Answer to fertilizer woes blowing in the wind, says researcher


Here’s an interesting experiment: On a hot day, open a six-pack of beer with your buddies and start drinking.

When there’s only two left, observe the dynamics. The degree of thirst and the attitudes of the company present will determine how the situation gets resolved.

That in a nutshell, describes the current global fossil fuel predicament, according to Michael Reese, renewable energy director at the University of Minnesota.

“We’ve reached peak oil. Twothirds of the world’s easy oil has been used up. We’re going to see ever-increasing costs for fossil fuels. If it was a six-pack of cans, and there’s four empty ones, that’s a serious problem,” he joked.

To promote research into alternative energy sources, the institution has set an ambitious target of becoming carbon neutral by 2010 using wind power and other sources.

The U. S. uses 25 per cent of the world’s oil production, and competition for liquid fuels from developing countries such as India and China in the coming years will intensify as their two billion citizens adopt western-style lifestyles, including cars.

New energy solutions

The United States, a major oil exporter up until 1970, now imports almost 70 per cent of its petroleum; the cost is crippling its economy. That reality, and growing evidence that global warming is a genuine threat, is driving the university’s desire to move beyond lab experiments and develop real-world renewable energy solutions that make business sense.

With a 1.6-megawatt wind turbine currently supplying about 60 per cent of the campus’s energy needs, some of the power is used for experiments aimed at either storing excess electricity or adding value in ways that would benefit the local economy.

Since Minnesota is farm country, using wind-generated electricity to make ammonia fertilizer makes a lot of sense, said Reese, noting making anhydrous ammonia from renewable energy sources is not new technology.

In the 1920s, Norway’s hydroelectric utility developed a similar process as a way to make use of 150 megawatts (MW) of power generated by a remote island generating station. Bulk anhydrous tanks were filled on site, then shipped by rail and barge to consumers elsewhere. The plant was closed, however, after much cheaper processes using natural gas were developed.

Fertilizer demand

Reese noted that over half of the nitrogen fertilizer used by American farmers is imported, and demand for nitrogen-based fertilizers is strong in Minnesota, which has heavily promoted corn-based ethanol as a means of stimulating the local economy and reducing dependence on foreign oil.

But since corn needs nitrogen almost as much as it needs water, developing NH3 from a renewable source “protects the flank” of corn-based ethanol, he said, and the existing NH3 distribution infrastructure can easily handle local production via nurse tanks. The gas can also be further processed into other products such as urea.

“One thing about anhydrous is that it is much easier to store and transport than hydrogen,” he said, adding that anhydrous ammonia is the second-most transported chemical in U. S.

Hydrogen is touted as the fuel of the future, but it is a very low-density gas, and must be pressurized at 10,000 PSI in order to transport it in meaningful quantities. Converting it to NH3, on the other hand, makes it more “compact” because of the nature of the molecule.

Using current technology, running cars on corn-based ethanol fertilized with wind-generated NH3 would cost about $5.50 per gallon, but within 20 years, the cost could be driven down to around $2.70 per gallon, he said.

Wind power

Minnesota, which produces about a billion bushels of corn per year, uses the equivalent of 1.2 billion pounds of anhydrous ammonia to grow the crop. That demand could be met with two gigawatts of wind-generated electricity.

A thousand two-MW turbines – which could be built for less than the cost of a transmission line from the Dakotas to Chicago – could be used to supply the state’s entire N fertilizer demand and also make productive use of power generated during off-peak hours.

The model the university is developing uses a modified Haber-Bosch system to combine nitrogen from the air and hydrogen separated from water via electrolysis in a reactor the size of a 50-gallon drum. It can produce about a quarter-ton of NH3 per day at 20 per cent efficiency. Construction is set to begin in spring, with the system reaching full production by the fall of 2009.

“This is a system that can be used at a relatively small scale,” he said, adding that further research will be aimed at commercializing it, and improving efficiency.


In comparison, a typical 50-MW plant capable of producing 36,000 tons of NH3 per year uses $2,500 worth of electricity per hour, at a rate of five cents per kilowatt.

Jump-starting renewable anhydrous ammonia production could be as simple as legislating a five to 20 per cent renewable NH3 mandate, providing production incentives or offering blending credits for existing producers, he said.

At 6.5 cents per kilowatt, NH3 made using electricity instead of natural gas would cost about $540 per ton.

“I think it would cost farmers about $5 per acre extra in the short term. In the long term, I believe it is going to be cheaper to use electrical energy than natural gas in 10 to 20 years,” he said.

“Farmers own the land that the wind blows across, and they also own the nitrogen fertilizer demand. So, you could potentially have vertically integrated, locally owned systems that would allow for moderately priced fertilizer over the long term.” [email protected]

About the author



Stories from our other publications