The Western Lake Superior Sanitary District has applied to the MPCA to renew its existing air quality permit. The facility is located adjacent to an area where more than 40-percent of residents are part of a low-income household, which qualifies it as an environmental justice area.
The following fact sheet provides basic information about the facility and the proposal to reissue its air permit:
What is environmental justice?
The Minnesota Pollution Control Agency works to make sure that pollution does not have a disproportionate impact on any group of people. This is the principle of environmental justice (EJ). It means that everyone, regardless of race, color, national origin or income — receives equal levels of environmental protection and has opportunities to participate in decisions that may affect their environment or health.
As part of this commitment the MPCA has identified EJ communities in Minnesota. These are areas that have higher numbers of people of color or low income and communities within tribal boundaries. (The U.S. Environmental Protection Agency defines what designates an EJ area.) Some of these areas bear disproportionate burdens of pollution, and residents may want to participate in decisions about activities that the MPCA permits there.
To this end, the MPCA tries to notify EJ communities of environmental permits for facilities located in those communities. Usually this is done when new activities are proposed that would require permits, or when existing permits are modified or reissued.
What do they do?
WLSSD is a publicly owned treatment works whose primary function is to treat municipal and industrial wastewater. The facility also includes household hazardous waste collection. The facility generates about 200 tons of sewage sludge each day, which is currently treated with digesters that biologically decompose the sludge so it is stable for storage and application to land. The byproducts of anaerobic digestion are methane (CH4), carbon dioxide (CO2), and small amounts of nitrogen, hydrogen, hydrogen sulfide (H2S) and water.
What are their air emissions?
The facility emits a variety of pollutants including nitrogen oxides, carbon monoxide, and CO2 from combustion, and CO2, CH4, and H2S from anaerobic digestion. The gases from the digesters are routed to a combustion device. All of these pollutants are regulated under federal and/or state and laws and rules. The main regulated pollutants emitted from this facility are CO, volatile organic compounds, and CO2e (a group of gases that are functionally equivalent to CO2).
What is WLSSD proposing to do?
The digester gas must be burned to avoid releasing methane, a greenhouse gas, into the atmosphere. Currently, digester gas is burned in a flare or in heating boilers. WLSSD proposes to install three new generator engines to burn the gas. The engines will also be allowed to burn up to 90% natural gas to supplement the fuel value of the digester gas.
These engines were originally authorized in 2014, but were not built before that authorization expired in December of 2019. This project reauthorizes that construction, allows the engines to burn natural gas, and incorporates tighter limits on sulfur dioxide (SO2) from updated Minnesota rules. In order to meet the new limits, the digester gas will be treated to reduce its sulfur content before being burned in the engines.
Does the public have a say in air permit decisions?
Public participation is an important part of MPCA permitting decisions. Normally the MPCA seeks public input through a process of public notice and comment on draft permits, but permits in EJ areas may have additional public outreach before that step. Communities may request additional outreach by MPCA staff at any time during permit development.