December 15, 2011
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.”
Small-scale anhydrous plants
Small-scale anhydrous plants could also offer farmers a chance to own or invest in the production capacity for one of their primary crop inputs, says Riley Maanum, research director for the Minnesota Corn Growers Association, which helped fund the wind-to-ammonia project.
An efficient infrastructure for handling and distributing ammonia – from pipelines to storage and load-out facilities to the regulatory framework – already exists. And because electricity prices are less erratic than natural-gas prices, Maanum adds, electrochemical ammonia production could offer a more stable and predictable N fertilizer price for farmers.
The biggest hurdlewill be cost.“If we can achieve the methods to produce ammonia from wind at a cost that’s competitive, it would be fantastic for Midwest farmers,” says Roger Imdieke, who raises corn, soybeans and dairy heifers in central Minnesota. Although renewables are appealing to farmers, “When it comes down to it, they will make their decisions based on the bottom line.”
Gross margins for ammonia production from natural gas have risen sharply in the past decade, due to strong fertilizer demand, says University of Minnesota Extension Economist Doug Tiffany.
However, electrochemical ammonia manufacturing has high capital costs, WCROC’s Reese says, a disadvantage for small-scale plants. It takes more energy, too – roughly one-third more than making fertilizer in a new, efficient natural-gas steam methane reform plant.
Still, tapping the excess electricity now produced by Midwest wind farms could lower production costs enough to make electrochemical processing competitive, says Tiffany, an expert on renewable-energy economics.
You’ve probably seen idle wind turbines that aren’t turning on windy days, and wondered why. It’s because “at that time, there’s no demand for the electricity,” so power production must be curtailed, Tiffany says. “This is cheap power – if we could find something useful to do with it. Ammonia might be it.”
And if natural-gas prices balloon, or the nation decides to tax greenhouse-gas emissions, wind power becomes “a clear price leader,” Reese adds.
It may be feasible to harness other local renewable power sources, too, says Norm Olson, alternative fuels program manager at the Iowa Energy Center, which is investigating the production of ammonia from biomass. Just half a ton of gasified corn stover produces an acre’s worth of anhydrous ammonia, he says. “Farmers know the value of corn stalks, so they could fix their ammonia costs from now until they retire.”
Anaerobic digestion of manure and ag residues, which is becoming more common in large dairy operations, is another alternative power source, Olson says. “Ammonia is one of the highest-value materials you can produce from anaerobic digestion.”
Locally made ammonia could have important advantages over imported fertilizer.
It wouldn’t need to be shipped very far, says Brian Kruize, manager of the Morris Co-op Association, a large farm-supply and agronomy cooperative. “Anhydrous comes to west-central Minnesota by rail,” Kruize notes. “And if the railroad decides not to handle anhydrous anymore, as they’ve been talking about for 10 years, we won’t be able to get it.”
Beyond that, says economist Tiffany, renewable N fertilizer would slash corn’s carbon footprint by more than half. “I believe all of agriculture will be measured on this standard in the future,” he says. “Whether meat, milk, eggs or ethanol are made from corn, the carbon footprint of the products will be reduced. That could be a real competitive advantage in future years.”
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