The Potential Role for Corn Ethanol in Meeting the Energy Needs of the United States in 2016-2030
Corn available for use in ethanol plants will continue to increase in volume after 2015 and could contribute significantly to the nation's renewable energy goals. Corn yields may increase to 289 bushels per acre by 2030 corn crop with total production of 24.6 billion bushels. With no increase in harvested corn acreage from the 2007 level of 85 million acres and growth in other uses of corn, corn available for use in ethanol production would be 12 billion bushels from the 2030 corn crop. This compares to 2.2 billion bushels used for ethanol from the 2006 crop.
If ethanol yield per bushel of corn remains at the current level of 2.75 gallons per bushel, total corn ethanol production in 2030 would be 33 billion gallons, compared to estimates of 7.1 billion gallons for calendar year 2007. If ethanol output per bushel of corn increases to 3.0 gallons per bushel, ethanol production would be 36 billion gallons.
Efficiency of use of commercial nitrogen fertilizer per bushel of corn produced will likely continue to improve from the current level of 0.9 pounds per bushel. The improved efficiency would reduce the amount of nitrous oxide (N2O), a greenhouse gas, released per bushel of corn produced. Continuation of the current trend of less use of anhydrous ammonia would also reduce the amount of N2O released in corn production. Commercial applications of phosphate and potash per bushel produced are also expected to decline, but not continue at the trend decline of the last 25 years.
A continued shift to more no-till corn production could reduce the amount of CO2 released in corn production because no-till corn is considered by some researchers as a carbon sink (more carbon is taken up by the soil than is released to the air in corn production). Some research indicates that minimum tillage programs can also reduce the amount of CO2 released.
The Agricultural Research Service (ARS) of USDA has begun a five year program, the Renewable Energy Assessment Project (REAP), to determine the amount of corn stover that can be removed without reducing long-term soil productivity. From a review of literature, the researchers estimate that more productive soils that are not highly erodible can be managed to allow some removal of stover.
About 20 percent of nation's corn production is irrigated and continued improvements in irrigation management and higher yields per acre should decrease the amount of water used per bushel of corn produced. Additional ethanol production per acre of corn produced could be achieved by using fiber from the corn kernel and some stover fiber to produce cellulosic ethanol. Poet, an ethanol plant builder and ethanol producer, is building an ethanol plant that is expected to produce 11 percent more ethanol from a bushel of corn by using the corn kernel fiber and 27 percent more ethanol from an acre of corn by using the corn kernel fiber and corn cobs for cellulosic ethanol production.
Improvements in the efficiencies of dry mill ethanol plants are expected to reduce the thermal energy used in the average dry mill ethanol plant on a per gallon produced basis in 2030 by 27 percent compared to 2007 and reduce electricity use by 46 percent.
A life cycle analysis of carbon intensity using the GREET model from Argonne National Laboratory using production estimates in this report shows the Global Warming Impact (GWI) from corn agriculture (on farm energy use for agricultural practices) could decline by 22% from 26,610 gCO2eq/MMBtu (grams of CO2 equivalent per million Btus) in 2010 to 20,755 gCO2eq/MMBtu by 2030. This is 25% below the current GREET default value of 27,469 gCO2eq/MMBtu.
The GWI of the average ethanol plant could decline from 63,959 gCO2eq/MMBtu in 2010 to 46,479 gCO2eq/MMBtu by 2030, a 27% decline. More significantly, the GWI of ethanol produced from the averaged ethanol plant in place in 2030 may be half the GWI of gasoline. The GWI of corn ethanol processed in a plant using a biomass combined heat and power (CHP) system in 2030 could be less than 1/3rd of the GWI of gasoline, 30,502 gCO2eq/MMBtu vs. 98,134 gCO2eq/MMBtu.
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