Wall Street Journal: Replacing oil with home-grown biofuels is already proving to be an environmental headache for Washington. Fixing that could turn out to be an expensive headache, as well. Environmental groups Earth Track and Friends of the Earth just put out a study quantifying biofuels subsidies through 2022, as the U.S. plans to massively increase production of biofuels. The upshot? The cost to taxpayers would be about $420 billion over that period, or an average of about $28 billion a …