If it is ever built, it will be dirtier.

Texas-based Hyperion Refining LLC has altered its methane emission estimates on its proposed 400,000 barrel-a-day tar sands oil plant near the Iowa-South Dakota border.

It had previously omitted details about part of the refining process, reports the Sioux City Journal.

The company now expects the refinery to produce alsost twice as much methane – 980 tons per year instead of 498. That is significant, because as the Sioux City Journal reports:

Methane, an odorless gas, is considered a more potent greenhouse gas, trapping heat in the atmosphere at a rate 20 times greater than carbon dioxide over a 100-year period, according to the U.S. Environmental Protection Agency.

Hyperion said it had inadvertently left coke drum steam vents out of its original estimates to the South Dakota Department of Environment and Natural Resources. Continue reading →