Using the Wind to Fertilize Corn
AgMRC Renewable Energy Newsletter
value-added agriculture specialist
Iowa State University Extension
(first in a series)
What does the upper Midwest and Great Plains need a lot of – nitrogen fertilizer. Nitrogen fertilizer is used to grow the mountains of grain for the U.S. and the world. What does this area have a lot of – wind. Wind comes down from the Canadian prairies and blows across the plains. Wouldn’t it be nice if we could magically make nitrogen fertilizer out of wind? It may not be that far-fetched.
Nitrogen fertilizer is a major component of the cost of producing corn. Iowa State University crop budgets for 2009 show a nitrogen fertilizer cost of $75 per acre of corn following soybeans and $105 per acre of corn following corn. Iowa and Minnesota farmers combined planted 20 million acres of corn in 2008. A continuation of this acreage in 2009 would cost Minnesota and Iowa farmers about $1.6 billion dollars. Nitrogen fertilizer costs for all U.S. corn farmers could be close to four times this amount.
Figure 1. Anhydrous ammonia is being applied to a field of corn.
Nitrogen fertilizer is made from ammonia (NH3). The most elemental nitrogen fertilizer is anhydrous ammonia (ammonia without water). But ammonia can be oxidized to make nitrates (NO3) and nitrites (NO2) for other nitrogen fertilizers. So, nitrogen fertilizers like urea and UAN (urea and ammonium nitrate in water) are also ammonia based.
The technology for making ammonia is not new. Fritz Haber, a German chemist, first demonstrated the production of ammonia using atmospheric nitrogen in 1909. The process was purchased by the German company BASF. Carl Bosch successfully scaled up the process for industrial production in 1913. Both Haber and Bosch were awarded a Nobel Prize for their work.
The Haber-Bosch process combines nitrogen and hydrogen to produce ammonia. Nitrogen is taken from the atmosphere. The air we breathe is 78 percent nitrogen. However, it is relative un-reactive as the molecules are held together by a strong triple bond.
Originally the source of hydrogen was water (H2O). Essentially the water molecule is split into its components of hydrogen and oxygen through a process of electrolysis. Electrolysis is the process of passing an electric current through water to decompose water (H2O) into oxygen (O2) and hydrogen (H2). Two electrodes are placed in water. Hydrogen will appear at the cathode (negatively charged electrode) and oxygen will appear at the anode (positively charge electrode). The electrolysis of pure water is very slow. To speed up the process an electrolyte (e.g. salt, etc.) is added. The first electrolysis dates back to about 1800.
In World War I, ammonia was used for the production of gunpowder and high explosives. During World War II, ammonia production from methane (CH4) was substituted for ammonia from the electrolysis of water. Methane (natural gas) has since been the primary source of hydrogen rather than water. Coal is increasingly being used in China to produce low-cost ammonia.
The Haber-Bosch process requires high pressures and very high temperatures. Research is underway to find a way to convert nitrogen to ammonia at ambient pressures and temperatures. There are several companies that offer proprietary designs for ammonia production.
Changes in U.S. Ammonia Production
After many years of expansion, the U.S. ammonia industry has gone through difficult times. U.S. ammonia production capacity increased gradually until 2000 when it started to decline. Up until 1998, production capacity was fully utilized. After 1998, production started to drop and production capacity was idled. From 2000 to 2006, ammonia production declined from 18 million tons to 10 million tons, a 44 percent decline. During the same period, the number of ammonia plants declined from 40 to 25 and production capacity declined from 20 million tons to 13 million tons.
The deficit in U.S. produced nitrogen fertilizers during this period was filled with imported fertilizer. As shown in Figure 2, the percentage of the nitrogen fertilizer that we import has increased substantially during recent years. A decade ago we imported 35 percent of our usage. In 2007 we reached a high of almost 80 percent.
(Click to enlarge.)
The Trinidad and Tobago Republic (a group of islands in the southern Caribbean) is the largest exporter to the U.S. Canada, Russia and Ukraine are also major suppliers. The imports of each of the three major types of nitrogen fertilizer (anhydrous ammonia, urea and nitrogen solutions) have increased over the last ten years.
Because the major cost of producing ammonia is closely associated with the price of natural gas, the price of ammonia is very volatile and tends to follow the natural gas price. When energy prices skyrocket, the price of ammonia also soars, making it very difficult for farmers to budget returns for their farms.
