Clean energy from margins of agriculture?

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    Clean energy from margins of agriculture?

    Long-running efforts at efficiently converting woody plant materials to fuel got financial boosts this year from the U.S. Agriculture and Energy departments, as recently reported by Matthew L. Wald, writing in the NY Times. [ U.S. backs project to produce cellulosic ethanol from corn stover, July 7, 2011, at http://www.nytimes.com/2011/07/07/business/energy-environment/us-backs-plant-to-make-fuel-from-corn-waste.html ]

    For Mr. Wald, challenges of dealing with the lignins in plant materials are "technical hurdles." So far, those "hurdles" have defeated all efforts at commercial-scale production of cellulosic alcohols. No effective enzyme or other low-energy process has yet been found to dislodge hemicelluloses, and celluloses they usually enclose, from lignins that provide most of the strength of wood fibers, in yields adequate for commercial use. Only the hemicelluloses and celluloses can be converted into mixtures of sugars and fermented into alcohols for fuel.

    As long-time followers of the topics will know, it has proven difficult to obtain clean energy from the margins of agriculture: waste from food crops and plants growing on low-productivity land. Energy inputs are sometimes more than energy outputs, and overall greenhouse gas emissions are sometimes more than those from using oil or natural gas for energy.

    An advance so far unnoticed by Mr. Wald and little reported in general news media has been the demonstration that switchgrass--a widely occurring, native prairie grass--can be grown efficiently on marginal land, with long-term, large-scale cultivation yielding about a five-to-one return on energy inputs. [ M.R. Schmer, K.P. Vogel, R.B. Mitchell and R.K. Perrin, Net energy of cellulosic ethanol from switchgrass, Proceedings of the National Academy of Sciences 105(2):464-469, 2008, at http://www.pnas.org/content/105/2/464.full.pdf ]

    This year, switchgrass became an even more promising crop for biofuel production, with the announcement of a genetically engineered variant with low lignin. [ Chunxiang Fu, et al., Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from switchgrass, Proceedings of the National Academy of Sciences 108(9):3803-3808, 2011, at http://www.pnas.org/content/108/9/3803.full.pdf ]

    Low-lignin switchgrass is said to produce about one-third more fuel and require only about one-quarter as much of the expensive enzymes needed to produce cellulosic alcohols. While it might be possible that similar genetic engineering could improve the energy potential of corn stover, wheat straw, sugar cane bagasse and other wastes from food crops, genetic changes to those crops are much more susceptible to adverse side-effects than changes to crops not grown for food and not grown on prime agricultural land.

     
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    Re: Clean energy from margins of agriculture?

    In Response to Clean energy from margins of agriculture?:
    what about biofuel from algae, if not non-modified switchgrass/agricultural waste?
     

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