Brent Deppe is taking me on a tour of the farm supply business, called Key Cooperative, that he helps to manage in Grinnell, Iowa. We step though the back door of one warehouse, and our view of the sky is blocked by a gigantic round storage tank, painted white.
"This is the liquid nitrogen tank," Deppe explains. "It's a million-and-a-half gallon tank."
Nitrogen is the essential ingredient for growing corn and most other crops. Farmers around here spread it on their fields by the truckload.
"How much nitrogen goes out of here in a year?" I ask.
Deppe pauses, reluctant to share trade secrets. "Not enough," he eventually says with a smile. "Because I'm in sales."
For the environment, though, the answer is: Way too much.
The problems with nitrogen fertilizer start at its creation, which involves burning lots of fossil fuels. Then, when farmers spread it on their fields, it tends not to stay where it belongs. Rainfall washes some of it into streams and lakes, and bacteria in the soil feed on what's left, releasing a powerful greenhouse gas called nitrous oxide.
There have been lots of attempts to control renegade nitrogen. Most have focused on threats to water and wildlife. Maryland, Virginia and Pennsylvania, for instance, have spent billions of dollars keeping nitrogen (and other forms of fertilizer runoff) out of the Chesapeake Bay.
Reducing nitrogen's contribution to global warming, though, is even more difficult. Philip Robertson, a researcher at Michigan State University who's studied those greenhouse emissions, says that "ultimately, the best predictor of the amount of nitrous oxide emitted to the atmosphere is the rate at which we apply nitrogen." Essentially, the only proven way to cut heat-trapping emissions from nitrogen fertilizer is to use less of it. Most farmers haven't been willing to do this, because it could cut into their profits.
Enter the SUSTAIN program, which some food companies, including Walmart, are touting as a step toward the breaking this stalemate, allowing farmers to reduce their greenhouse gas emissions without reducing their profits. Land O'Lakes, one of the largest agricultural businesses in the country, runs SUSTAIN. It has made a pledge to Walmart to enrolls 20 million acres of farmland in the program, as part of Walmart's plan to reduce greenhouse gas emissions. "Land O'Lakes is a company that goes from farmer to consumer," says Matt Carstens, the executive in charge of it. "We have an obligation and an opportunity to do what's right."
I came to Key Cooperative to see what SUSTAIN looks like in practice.
I met Ben Lauden, a farmer who enrolled his acres of corn and soybeans in the program. Since signing up, Lauden has been doing a few things differently. He's applying nitrogen fertilizer several times during the growing season, instead of all at once. That's so the fertilizer arrives when the growing corn plants need it, and less is wasted. He buys "stabilizers" — chemicals that are mixed with nitrogen and keep it from washing away so quickly. Also, data on his fertilizer use goes into a computer program that monitors the weather and predicts how much nitrogen will remain in the soil.
It's all intended to let him use nitrogen more efficiently. But is he actually using less of it? Lauden pauses. "I think you would use less, but I don't — I can't quantify it, I guess," he says.
That's more or less what Michigan State researcher Philip Robertson has observed. The technologies that Key Cooperative is selling to Lauden, "if used properly, should allow the farmer to use less nitrogen fertilizer," Robertson says. But he adds, "whether that actually happens is the $64,000 question, because there are lots of cases where farmers have been sold stabilizers without necessarily recommending a reduction in the rate of fertilizer application."
Even Matt Carstens, who created SUSTAIN and promoted it to food companies and environmental groups, isn't promising that it will reduce the amount of nitrogen released into the environment. He does believe that it will help farmers use it more efficiently, allowing them to grow more corn without using more fertilizer. "There's definitely a trend in the direction of using [nitrogen] more wisely," he says. "But to say that every year we can count on a reduction, that's just not possible."
In fact, there's even some confusion about what SUSTAIN is supposed to accomplish. Brent Deppe, the manager at Key Cooperative, says that the program was introduced to him and to farmers as a way to tell consumers about the steps farmers are taking to protect the environment. "The message wasn't being told," Deppe says. "We're doing a lot of the right things. We just aren't advertising it."
SUSTAIN does not advise farmers to do anything as dramatic as growing different crops. And according to some environmentalists, that's exactly the problem. Careful management of fertilizer "is a good thing to do, but it's not enough," says Matt Liebman, a professor at Iowa State University.
Sarah Carlson, who works for an environmentally minded group called Practical Farmers of Iowa, has confronted Walmart executives about SUSTAIN and its limited goals. "I was like, 'Why are you only focused on nitrogen fertilizer management?" Carlson says. "That makes such little impact on water quality, and such little impact on greenhouse gas reduction."
Carlson has a counter-proposal. It sounds simple: Companies could give farmers a financial incentive to move away from simply growing corn and soybeans, instead adding "small grains" like oats (or rye) to their mix of crops.
That simple move could cut greenhouse gas emissions by a third, much more than anything SUSTAIN is doing, she says. Oats, unlike corn or soybeans, can easily be grown together with a "cover crop" of clover. That clover has an important benefit: It adds nitrogen to the soil the organic way, replacing the need for synthetic nitrogen that's manufactured in energy-intensive factories. (Nitrogen from clover still gets converted into nitrous oxide by soil bacteria, however.) In addition, cover crops add carbon to the soil, which also helps fight climate change.
Many farmers would be happy to do this, Carlson says. They understand the environmental benefits. But right now, those farmers don't have a market for those oats.
"You know, Walmart, you should suggest to your commodity buyers that they buy more small grains [like oats] for feed rations" for animals like pigs," Carlson says. "We have all these pigs in the state; 5 percent of their diet could be oats. We can just sprinkle it in there. It wouldn't be that hard."
There is, however, one crucial obstacle: Relying on oats for your bacon would cost a little more money, and somebody would have to pick up that tab. It could be Walmart — and, in turn, American consumers.
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