The environmental value of corn ethanol got a ringing endorsement Thursday from EPA chief Stephen Johnson.

Johnson declined a request to cut the Renewable Fuel Standard embedded in the 2007 Energy Act. The RFS mandates 9 billion gallons of corn-based ethanol be blended into the fuel supply this year, rising steadily to 15 billion gallons by 2015, and then holding steady at 15 billion gallons until 2022.

To produce 9 billion gallons this year, ethanol makers will churn through about a third of the U.S. corn crop. If corn production holds steady through 2015 — not an unreasonable assumption, considering that it’s already pretty much maxed out — we’ll be turning 55 percent of the U.S. corn crop into car fuel within seven years.

Consider that the U.S produces about 40 percent of the world’s corn — more than any other nation by a wide margin. The U.S. mandate has been pretty definitively linked to a rise in global food prices that could push 100 million additional people into poverty conditions.

Consider also that corn is an extremely heavy user of synthetic nitrogen fertilizer, which emits a greenhouse gas called nitrous oxide. The EPA itself terms nitrous oxide a greenhouse gas "about 310 times more powerful than carbon dioxide."

Finally, consider that every gallon of ethanol that gets mixed into the fuel supply costs taxpayers $0.51. Given the mounting challenges of climate change and energy scarcity, do we really have $4.5 billion-$7.5 billion to drop on a program that most serious people consider environmentally worthless, at best?

Yet the EPA’s Johnson can see nothing wrong with this wild-eyed rush to turn half of the corn crop into car fuel.  Here’s what he declared in a press release upholding the RFS:

The RFS remains an important tool in our ongoing efforts to reduce America’s greenhouse gas emissions and lessen our dependence on foreign oil, in aggressive yet practical ways.

Riiiiight. Of course, getting a ringing endorsement from Johnson on environmental grounds is like having Al Capone sign off on the legality of your gun-running operation. Guy’s got a bit of a credibility problem.

Of course, no one really challenged the RFS on environmental grounds. Texas Gov. Rick Perry (R) requested the RFS waiver on economic grounds — specifically, on grounds that higher corn prices are crimping the profits of industrial meat producers.

"Governor Hairdo," as he’s known in certain Austin circles, learned crony capitalism at the knee of his predecessor, Goerge W. Bush. And Perry evidently learned well. From the Houston Chronicle:

Poultry producer Lonnie "Bo" Pilgrim spent more than $9,000 on airfare in June so Gov. Rick Perry could attend a news conference promoting a waiver from federal ethanol mandates that Pilgrim wants.

Perry requested the waiver from the federal Environmental Protection Agency in April after meeting with Pilgrim in March. The Houston Chronicle reported this month that six days after that March meeting, Pilgrim donated $100,000 to the Republican Governors Association, which Perry heads as chairman.

This is one of those pox-on-all-your-houses deals. Yes, we need to gut the RFS. Turning half the U.S. corn crop into car fuel is insane. But we also need to rein in the vast environmental abuses of industrial-meat giants like Pilgrim’s Pride.