University of Minnesota

Winds of change

A novel approach in west central Minnesota is using wind turbines to create fertilizer, reducing fossil-fuel consumption in agriculture.

November 5, 2013

On a glacial ridge overlooking the U's greenest campus, two 1.65-megawatt wind turbines generate renewable electricity for the college and the region. Stand at the top of the hill, and you can hear the wind whistling; to U of M researchers at the U's West Central Research and Outreach Center nearby, it's the sound of opportunity.

In mid-July, the center officially launched a process believed to be one-of-a-kind, which takes the energy from wind, converts it to hydrogen, and then to ammonia that can be used as fertilizer on surrounding farmlands. The processing plant is part of the center's larger efforts to reduce fossil-fuel consumption in agriculture over the next 5 to 10 years, says Mike Reese, director of renewable energy research at the center and project lead.

An added benefit

One of the greatest barriers to wind power is the problem of storage. If the wind blows overnight, for example, when electricity demand is low, then storing that wind energy by creating hydrogen allows flexibility to produce other things like fertilizer, says Reese.

Capturing wind

The final pieces of the puzzle were locked into place with the installation of equipment that takes nitrogen from the air, combines it with hydrogen from the plant and makes anhydrous ammonia that can be used to fertilize farm fields. The typical "steam methane reformer" method, says Reese, uses natural gas to separate carbon and hydrogen in a process that may ultimately prove more costly and less efficient than the center's new facility.

Here, the process takes place in two sheds in a fenced-in area near the wind turbine marked "ammonia production room" and "hydrogen production room." Inside the ammonia room, a series of pipes and gauges connect to a tall, pressurized reactor where the chemical conversion takes place.

The pipes bring in hydrogen and nitrogen under high pressure, mix the gases, preheat them to 800 degrees Fahrenheit and then send them into a reactor. The gases then pass through an iron-based catalyst to create ammonia gas, which is cooled to become liquid anhydrous ammonia. The ammonia is then pumped into nearby storage tanks, and residual hydrogen and nitrogen are recycled through the system. The process uses 10 percent of one turbine's energy capacity.

Economies of scale

The idea is that a plant like this could produce enough fertilizer for a group of farms or a small-town cooperative, Reese says. Annually, the center will produce about 25 tons of fertilizer and sell it to farmers via Morris area co-ops. That's a tiny portion of what local farmers need, but it provides an alternative that may grow over time as the facility proves itself.

Scientist Joel Tallaksen is using life-cycle analysis models to evaluate exactly how much fossil fuel can be saved by using the system, as well as the costs of energy inputs and the net carbon balance. Though Tallaksen is still gathering and quantifying that data, he says it's clear that the process will save "a lot of fossil fuel energy."

Consumer demand

Economics then, are surely part of the puzzle, Reese says, but consumers' opinions will play a role in whether the process catches on. He believes that consumer demand eventually will lead toward greener fertilizers.

Indeed, a growing "field to market" movement within agriculture and the food sector, especially among large corporations, is working toward sustainability throughout the food chain. Reese and the center recently had a visit from members of the World Wildlife Fund, which is working with companies like General Mills and Coca-Cola that are responding to consumer demand for sustainable products.

"Consumers are looking for food products that have a low-carbon footprint, and these companies are taking notice of that," says Reese.

Coca-Cola, as one might guess, uses a lot of corn syrup in the manufacturing of soda. So if consumers are pushing for a lower carbon footprint, says Reese, one of the best options for Coke is to use corn syrup and grain made with renewable energy fertilizer.

"Fertilizer accounts for roughly 14 percent of the carbon footprint of corn production," says Reese. "So if we can produce fertilizer in a renewable way, we can take out a big portion of that."

A version of this story originally appeared in the spring edition of Solutions magazine, a publication of the College of Food, Agricultural and Natural Resource Sciences.

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