Tuesday, June 7, 2011
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Examples of sources for cellulosic ethanol include corn stover (the stalks and husks left over after harvest), wheat and barley straw, sugarcane or rice bagasse, sawdust, paper pulp, small diameter trees, dedicated energy crops such as switchgrass and other perennial grasses, and even municipal waste or household garbage.
How is cellulosic ethanol made? As with producing ethanol from grain, processing cellulosic sources extracts the fermentable sugars from the feedstock and distills them into alcohol. Unlike in grain, the sugars in cellulose are locked in complex carbohydrates called polysaccharides, or long chains of simple sugars. Separating these complex structures into fermentable sugars is essential to the efficient and economical production of cellulosic ethanol.
The ethanol produced from corn or milo and the ethanol produced from cellulose are chemically identical.
What is switchgrass? Why is it a good potential source for ethanol? Switchgrass, a perennial prairie grass, is one source likely to be tapped for ethanol production because of its potential for high fuel yields, hardiness, and ability to be grown in diverse areas. Switchgrass' long root system — actually a fifty-fifty split above ground and below — helps keep carbon in the ground, improving soil quality. It is drought-tolerant and doesn't require heavy fertilizing.
One of the advantages of switchgrass is that it can produce much more ethanol per acre than corn and it can be grown on marginal land that is not used to grow food crops. Also, it takes very little energy to grow the crop — significantly less energy than corn or soybeans.
How close is cellulosic ethanol to being commercialized? The technology to create cellulosic ethanol is available today and is in the early stages of commercialization.
This was adapted from Ethanol FAQ.