Wind to Ammonia
Due to the concerns of using a fossil fuel for ammonia production, scientists are once again examining the potential of using electrolysis as a production method. Finding an alternative source for hydrogen in the ammonia production process could greatly reduce our dependence on foreign sources of natural gas and ammonia. Also, if the hydrogen comes from a renewable source such as wind, the greenhouse gas emissions from producing ammonia are greatly reduced.
The Upper Midwest and Great Plains are an excellent source of wind power. As shown in Figure 3, the winds in this area are the strongest in the country except for the Rocky Mountain areas (the darker the blue, the stronger the wind). North and South Dakota, Western Minnesota and most of Iowa have strong average winds. Nebraska to the Texas Panhandle is also an area of strong winds.
Figure 3. U.S. Average Annual Wind Power
Source: Wind Energy Resource Atlas of the United States
Much of the wind power in these areas is characterized as “stranded” wind power. There is little need for the electricity locally and sufficient grids are not available to transport the electricity to population centers. However, developing uses for the wind power locally provides a use for stranded wind power. And the costly construction of an electrical infrastructure is not needed. Using wind power to produce nitrogen fertilizer to use in the fields around the wind towers is an example of the local use of stranded wind power.
Other Renewable Hydrogen Sources
Hydrogen sources other than wind electrolysis can also be used to make ammonia. The energy for electrolysis can come from an array of renewable energy sources such as solar, hydro and others. In addition, hydrogen can come from methods other than electrolysis. Many types of biomass can be used as hydrogen sources. For example, there is interest in using corn stalks as the hydrogen source. This would provide a “closed loop” for a farming community where the corn stover produced from the corn crop goes into making the nitrogen for the following year’s corn crop. Approximately one-half ton of corn stover would be sufficient to produce enough ammonia to fertilize one acre of corn. Of course stover removal may raise concerns about soil erosion, fertility (phosphorus and potash) removal and organic matter depletion.
Implication for Farmers
Below are some of the advantages to corn farmers from an alternative source of ammonia. For these processes to be viable, they must be cost competitive with the current method of ammonia production from natural gas. At high natural gas prices, these alternatives can be competitively priced. However, for their long term viability, they must also be competitively priced with low natural gas prices. Government programs that subsidize wind power and tax carbon emissions can improve the cost competitiveness of these alternatives.
- Secure Access to Fertilizer -- A domestic hydrogen source for producing ammonia can provide farmers with security of access to adequate supplies of nitrogen fertilizer.
- Less Price Volatility -- A domestic hydrogen source for producing ammonia can provide farmers with a more stable price for nitrogen fertilizer to assist them in financial planning.
- Improved Carbon Footprint -- A renewable hydrogen source for producing ammonia can reduce the carbon footprint of crop production.
- Economic Development -- A local hydrogen source for ammonia production can provide an economic development opportunity for farmers and rural communities.
Implications for Ethanol
The impact of alternative ammonia production methods on corn production will also impact corn-ethanol production. Below are some of these impacts.
- Energy Self-sufficiency -- At a time when the U.S. is attempting to become self-sufficient in energy production, it is questionable whether relying on foreign sources of ammonia to produce the corn needed to produce ethanol leads us to self-sufficiency. Finding a domestic source for ammonia for corn production will help make ethanol a truly domestic energy source.
- Improved Net Energy Balance – Ethanol has been criticized for its narrow net energy balance. Producing ammonia from a non-fossil fuel source will improve the net energy balance for producing corn, which will subsequently improve ethanol’s net energy balance.
- Improved Carbon Footprint – At a time when we are concerned about the impact of carbon emissions on climate change, producing the corn for ethanol production from a renewable energy fertilizer source will improve the carbon footprint of ethanol. The 2007 energy legislation requires future corn-starch ethanol plants to reduce greenhouse gas emissions by 20 percent compared to gasoline. Nitrogen from renewable sources could help greatly in meeting this requirement.
The next article in this series will address the potential of ammonia as a transportation fuel.
Ammonia Fuel Network. 16 February 2009.
Huang, W. "Impact of Rising Natural Gas Prices on U.S. Ammonia Supply”. 2007. U.S. Dept. Agriculture, Economic Research Service. Report WRS-0702. 16 February 2009.
U.S. Fertilizer Imports/Exports. 2007. United States Department of Agriculture, Economic Research Service. 16 February 2009.
Anne Marie Helmenstine, PhD, What is the Chemical Composition of Air? 16 February 2009.