History
The first attempt at commercializing a process for ethanol from wood was done in Germany in 1898. It involved the use of dilute acid to hydrolyze the cellulose to glucose, and was able to produce 7.6 liters of ethanol per 100 kg of wood waste (18 US gal (68 L) per ton). The Germans soon developed an industrial process optimized for yields of around 50 US gallons (190 L) per ton of biomass. This process soon found its way to the US, culminating in two commercial plants operating in the southeast during WWI. These plants used what was called "the American Process" — a one-stage dilute sulfuric acid hydrolysis. Though the yields were half that of the original German process (25 US gallons (95 L) of ethanol per ton versus 50), the throughput of the American process was much higher. A drop in lumber production forced the plants to close shortly after the end of WWI. In the meantime, a small but steady amount of research on dilute acid hydrolysis continued at the USFS's Forest Products Laboratory. During World War II, the US again turned to cellulosic ethanol, this time for conversion to butadiene to produce synthetic rubber. The Vulcan Copper and Supply Company was contracted to construct and operate a plant to convert sawdust into ethanol. The plant was based on modifications to the original German Scholler process as developed by the Forest Products Laboratory. This plant achieved an ethanol yield of 50 US gal (190 L) per dry ton, but was still not profitable and was closed after the war.
With the rapid development of enzyme technologies in the last two decades, the acid hydrolysis process has gradually been replaced by enzymatic hydrolysis. Chemical pretreatment of the feedstock is required to prehydrolyze (separate) hemicellulose, so it can be more effectively converted into sugars. The dilute acid pretreatment is developed based on the early work on acid hydrolysis of wood at the USFS's Forest Products Laboratory. Recently, the Forest Products Laboratory together with the University of Wisconsin–Madison developed a sulfite pretreatment to overcome the recalcitrance of lignocellulose for robust enzymatic hydrolysis of wood cellulose.
US President George W. Bush, in his State of the Union address delivered January 31, 2006, proposed to expand the use of cellulosic ethanol. In his State of the Union Address on January 23, 2007, President Bush announced a proposed mandate for 35 billion US gallons (130,000,000 m3) of ethanol by 2017. It is widely recognized that the maximum production of ethanol from corn starch is 15 billion US gallons (57,000,000 m3) per year, implying a proposed mandate for production of some 20 billion US gallons (76,000,000 m3) per year of cellulosic ethanol by 2017. Bush's proposed plan includes $2 billion funding (from 2007-2017?) for cellulosic ethanol plants, with an additional $1.6 billion (from 2007-2017?) announced by the USDA on January 27, 2007.
In March 2007, the US government awarded $385 million in grants aimed at jump-starting ethanol production from nontraditional sources like wood chips, switchgrass and citrus peels. Half of the six projects chosen will use thermochemical methods and half will use cellulosic ethanol methods.
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 (380,000 m3)-per-year cellulosic ethanol plant in the US. 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. 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.
Read more about this topic: Cellulosic Ethanol
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