Monday, July 14, 2008

Corn Stover as a cellulosic ethanol source

Economist: Take 'stalk' in corn stover as state's ethanol future and Purdue Study Concludes Corn Stover Better Economically Than Switchgrass for Indiana Cellulosic Ethanol

"Cellulosic ethanol made from corn stover and switchgrass could be the next big thing in liquefied energy." At least in corn producing states like Indiana (the study was published by Purdue Univ). Generally ethanol derived from Corn has been seen as a bad idea because it is diverting food to make fuel. There are food riots around the world for a couple years now, due to higher prices for food, and these higher prices may be due (in part) to the diversion of corn (etc) into making fuel.

However Corn Stover is a byproduct of corn production which isn't the food portion of the corn plant. It is the other part, the stalks and leaves. This can be processed as cellulosic ethanol without diverting food for fuel.

Purdue conducted a study comparing Corn Stover with Switchgrass, and this Stover stuff came out better. However it looks to me their figures accounted only for monetary inputs, that by the money inputs to processing Stover it comes out monetarily better than processing Switchgrass. The article doesn't discuss whether it is better from the standpoint of energy inputs.

Gives some background on what Corn Stover is.

It says that in Europe (Netherlands and Belgium) Stover is used as animal feed during the winter. They harvest the entire plant and crush the part which isn't the corn husk.

The wikipedia article has this quote: “some agronomists question whether taking stover out of the field annually will have a negative impact on soil fertility and structure.” (link) I expect what they're getting at is if the Stover is left on the field then it will biodegrade on its own and become part of the future soil. But if it is removed then the soil isn't replenished by having the composted plant matter (Stover) feeding into the soil.

GMO Corn-Stover Eats Itself, Makes Ethanol Processing A Breeze and Researchers Modifying Corn With Genes to Produce Enzymes to Enable Simpler Production of Cellulosic Ethanol

"Researchers at Michigan State are trying to get corn-stover to digest itself after harvest. Doing so would mitigate the costly pretreatment steps needed for the production of cellulosic ethanol from the non-edible parts of the corn plant." -- This research would be an optimization of the processing of Stover.

The method is to genetically modify the corn -- so that it produces enzymes required to make the Stover break down more quickly. Uh.. lessee, they're adding a feature to Corn so that the byproduct can be reused more readily? This sounds like a way to distance food from being food, or rather they're putting effort into designing food with featureitis that isn't food-like. This reminds me of a conceptualized nightmare picture I saw long ago of "food engineering" gone awry; the idea was to make tomato's that packed more tomato per unit of space and therefore they genetically modified tomato's so they grew in a cube, because round tomato's have wasted space in the gaps due to round shape.

uh.. wait... Because it is only in the vacuole of the green tissues of plant cells, the enzyme is only produced in the leaves and stalks of the plant, not in the seeds, roots or the pollen. Meaning they've worked out how to genetically modify it so only the leaves and stalks are producing this enzyme. I feel much better.. maybe.

Measuring The Merits Of Corn Stover-Based Ethanol

This covers some of the same ground as before, but it goes into more details on the tradeoff with removing Stover versus leaving it in place. They say Stover left in place "may help prevent soil erosion caused by strong winds or intense rainfall. It also replaces lost nutrients and sequesters carbon in the soil, lessening CO2 accumulation in the atmosphere as a greenhouse gas and its contribution to global climate change." Hmm.. Stover left in place is a carbon sequestriation method? Really? And we want to interfere with this so we can make fuel?

Researchers Developing Machinery To Harvest Corn Stalks And Leaves

This discusses farm machinery being designed which makes it easier to harvest Stover at the same time corn is harvested. In the past it would take two combines to harvest the Stover and Corn, or else the Stover would simply be left in the field. This new machine is a simple addon to existing combines or I suppose could be built as a combined unit which does it all at once to harvest both corn and stover.

Nutrient removal when harvesting corn stover

This is excellent detailed examination of the chemical and nutrient makeup of stover. By removing stover from a field you are removing nutrients and carbon from the field, as discussed above.

It makes it clear that one effect of removing Stover would be the need for increased use of fertilizer. Fertilizer (in the U.S.) generally is made from oil.. soo.... removing Stover to make fuel causes an increase in oil consumption through increased fertilizer use???

Beef: Turn Corn Stover to Low Cost Pasture

A recommendation that Stover can be a good low cost cow feed. Hmm... sounds familiar..

Improving Biodegradability and Biogas Production of Corn Stover through Sodium Hydroxide Solid State Pretreatment

Chinese researchers in Beijing also researching methods to improve processing efficiency of Stover.

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