collin peterson Photo illustration by Tom Twigg / GristLike a tractor inching through a wet field, the Waxman-Markey climate legislation slowed to a crawl last week, on the verge of getting stuck. The bill’s authors still have to deal with plenty of mud, but it’s now looking like they will get a vote by Friday of this week after all.

The main obstacle is still House Ag committee chief Collin Peterson (D-Minn.). About a month ago, Peterson warned anyone who would listen that he had de facto veto power over the historic climate bill. Unless the bill could be tailored to the specifications of Big Ag, he vowed, he would align his committee’s 26 Democrats to vote against the bill–likely a lethal blow. “We’ve thrown a pitchfork in the sand,” he declared.

Now he’s demonstrating that those threats weren’t idle; negotiations between Peterson and Henry Waxman continue even with the bill on the legislative calendar for later this week. As The Wall Street Journal recently put it:

The fate of the leading proposal to curb U.S. greenhouse-gas emissions is in the hands of Rep. Collin Peterson, a Marlboro-smoking free spirit who scoffs at warnings about climate change and says the Environmental Protection Agency is “in bed with” corporations opposed to the ethanol industry.

Peterson and Waxman reached some sort of provisional, tentative agreement late Monday. They have so far released no details, and have made clear that they have more to hash out before Friday’s vote. So what is the ag chief trying to accomplish? In short, to plunge a pitchfork into what’s left of the legislation’s power to curb greenhouse gas emissions. He wants more relief for coal-burning power plants in rural areas; assurances that government support for corn-based ethanol won’t dry up, even as its environmental liabilities become ever clearer; and finally, and perhaps most of all, he wants control over how carbon offsets are awarded to farmers.

The bottom line is this: climate legislation can only be effective it nudges industries toward less greenhouse-gas intensive practices; and Collin Peterson aims to make sure the agriculture industry’s practices change little if at all, climate be damned.

The offset issuse seems to be the main sticking point between Peterson and Waxman. As for the coal-fired-plant issue, “Waxman offered to give additional emission allowances to rural electric cooperatives,” the New York Times reported last week.

But the carbon-offset question has proven much more contentious. According to a Friday Reuters article, negotiations are breaking down over who gets to determine what practices merit offsets, and how much those offsets should be worth.As I reported two weeks ago, Peterson essentially wants the legislation to reward large-scale farmers to do what they’re already doing–i.e., deliver cash rewards without inspiring more environmentally benign farming practices. And Waxman’s having none of it, Reuters reports. “We’ve got to figure out a way that everyone is comfortable with the validity of offsets,” Waxman told the news agency.

And evidently, Peterson’s agenda isn’t passing muster. The key sticking point may be over which federal agency — the USDA or the EPA — gets to decide what practices qualify as offsets. As the bill is written now, the EPA would decide; Peterson strongly prefers complete control for the USDA.

According to the New York Times/ClimateWire, Waxman has floated the idea of a hybrid model that would “meld oversight between U.S. EPA in Washington and the Agriculture Department at the local level.” Peterson has so far refused to accept that proposal.

The chairman may be insisting on eliminating the EPA’s role in judging ag offsets for a very good reason: the agency recently released a relatively lowball estimate of much the ag-offset market is worth, suggesting that it sees little carbon-mitigating value in the kind of practices Peterson would like to see rewarded.

On the other hand, the Energy Information Administration recently estimated that ag offsets worth as much as $24 billion annually, the Wall Street Journal reports. That’s a titanic amount–more even than commodity subsidies in a bad year for crop prices. But that figure assumes a highly liberal accounting for what constitutes an ag offset. The chairman evidently hopes that the USDA is more likely than the EPA to deliver such generous accounting.

In short, if Peterson wins this battle, our nation’s first significant climate legislation will likely end up at worst rewarding, and at best not penalizing, chemical-intensive, greenhouse-gas-spewing agriculture. We will have bungled a major opportunity for positive change.

President Obama has yet to intervene in this battle. Now’s the time. Given that he’s a farm-state politician himself, am I being naive to hope that he comes down against the agribusiness interests intent on hijacking this bill?