done in response to public concerns about small wood-fired boilers.

Add-on emission controls include mechanical collectors, dry electrostatic precipitators (ESP), and baghouses or other fabric filters. In one analysis, Hinckley evaluates the effectiveness of reducing PM 2.5, PM 10 and overall PM with different controls. “I compared it to what I see in literature,” he said. Multicyclone systems paired with baghouse results were below his expectations, as were high-efficiency multicyclone, and single cyclone systems. But the use of two multicyclone systems in series met Hinckley’s expectations, his data showed. His overall results showed PM 10 can be controlled best with high-efficiency multicyclone systems, or a multicyclone process with a fabric filter. “I see that obviously no control will not help you get to [the level specified for small boilers in MACT], but also cyclone only will not get you down to that level either,” he said. The PM standard for small biomass boilers between 10 MMBtu and 30 MMBtu input is 0.07 pounds per MMBtu, he added.

The capital cost for installing baghouses versus ESPs for additional PM controls in units between 7 MMBtu and 12 MMBtu input are about the same, Hinckley said, contrary to popular opinion. “We’ve learned there are a lot of factors that affect emission control price,” he said.

The final MACT rules include standards for four source categories—major source industrial, commercial and institutional boilers and process heaters; area source industrial, commercial and institutional boilers; commercial and industrial solid waste incinerators; and sewage sludge incinerators—as well as an updated definition of solid waste, crucial in determining which rules a technology will fall under.

The biggest changes in the final rules include a new boiler category for solid fuels, which effectively makes many numeric emission limits for biomass boilers easier to meet. The rule also eliminates numeric emission standards for certain small biomass boilers.

Webinar speaker Jim Eddinger, of the EPA’s Energy Strategies Group, said the agency is reaching out to help facilities comply with the new rules. “We are looking at outreach for certain groups,” he said. The EPA, with the USDA, will be reaching out to biomass boilers affected by the rules, while the U.S. DOE will reach out to help coal and oil facilities, he said. The cost of compliance for the final rule is about $2 billion per year, half the estimated compliance cost for the proposed rules..