Wind + water + air = nitrogen (N) fertilizer.

It’s a formula that could bring farmers a local, renewable supply of ammonia, more stable N prices and vast new markets for Midwest wind power – markets that would not depend on building costly new transmission lines.

“It’s an elegant concept,” says Mike Reese, renewable energy director at the University of Minnesota’s West Central Research and Outreach Center (WCROC), Morris. “Farmers raise grains underneath wind turbines, which capture the energy to make fertilizer to feed the crop.”

This summer, the research center started making renewable anhydrous ammonia through wind-powered water electrolysis. Ammonia can be used directly as a fertilizer or processed into other forms of N fertilizer.

The $3.75-million pilot plant uses electricity from a nearby 1.65-megawatt (MW) wind turbine to separate hydrogen from water, and N from air. The gases are compressed and stored in banks of cylinders, then combined using a catalyst in a 25-gal. Haber-Bosch chemical reactor to form ammonia (NH3).

The Haber-Bosch process is proven commercial technology, although it hasn’t been used for small-scale processing, Reese says. The university research will look at the profitability of small ammonia reactors. New technologies will also be tested, including a low-temperature process that could be stopped and started more easily than the Haber-Bosch process, and efficient reactor catalysts that could quadruple ammonia yields.

The WCROC operation will produce 25 tons of anhydrous ammonia/year, consuming just 10% of the wind turbine’s electricity output. The fertilizer will be stored on-site and applied to the research station’s farm fields.

 

Turning wind power into fertilizer could benefit farmers in several ways, Reese says.

The Midwest has a wealth of under-used wind resources, which offer farmers a new source of revenue from their land – one that’s compatible with growing crops. But the Midwest and Great Plains utility industries don’t have enough transmission lines to transport additional electricity to big cities, where it’s needed. The result: An abundant renewable resource is “stranded” in rural areas where there’s little opportunity to sell it, Reese says. And the transmission problem is worsened by the intermittent nature of wind power.

At the same time, the windy Midwest and Plains states use lots of N fertilizer, some 4 million tons/year for corn alone. Meanwhile, ammonia manufacturing – the basis for all N fertilizers – has moved overseas to places where natural gas is cheap. (Natural gas accounts for about 90% of the cost of making N fertilizer.)

So, what to do with “stranded” wind power that’s generated in farmers’ fields, far from urban customers?

“Why not make fertilizer” for local customers, Reese asks.

In wind-rich rural areas, “We need to develop our own markets for wind power.” Rather than exclusively building transmission lines – costing more than $1 million/MW – in order to export Midwest electricity, “Why not develop an energy-intensive industry to use renewable energy close to where it’s produced?” The same market strategy could apply to traditional power sources, too, he adds. “It may be worthwhile to use both wind and grid-based power to keep production facilities operating at full capacity.”

This would create local markets for electricity, especially wind power, while supplying corn growers with “a renewable alternative to conventional N fertilizer.”