Minneapolis planning commissioners signaled informally Monday that they may set a no-net-increase requirement for pollution from the downtown incinerator if they decide to allow it to burn more trash.

The commission didn't act on the request Monday evening after hearing from burner opponents and operator Covanta Energy Corp., but asked for more information on emissions and health effects. The incinerator is next door to the new Minnesota Twins ballpark, which opens next spring.

Covanta and Hennepin County, for which it operates the incinerator, are seeking permission to burn an average of 1,212 tons of trash daily. The limit in the city's original 1987 zoning conditions for the facility is 1,000 tons per day.

Council Member Gary Schiff, who urged the postponement to June 22 adopted by commissioners, said the commission needs more baseline emissions data before setting a no-net-increase pollution limit as requested by the North Loop neighborhood.

Jeffrey Hahn, Covanta's environmental director, said the facility operates well within limits set in its state permit. Burning more garbage would produce an "insignificant increase" in regulated pollutants, except for nitrogen oxide, which the company thinks can be reduced with added controls, he said.

Although Covanta is seeking a 21 percent increase in the amount of trash it may burn, officials said the actual increase probably would be about 11 percent because of maintenance needs.

Opponent Al Muller told the commission that at current emission levels, the added tonnage Covanta wants to burn would add about 800 pounds of pollutants per day.

Commission member Lauren Huynh proposed the no-net-increase requirement to meet the zoning code standard that the proposal won't be detrimental to public health.

Carl Michaud, the county's environmental services director, said that burning more trash would produce more steam for heating county and downtown buildings, saving roughly $1.5 million in fossil fuel costs.

Ballpark environmental studies have found no added adverse impacts from burning the amount of trash Covanta wants to burn. But opponents of its request said that the impact on downwind neighborhoods and the cumulative impact of a variety of pollutant sources should be considered.

Among the questions that commissioners are seeking more information on is whether they can set stricter limits on the facility's emissions than set by its state permit or federal standards.

Steve Brandt • 612-673-4438