On May 10, 2004, the Massachusetts Department of Environmental Protection (the Department) issued proposed rules that would regulate air emissions from small engines and generators. While the proposed rules would establish certainty and streamline the permit process for entities proposing to install certain renewable energy, distributed generation and emergency generation projects in Massachusetts, some of the emission limits established for larger generation projects likely cannot be met using existing or reasonably foreseeable emission control technologies.

The Department's proposal would establish stringent limits (which would decrease over time) for emissions of air pollutants from a wide variety of small engines and turbines–including all turbines with a rated output of less than 10 MW, as well as engines and turbines used solely on an "emergency" basis. The limits would be mandatory, and the ability of an individual project to seek an "exemption" from the requirements (by filing an application for an individual permit) would be restricted to certain types of projects (such as peaking power production, energy assistance program, natural gas compressor station and landfill gas-to-energy generation units). In addition, all new and existing liquid fueled engines and turbines covered by the proposed rules would be required to burn Ultra Low Sulfur Diesel (15 ppm) beginning no later than 2006.

The proposed rules are similar to those that the Department shared with a small group of stakeholders in September 2003. To the Department's credit, it incorporated many of the suggestions made by those stakeholders, such as expanding the definition of "emergency" conditions and setting emission limits for emergency generators and turbines which correspond to those established by EPA's non-road engine emission limits at 40 CFR Part 89. However, the Department did not respond to several requests that it prepare and circulate along with the rules a Best Available Control Technology (BACT) analysis to support the stringent emission limits contained in the proposed rules.

Although a step in the right direction, the Department's proposal is still likely to adversely impact industry and commerce within the Commonwealth, as well as impede the development of new renewable energy projects. Public hearings on the Department's proposed rules are scheduled for June 22 in Boston and June 23 in Springfield, and the Department will accept written comments until June 30.