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Pros and cons of cellulosic ethanol

Sunday, October 30, 2011

Several weeks ago, I wrote an update on cellulosic ethanol. This is a bio-fuel produced from wood, grasses, or the non-edible parts of plants. While the use of bio-fuels has been controversial, their use is mandated by Congress by the The Energy Policy Act of 2005.

The use of bio-fuels is to lessen the dependence of the United States on Organization of Petroleum Exporting Countries (OPEC). While this is an admirable goal, bio-fuels are also replacing domestic oil and gas production.

Production of ethanol from cellulosic crops and agricultural waste has the advantage of abundant and diverse raw material compared to sources like corn and cane sugars, but requires a greater amount of processing to make the sugars available to the microorganisms that are typically used to produce ethanol by fermentation. So the plant designs for corn bio-fuel will not work for cellulosic ethanol.

Switchgrass and Miscanthus are the major biomass materials being studied today, due to their high productivity per acre. However, any source of cellulose would work. Dr. Gene Steven at the University of Missouri has conducted research on the use of sweet sorghum as a bio-fuel crop and concluded that it uses fewer inputs such as fertilizer than corn.

While the food vs. food debate continues to put crop-based bio-fuel production on the back burners it might just be industrial hemp that blazes the competition. Researchers at University of Connecticut have found that industrial hemp has properties that make it viable and even attractive as a raw material, or feedstock, for producing biodiesel. Hemp biodiesel has shown a high efficiency of conversion (97 percent) and has passed laboratory?s tests, even showing properties that suggest it could be used at lower temperatures than any biodiesel currently on the market.

However, for industrial hemp to be grown in the U. S., it must be licensed. Vermont and North Dakota have passed laws enabling hemp to be licensed. Both states are waiting for permission to grow hemp from the DEA. Currently, North Dakota representatives are pursuing legal measures to force DEA approval. Oregon has licensed industrial hemp as of August 2009[update]. The problem with industrial hemp is that it is the same plant as marijuana except that it has low tetrahydrocannabinol (THC) content. So law enforcement agencies are not keen to having commercial production of a plant that they cannot tell apart from marijuana.

Another plant that produces a large amount of bio-mass is palmer pigweed, Amaranthus palmeri. At the Delta Center Field Day, Dr. Reid Smeda, a weed scientist at MU mentioned that its seed protein has good quality. It also produces a lot of bio-mass. It is unlikely that it would be used for bio-fuel production.

North Carolina is working on cellulosic ethanol production and they are allowing the use of a Giant Reed, Arundo donax, to be used in research plots. One of the problems with this plant is that it is extremely invasive. So North Carolina officials are restricting its production to only two counties far away from the traditional row crop production.

According to U.S. Department of Energy studies conducted by Argonne National Laboratory of the University of Chicago, one of the benefits of cellulosic ethanol is that it reduces greenhouse gas emissions (GHG) by 85% over reformulated gasoline.

Bio-mass crops also offer potential income to producers and they could receive carbon credits for growing these crops. Since the biomass crops have higher yields, less land would be needed for ethanol.

There are also soil and water quality benefits. The biomass crop would leave the land protected and the roots would add to the soil structure. The soil health effects would increase water infiltration and reduce runoff.

There are also drawbacks to cellulosic bio-fuel production. It takes greater processing to produce ethanol. The bio-mass crops have less energy than corn grain and would require much more volume. Getting this biomass to a production facility would require greater transportation costs. It is unknown what impact that the biomass crops would have on wildlife habitat.

There is an estimate of how much producers would make with biomass crops. However, once these cellulosic plants come on line, it is likely that the fuel plants will offer less money that the producer will need for him to grow the crop.

Regardless of method used for bio-fuels, a lot of water is needed for processing. It takes about four gallons of water to process each gallon of ethanol. One of the largest problems with cellulosic ethanol production is the economics of constructing the plants and getting investors.

The American company Range Fuels announced in July 2007 that it was awarded a construction permit from the state of Georgia to build the first commercial-scale 100-million-US-gallon per-year cellulosic ethanol plant in the United States. Construction began in November, 2007. The Range Fuels plant was built in Soperton, GA, but was shut down in January 2011 without ever having produced any ethanol commercially. It had received a $76 million grant from the US Dept of Energy, plus $6 million from the State of Georgia, plus an $80 million loan guaranteed by the U.S. Biorefinery Assistance Program.

Green energy often comes with a high price and is often not sustainable over the long run.

University of Missouri Extension programs are open to all

Dr. Michael R. Milam is an agronomy specialist and county program director with University of Missouri Extension in Dunklin County.

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