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Fluid Journal : Fluid Journal 2005-2007
10 Fluid Journal FALL 2007 A likely scenario is depicted in Table 1 where per acre use in the new corn area is assumed to be the same as that reported by the USDA Survey. In other words, the new corn acres are fertilized as in the past. It is also assumed that the 10 million acres are drawn from soybean ground so that the fertilizer that would have been applied on soybeans is subtracted from the new total applied on the corn. However, continuous corn does not receive a soybean credit so N use will likely increase on those acres by perhaps 30 lbs/A. Since there will be 10 million fewer acres of soybeans to rotate with corn in the second year, an increase of 10 million acres of corn this year results in 20 million acres of corn on corn the following year. With these adjustments made, a 10 million acre increase in corn would result in U.S. increases of 7.6, 3.5, and 2.6 percent in N, P, and K use, respectively. An additional 3 million acres of corn appears to have been taken out of cotton acres in 2007. Since fertilizer use on corn and cotton is more similar than between corn and soybeans, the impact of this shift in cropping on fertilizer use is expected to be considerably less. Biomass The production of ethanol from cellulosic biomass occurs today only on a pilot basis but progress is being made toward commercialization. Iogen Corporation has been operating an 800,000 gallon/year demonstration scale facility in Ottawa, Canada, producing ethanol from wheat straw. This facility represents the final proving stage prior to full-scale commercial bio-refineries, each designed to process annually more than 1.5 million dry tons of crop residues into 100 million gallons of ethanol. In 2007, Iogen also plans to initiate construction of a 20-million gallon commercial plant in Idaho's Snake River Valley to make ethanol from wheat straw, with operation anticipated by 2009. Abengoa Energy, and DuPont and Broin have announced plans to get into cellulosic ethanol production. If cellulosic ethanol production does become a commercial reality as many experts are predicting, the impact on the fertilizer industry and nutrient cycling could be large, especially for K. Corn stover is expected to be a major initial feedstock due in part to a plentiful supply, with current sustainable availability estimated at 75 million tons per year (Figure 2). Nutrient content of stover entering a bio- refinery could be extremely variable due to variation in plant nutrient uptake, foliar leaching during crop senescence, extent of weathering in the field, or harvest techniques. Using average figures, 75 million tons of harvestable corn stover would contain nutrients equivalent to 6, 5, and 23 percent of annual fertilizer sales of N, P, and K, respectively. Thinking in terms of bio- refinery capacity helps visualize how a commercial cellulosic industry might get started. Though bio-energy literature indicates considerable uncertainty in commercial scale details, an 80- million gallon refinery seems to be in the central range of the capacities presented as does an estimate of 80 gallons of ethanol per dry ton of stover. Therefore, a reasonable estimate of the stover demand for a refinery is a million tons of stover Table 1. Impact of adding 10 million acres of corn from soybean acreage in the U.S. Fertilizer use (1,000 tons) Change N P2O5 K2O + 10 million acres of corn 660 234 270 - 10 million acres of soybeans -26 -76 -136 Net +634 +158 +134 Based on USDA Ag Chemical Use Survey, average of 2003 and 2005 for corn and 2002 and 2004 for soybeans. Perlack et al., 2005 Other Crop residues 21 Other Small Grains 6 Corn Fiber 6 Wheat Straw 11 Corn Stover 75 Million Dry Tons Per Year Figure 2. Current sustainable availability of cellulosic biomass from agricultural lands.
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