POWER¦
on account of environmental group appeals. “They challenged all of our BACT decisions, air permits and how we calculated emissions, but we won it all.” Mogan reiterates the significance of factoring in technical feasibility, as one of his clients working to install a 6-MW biomass boiler to supply process heat for the greenhouses at their facility, and was required to perform a BACT Analysis for PM, PM10, NOx, and CO. One of the control devices identified for the control of PM was a baghouse, which are typically installed on larger units at facilities that have full-time boiler staff to monitor potential fire or safety issues. The greenhouse, however, did not have such a staff member. “It was deemed technically unfeasible from that standpoint,” Mogan says. “In our case, the secondary controls scenario, an ESP was very close in terms of control efficiency. “ During the BACT determination process, the U.S. EPA’s BACT Clearinghouse database provides helpful guidance, as it is a publically available collection of BACT and other technology-based decisions. However, problems may arise when permit limits representing a different project’s BACT decision are posted, and a similar project chooses those limits without doing proper due diligence. “A lot of times those plants aren’t even built—largely because they can’t meet those limits,” Morrison says. “[Clearinghouse posts] don’t establish a valid basis for a BACT decision, though that’s the way it’s done in a lot of instances. For example, one might find a 0.01 NOx limit in Vermont, and try to meet that. But taking a closer look, that plant in Vermont never got built, or it just started operating, and has no data to show it can actually comply with that limit. Going to the BACT Clearinghouse and cherry-picking out the lowest limit for each pollutant isn’t a good permitting practice—it will result in plants that don’t get built.” Furthermore, emissions from one source should not be compared to another source. “An example with biomass is—and this is evident when you look at the Boiler MACT rules—different emission limits are set for different types of boilers,” Morrison says. “A vibrating grate stoker boiler has a very different emissions profile than a fluidized bed boiler, so if your choice is to install a grate-fed stoker boiler, you have to be real careful about using emissions profiles from one to set BACT. If your design is to build a coal-fired power plant, you don’t set BACT on the level of emissions that a natural gas plant is able to meet. Environmental groups will try to do this to drive your emissions limit as low as possible—cherry-pick low emissions profiles from other types of sources and try to get them imposed on your project.” Mogan emphasizes the importance of site-specific analyses for BACT. “It might turn out that because of the size of your emission source, or an existing source that you’re modifying, it will cost more to knock down trees to make a whole new pad for the control device, thus rendering it uneconomically feasible.” And vendor quotes generally provide generic numbers, rather than site-specific. “That [vendor quote] should be used as a starting point, and site-specific engineering and land costs should be added in,” Mogan says. “It’s your property—you know where your control device needs to sit, and that will dictate how much duct and piping you need to install. Or maybe you already have a pollution control system for your plant and you need to figure out what type of new equipment you’ll need to integrate new control system. These may be big factors in overall economic feasibility [of BACT solutions].” Author: Anna Simet Managing Editor, Biomass Magazine asimet@bbiinternational.com 701-738-4961
AUGUST 2014 | BIOMASS MAGAZINE 17