President Bush’s recent pledge to raise the Renewable Fuel Standard to 35 billion gallons by 2017 dropped with a bit of a thud.

David Roberts made a pretty good case that all the recent hype around ethanol may soon prove quaint: that, in essence, the ethanol craze will eventually likely crumble under its weighty political, agricultural, and technological contradictions. Maybe so.

Meanwhile, though, farmers are planting a shitload of corn, dozens of ethanol plants are sprouting up across the land, and the government is planning to plow ever more cash into research on cellulosic ethanol, a technology whose commercial viability remains perpetually five years away. It’s worth asking: If Bush’s ethanol dream did come true, how much would it cost taxpayers?

Answer: at least $118 billion.

That calculation comes from Gristmill’s own Ron Steenblik, research director of the Global Subsidies Initiative, and Doug Koplow, whose ground-breaking report on biofuel subsidies so informed Grist’s recent biofuels series.

And what would taxpayers get for that not inconsiderable chunk of change (which could theoretically be spent, say, building out high-speed trains between population centers)?

That’s a question of some debate. Researchers in Oregon recently looked at what environmental gains ethanol subsidies deliver for their own state, and concluded: not much.

For one thing …

the cost of reducing greenhouse gas emissions by switching to corn-based ethanol was calculated to be more than 200 times higher than other existing policy options to reduce greenhouse gas emissions.

For example?

For comparison, the authors calculated that the net energy benefits from increasing automobile fuel efficiency by one mile per gallon would be equivalent to three or four corn ethanol plants or 13 biodiesel plants

Ouch.