Biofuel’s New Baby: Switchgrass

200810711.jpg

Credit: Image courtesy of USDA-ARS

I’ve always been skeptical about biofuel technology, mainly because its illogical to think that land and crops currently being used as food sources should be converted to ethanol production. More recent developments and findings with cellulosic crop-based fuels, however, have caught my eye.

Switchgrass has been getting more buzz recently, especially since the feasibility of corn ethanol has been called into question (negative net energy). Here’s some fun facts on the potential of switchgrass:

  • Recent study showed 5 times the energy output (ethanol) to the energy input (energy needed to grow, harvest, and process the switchgrass into ethanol).
  • Essentially carbon neutral — absorbs as much carbon dioxide as it emits when the ethanol is burned.
  • Can be grown on farmland no longer fit for crops.

What do you guys think? Does ethanol from switchgrass stand a chance versus fuel cells, liquid coal, or electric vehicles?

jk

http://sciencenow.sciencemag.org/cgi/content/full/2008/107/1?rss=1

http://bioenergy.ornl.gov/papers/misc/switgrs.html

http://www.scitizen.com/screens/blogPage/viewBlog/sw_viewBlog.php?idTheme=14&idContribution=1377

    Thanks to David Fridley for the following:

    “The original article published in the Proceedings of the National Academy of Science (PNAS) was revealing, since there they have the underlying data tables. The “5 times” return is an accounting fiction: they omit completely the bioenergy used as fuel input in the ethanol plant, and credit the ethanol produced with over 5 MJ/liter of electricity sold (these are results of a model only, since no such plants actually exist). Biomass is energy, and omitting it is like saying a biomass power plant consumes no energy because it burns wood.

    Cellulosic ethanol is far from carbon neutral. That could only be achieved if the feedstock could plant itself, harvest itself, transport itself, process itself, and transport itself again to your fuel tank. Otherwise, all those stages of the process will require fossil fuels.

    The Achilles heel of all ethanol is both the water requirement (higher for cellulosic than starch or sugar) and the requirement of distillation and dehydration. These two steps alone consume 1/3rd of the energy in the final product, not counting anything other energy use in the chain. The high “returns” you read about from Brazilian sugarcane or in this article results from omitting the biomass energy input to the process. Thermodynamically, ethanol simply can never provide much of a net energy return.”

    Here’s a link to the original paper published by the PNAS.  (Login or university connection required)

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    9 Responses

    1. Scientific american also has a story on it:

      http://www.sciam.com/article.cfm?id=grass-makes-better-ethanol-than-corn&

      Its an interesting possiblity, though none of these articles are clear on how far this kind of stuff is from being ready for the market. Is more technology needed, or just infrastructure? I’d also be interested to see roughly how much dedicated land it would take to fuel the needs of the average car. An acre? A hundred?

    2. 4,896 barrels of bioethanol per square mile. I beleive there are 42 gallons in a barrel of crude oil…. not sure if the same units apply to barrels of bioethanol.

    3. Hmm, so assuming for the sake of argument that bioethanol is just as efficient as gasoline, that means that a square mile can produce enough fuel so that a 30 mpg car can go 6854 miles. Assuming that was a yearly yield figure, and a rough guess that the average car travels 15000 miles per year, that means it’d take 2.2 square miles to satisfy the needs of that car. Seems pretty infeasible…

    4. The original article published in the Proceedings of the National Academy of Science (PNAS) was revealing, since there they have the underlying data tables. The “5 times” return is an accounting fiction: they omit completely the bioenergy used as fuel input in the ethanol plant, and credit the ethanol produced with over 5 MJ/liter of electricity sold (these are results of a model only, since no such plants actually exist). Biomass is energy, and omitting it is like saying a biomass power plant consumes no energy because it burns wood.

      Cellulosic ethanol is far from carbon neutral. That could only be achieved if the feedstock could plant itself, harvest itself, transport itself, process itself, and transport itself again to your fuel tank. Otherwise, all those stages of the process will require fossil fuels.

      The Achilles heel of all ethanol is both the water requirement (higher for cellulosic than starch or sugar) and the requirement of distillation and dehydration. These two steps alone consume 1/3rd of the energy in the final product, not counting anything other energy use in the chain. The high “returns” you read about from Brazilian sugarcane or in this article results from omitting the biomass energy input to the process. Thermodynamically, ethanol simply can never provide much of a net energy return.

    5. One other source which considers the controversial ideas related to using biofuels. Professor Crutzen, who won the Noble Prize 2007 has shown:

      http://www.atmos-chem-phys-discuss.net/7/11191/2007/acpd-7-11191-2007.pdf

    6. To elaborate more: First of all, Biofules are considered to be carbon neutral but in practice, they are NOT. This is because energy is used to grow crops (fertilizer manufacturing, used machinary), process them into fuels and transport them. Besides, The 2007 study by Professor Crutzen et al. (link above) shows that the advantages of reduced carbon dioxide emissions are more than offset by increased nitrous oxide emissions. In addition, Biofuel advantages are also critiqued in terms of their unfavourable effects on land use changes and soil carbon losses. In other words, large scale biofuel production should be considered when the land has been a desert or paved area.

    7. Terrific information. Hope to come back again..

    8. I think you guys are putting way too much into this…there is no free fuel. So what are we to do stay on oil? Stay on coal? No! This is the next step if we do not start now,when? So instead of worrying about 100% neutral we can start by replacing 50% of the coal in our power plants with a type of pellets that can be regrown instead of blowing up a mountain to get the coal.

      Your thoughts…

    9. Quality Information Thanks!

      I have bookmarked your site, if you get a chance please take a look at our site

      http://www.bio-partners.co.uk

      there is some more information you may find useful in our members area!

      Warm Regards,

      Dougie

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