Both the Democratic and Republican national conventions are going green when it comes to cars. General Motors has been tagged to supply hundreds of cars that use E85, a mix of 85 percent ethanol. At the gop convention in Minneapolis-St. Paul in early September, the cars will run on "Freedom Fuel" from local suppliers, distributed at stations around the Twin Cities. And in Denver, where the Democrats meet in late August, the cars will chug on fuel made from beer waste from local Molson Coors Brewing Co. "This gives new meaning to 'Drive responsibly,' " says GM Washington spokesman Greg Martin. "The next time I crack one open after a hot day of yard work, I can tell my spouse I'm striking a blow for energy security."