DETROIT (WWJ) - Michigan regulators have approved a change to how two Marathon plants in the Motor City release sulfur dioxide emissions responsible for foul odors, officials said on Friday.
The Department of Environment, Great Lakes, and Energy (EGLE), Air Quality Division (AQD) said Marathon Petroleum Company (MPC) made the request so they could move some sulfur production from the East Plant Sulfur Recovery Unit to the newer, more efficient North Plant Sulfur Recovery Unit.
"The North Plant SRU operates more efficiently at converting sulfur compounds from sour water and acid gas streams to elemental sulfur," the company said in a project summary.
The change would reduce sulfur dioxide (SO2) emissions from the refinery, officials added.
Both plants play a role in transitioning chemical compounds containing sulfur into elemental sulfur, which is made into a product and sold.
EGLE officials approved the permit after a public comment period was held from June 22 to Aug. 10 -- it included a virtual informational session and public hearing.
According to the project report, the amount of pollution Marathon would be allowed to release will not change, but rather shift to the North plant if production is moved.
In detail, Marathon requested to remove the North plant's emission limit and implement a combined limit of 390 long tons per day between the two plants -- the East plant still remain at 130 long tons per day regardless, the EGLE said.
The North plant has an emissions limit of 100 parts per million by volume in comparison to the East plant's 175 parts per million.
According to the Center for Disease Control and Prevention, sulfur dioxide is a nonflammable, colorless gas with a very strong, pungent odor that many have described as smelling like burnt matches, skunk, rotten eggs, or natural gas.
Marathon said it can contribute to cleaner air and lower SO2 emissions by utilizing the North plant "when practicable to do so."
Southeast part of Michigan where Marathon operates the refineries has a history of failing to meet federal safety standards for SO2 and ozone in the air.