Burning more of Minnesota's garbage and putting less in landfills has been the state's goal for years, but every day in Elk River, full garbage trucks rumble past a garbage-to-energy recycling center to dump their contents at the landfill next door.

Last year alone, an extra 140,000 tons of waste from the metro area went into landfills, which are cheaper for haulers, instead of the more environmentally friendly burners.

But the state is getting ready to crack down on the practice. Next month it will start forcing haulers to use the metro area's four waste-to-energy burners to their full capacity and make old-fashioned landfills, which leave a destructive environmental legacy for decades, an option of last resort.

It's part of a push to wean the state off its stubborn reliance on landfills, which remain the destination for about 25 percent of the metro area's trash. The rest is burned, recycled or otherwise processed.

"Landfills serving the metropolitan area ... are going to fill up someday, and that capacity really needs to be restricted to the stuff that we can't recycle or can't use for energy," said Sigurd Scheurle, sustainable materials manager for the Minnesota Pollution Control Agency (MPCA).

In 1991, only about 10 percent of metro garbage went to landfills, and state officials are pushing aggressive new goals that get landfill use back down to that level or lower by increasing recycling and other forms of waste processing. Landfill use jumped between 1991 and 2002 because of population growth and economic expansion, officials say.

The metro area has three landfills for garbage -- in Elk River, Burnsville and Inver Grove Heights -- and four waste-processing centers, in Minneapolis, Elk River, Newport and Red Wing.

Starting in mid-February, only when the processing centers are full -- and receiving enough garbage to allow them to operate at their maximum energy-producing capacity -- will it be legal for haulers to take trash to a dump.

The MPCA is wading into the privately owned garbage system in part because the metro area has an unusually large number of private haulers who are all looking for the cheapest disposal they can find to keep their prices competitive.

The MPCA does not expect the new requirement, which has been written into law for years but not enforced, to be a problem for the haulers.

"For the better part of 20 years, waste haulers, both large and small, have had delivery contracts with resource recovery facilities," Scheurle said. "I don't think there will be any mystery for people in the business to figure this out."

Waste Management, which operates the Burnsville landfill, supports the processing of garbage, said spokeswoman Julie Ketchum. But, she said, "We don't want to be put in the position of enforcing the law" at the landfill.

Local trash hauler Garbage Man, which calls itself a "green company," estimates that more than 75 percent of the garbage its haulers collect already goes to energy-recovery centers.

"It's a law I definitely approve of," said Jason Hartman, human resources director.

Millions of tons

In 2011, the metro area generated about 3 million tons of municipal solid waste, and about 800,000 tons went to landfills.

Tipping fees at the landfills -- which are privately owned -- are lower than at energy-recovery centers because the processing centers remove recyclables and use state-of-the-art pollution control equipment to produce renewable energy.

Redirecting 140,000 tons of waste is significant, said Trudy Richter, executive director of the Minnesota Resource Recovery Association. "It makes a big difference in the amount of renewable energy we are producing and in the amount of recyclables we are getting out of the waste."

It has been the state's goal since 1980 to reduce landfilling, because buried waste can pollute groundwater, send off gases that contribute to global warming and occupy land that could be put to more desirable use.

To reduce landfill use, the MPCA in 2010 set out aggressive new goals for recycling.

"We are making a more concerted effort to improve solid waste management in the state and ensuring that the waste is used in a way that's better than just landfilling it," said Tina Patton, MPCA solid waste planner.

The seven metro counties say they applaud the decision to force garbage to the reprocessing centers.

The environmental superiority of burning is clear, said Carl Michaud, director of environmental services for Hennepin County.

With the Hennepin Energy Recovery Center in downtown Minneapolis, Hennepin County turns garbage that remains after recycling into heat that warms the downtown Minneapolis heating district and into electricity, which it sells to help pay for recycling programs, Michaud said.

Ash from the burner can be disposed of in a landfill without causing environmental problems for future generations, he said. "From our perspective, the whole idea of processing is good," Michaud said.