What it means for Minneapolis to be green looks likely to be a point of contention in this year's mayoral contest -- or so it appeared Wednesday night at a seven-way candidates' debate sponsored by the League of Women Voters.

Three candidates -- Betsy Hodges, Cam Winton and Gary Schiff -- said that they would reject any additional garbage burning at the Hennepin Energy Recovery Center in downtown Minneapolis. Keeping the city's air clean demands it, they said.

Three more -- Mark Andrew, Jackie Cherryhomes and Don Samuels -- said they'd let the latest scientific research on the garbage burner's emissions be their guide. Andrew, a former Hennepin County commissioner, praised the burner as an electricity generator using non-fossil fuel. It's "the biggest and most successful alternative energy project in the history of the state." 

Jim Thomas, an educator who's new to the race, said that as mayor he would look for ways to export garbage to other facilities. 

Garbage wasn't the only issue that took on a green tinge at the debate. Environmental protection and sustainability were also themes in discussions of transit, economic development and population growth and density. 

A green thread also runs through two candidates' backgrounds. Winton, a political newcomer who says he won't seek any political party's endorsement, helped build a wind turbine maintenance company. Andrew heads an energy consulting firm for large public and private buildings. 

Andrew's stated intention to make Minneapolis the "greenest city in the United States" challenges him and every other candidate to explain what that goal means, how it might be attained, and how it relates to other urgent city business. Minneapolis needs a larger tax base, more affordable housing, more living-wage jobs, higher student achievement and slow-er growing property taxes. My guess is that voters will be more willing to think green if they can see how a pro-environmental agenda advances those goals.