Illinois lawmakers approved a plan to build a massive natural gas plant on Chicago’s South Side. The project promises to create jobs, but may also increase both pollution and utility bills. The plant would turn Illinois coal and refinery waste into substitute natural gas, which four utilities would face strong pressure to buy. That gas would be pricey, which could drive up people’s bills.

“There’s no question that the gas coming out of this plant will be more expensive than the gas you can buy on the open market,” said Barry Matchett, co-legislative director at the Environmental Law and Policy Center. “It will be more expensive for at least 20 years. We think that’s grossly unfair.”

The project’s developer, New York-based Leucadia National Corporation, has pledged to put up money to offset the higher costs, though if gas prices stay near their current rates, that fund would be exhausted within several years.

Supporters say the plant has plenty of environmental and economic benefits, like redeveloping a South Side brownfield and creating 200 jobs. It would also provide a major customer for Illinois’s high-sulfur coal, which has few domestic markets left.

The bill passed by veto-proof margins, and now awaits the governor’s signature.