OIL: Calling last week’s spill in Wisconsin “completely unacceptable,” the U.S. Department of Transportation denied permission for Enbridge to restart a major oil pipeline Tuesday. (Reuters)

WIND: The Romney campaign’s opposition to extending wind tax credits isn’t sitting well with Iowa Republicans – Gov. Terry Branstad used the opportunity to criticize both Romney and Obama for not recognizing the state’s wind industry “success story that is years in the making,” while Sen. Chuck Grassley posited that the campaign misspoke, “because [Romney] was over in Poland, he obviously wasn’t thinking about wind energy.” (Des Moines Register, The Hill)

MEANWHILE: FERC Chairman Jon Wellinghoff warns allowing the production tax credit to expire “could have a devastating effect” on the wind industry. (The Hill)

ALSO: A new study identifies locations across the northern Great Plains where wind turbines could be sited without significantly impacting wildlife habitat. (Greenwire)

BIOFUELS: As the summer’s heat puts the squeeze on corn farmers, researchers in Illinois are trying to unlock genetic secrets that could lead to more drought-tolerant biofuel crops. (Midwest Energy News)

COAL: An annual survey finds U.S. emissions of CO2 and other pollutants are falling as utilities switch from coal to natural gas; Midwest Generation, which operates six coal plants in Illinois, may file for bankruptcy; and NASCAR racer Dale Earnhardt, Jr. becomes a pitchman for “clean coal.” (Forbes, Chicago Tribune, Politico)

NATURAL GAS: Purdue University nears final approval for its plan to switch from coal to natural gas, and a utility that opted out of a Chicago coal-to-gas plant files for a rate increase. (Lafayette Journal & Courier, Chicago Tribune)

ETHANOL: Two of the largest ethanol producers in the U.S. reported lower earnings Tuesday. (Des Moines Register)

OIL SANDS: While the industry insists “dilbit” – the heavy crude from Canada’s oil sands that spilled from a Michigan pipeline two years ago – is no different than conventional crude, U.S. tax law has a different view. (InsideClimate News)

FRACKING: A poll finds 2/3 of Ohioans know very little, or nothing at all, about shale gas drilling. (Columbus Business First)

SOLAR: A suburban St. Louis district plans to install solar panels on five schools this year. (St. Louis Suburban Journals)

COMMENTARY: Grist’s David Roberts says Michigan’s decision on expanding its renewable energy standard is the most important clean-energy vote this year, and the Bismarck Tribune says a new assessment of North Dakota’s shale reserves justifies investment in capturing natural gas instead of flaring it.