State officials can penalize Twin Cities landfills for accepting garbage that could have been burned instead, an appeals court ruled Monday.

The ruling bolsters the Minnesota Pollution Control Agency’s effort to enforce a 30-year-old state law prioritizing burning the Metro area’s garbage vs. burying it. Landfills owned by the nation’s largest trash firms, Waste Management and Republic Services, sued the state in 2017 after the agency fined them.

When the state began enforcing the law several years ago, a garbage burner operated by Great River Energy in Elk River was starved for trash to fuel its power plant. That facility closed earlier this year, however, leaving the practical impact of Monday’s ruling unclear.

The ruling reverses a 2018 district court decision finding that the Minnesota Pollution Control Agency (MPCA) had overstepped its bounds by fining the landfills for accepting burnable garbage. Representatives for Republic, whose lawsuit reached the appeals court, declined to comment Monday.

The appeals court found that the MPCA had the authority to issue fines to the landfills for not complying with the law. But it stopped short of agreeing with the agency’s $20,000 fine on Republic’s Pine Bend Landfill in Inver Grove Heights.

A “genuine issue of material fact remains regarding the seriousness of the violation and whether the penalty was justified,” the ruling said. The ruling said a lower court should consider that issue.

The trash firms have argued it is difficult to comply with the law since haulers are regularly delivering loads of garbage to the landfills, and workers there do not know in real time whether the garbage burners need more material.

About a quarter of the metro area’s waste is currently landfilled, while another 29 percent is sent to garbage burners, according to the MPCA.

Most of the nonrecyclable trash in Minneapolis is sent to Hennepin County’s incinerator beside Target Field, which generally runs at its permitted capacity. Ramsey and Washington counties now require haulers to take trash to a processing center in Newport, which removes recyclables before sending the leftover material to Xcel Energy’s burners.