Potential Air Pollutant Emissions and Permitting Classifications for Two Biorefinery Process Designs in the United States.

Advanced biofuel production facilities (biorefineries), such as those envisioned by the United States (U.S.) Renewable Fuel Standard and U.S. Department of Energy's research and development programs, often lack historical air pollutant emissions data, which can pose challenges for obtaining air emission permits that are required for construction and operation. To help fill this knowledge gap, we perform a thorough regulatory analysis and use engineering process designs to assess the applicability of federal air regulations and quantify air pollutant emissions for two feasibility-level biorefinery designs. We find that without additional emission-control technologies both biorefineries would likely be required to obtain major source permits under the Clean Air Act's New Source Review program. The permitting classification (so-called "major" or "minor") has implications for the time and effort required for permitting and therefore affects the cost of capital and the fuel selling price. Consequently, we explore additional technically feasible emission-control technologies and process modifications that have the potential to reduce emissions to achieve a minor source permitting classification. Our analysis of air pollutant emissions and controls can assist biorefinery developers with the air permitting process and inform regulatory agencies about potential permitting pathways for novel biorefinery designs.