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?
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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