{"id":2935,"date":"2008-05-08T09:24:33","date_gmt":"2008-05-08T15:24:33","guid":{"rendered":"http:\/\/wordpress-367309-1145705.cloudwaysapps.com\/2008\/05\/08\/part-2-there-are-good-and-bad-biofuels\/"},"modified":"2008-05-08T09:24:33","modified_gmt":"2008-05-08T15:24:33","slug":"part-2-there-are-good-and-bad-biofuels","status":"publish","type":"post","link":"https:\/\/sustainablog.org\/articles\/part-2-there-are-good-and-bad-biofuels\/","title":{"rendered":"Part 2: There Are Good and Bad Biofuels"},"content":{"rendered":"

\"cornstalks\"Today’s post is by Dr. Bill Chameides<\/a>, dean of the Nicholas School of the Environment<\/a> and lead author of the forthcoming blog The Green Grok. This is the second post in a 2-part series on biofuels.<\/em><\/p>\n

Last week’s topic<\/a> was why corn ethanol is an environmental loser.<\/p>\n

But are all biofuels losers? No. Some can be winners. One of those is called cellulosic ethanol.<\/p>\n

What Is Cellulosic Ethanol?<\/h3>\n

All ethanol \u2014 whether it is corn or cellulosic \u2014 is the same chemical compound: C2H5OH. You might recall from elementary chemistry courses that the “OH” group at the end of the formula indicates that the compound is an “alcohol.” Alcohols can have varying numbers of carbon atoms. Alcohol with two carbon atoms is called “ethanol.” The other alcohols are generally too toxic to be ingested, and thus ethanol has been the libation of choice down through the ages. (Ethanol used as fuel is rendered nonpotable.)<\/p>\n

So corn ethanol and cellulosic ethanol don\u2019t signify different types of ethanol, but rather the different material (or feedstocks) used to produce them.
\n<\/p>\n

Why Cellulosic Ethanol Can Be an Environmental Winner<\/h3>\n

Corn ethanol is produced from kernels \u2014 actually only a small part of the corn kernels \u2014 the sugars and starches. Herein lies one of the limitations of corn ethanol. You see, sugars and starches comprise a tiny fraction of the corn plant\u2019s mass \u2014 about 2-15%. Because only a small fraction of a plant is used to make corn ethanol, the amount you can produce is limited.<\/p>\n

Cellulosic ethanol is a different story. Most of the dry biomass \u2014 as much as 80% \u2014 is typically made up of cellulosic material \u2014 the stuff that makes the plant sturdy. So you can make a lot of ethanol using a plant’s cellulose instead of its sugars and starches. (By the way, even if the cellulosic material comes from corn, we still call it “cellulosic ethanol.” Corn ethanol is made solely from the sugars and starches of the corn kernel.)<\/p>\n

The Major Advantage of Cellulosic Ethanol<\/h3>\n

Our guts are unable to digest cellulose, so we typically throw away that part of crops. A lot of it is left on the field or disposed of as agricultural waste. For corn, the cellulosic material includes the corn stover \u2014 the leaves and stalk \u2014 and the cob.<\/p>\n

Remember what made corn ethanol such an environmental negative? A main reason is that it requires that land being used to grow food (or left as forests or grassland) be converted to growing an energy crop. And that leads to lots of global warming pollution.<\/p>\n

This is not a problem for cellulosic ethanol \u2014 we can simply use the agricultural waste from food crops to make the ethanol and thereby avoid all those emissions.<\/p>\n

Why We Can\u2019t Fill Our Tanks With the Cellulosic Stuff … Yet<\/h3>\n

Unfortunately, right now, producing cellulosic ethanol on an industrial scale is too expensive. Unlike converting a plant’s sugars and starches to corn ethanol, making cellulosic ethanol requires that we first break down the cellulosic material. But because this material is what makes a plant sturdy, the atoms in these compounds are strongly bonded together and that makes them hard to break apart. The processes we have available today to do this are too expensive to make cellulosic ethanol commercially competitive.<\/p>\n

But that will likely change. Scientists and engineers are working to make a commercially viable form of cellulosic ethanol. Some are developing new chemical processes; others are trying to genetically engineer new microbes that can “ferment” cellulose into ethanol like normal microbes that ferment sugars into ethanol. (The U.S.Department of Energy is helping fund six biorefineries<\/a>.)<\/p>\n

Cellulosic Ethanol Could Help Cut U.S. Global Warming Pollution<\/h3>\n

By my own estimates, agricultural and forest wastes could supply as much as 35 billion gallons of ethanol per year, saving up to 76 megatons of global warming emissions per year. (These results are somewhat larger than but consistent with other recent estimates (e.g., see Smith et al. 2004).) Such savings would cut a little less than 5% of all our heat-trapping pollution and about 15% of the emissions from the transportation sector.<\/p>\n

By mid-century, cellulosic ethanol could supply as much as 86 billion gallons of ethanol, saving a little more than 180 megatons of global warming pollution per year \u2014 or almost 12% of America\u2019s total global warming pollution and about 35% of the emissions from the transportation sector.<\/p>\n

These are significant numbers. But to reach such levels we would need to grow bioenergy crops such as switch grass. Such cultivation, in turn, would require converting lands for this purpose, and that could raise some of the problems discussed in last week’s post<\/a>.<\/p>\n

The Bottom Line of Biofuels: There Are Winners and Losers<\/h3>\n

The saying “waste not, want not” applies to biofuels. The best biofuels are made from agricultural or forests wastes or from plants cultivated on degraded or marginal lands. The product from such feedstocks \u2014 cellulosic ethanol \u2014 is where we should be directing our entrepreneurial energies.<\/p>\n

\"Dr.Read more about Dr. Bill Chameides<\/a>, Dean of the Nicholas School of the Environment and Earth Sciences at Duke University.<\/p>\n

See also:<\/strong><\/p>\n

CleanTechnica: Gene from Cow’s Stomach Engineered to Create More Affordable Biofuel<\/a><\/p>\n

Gas 2.0: Mascoma Update — Cellulosic Ethanol Company Adds $10 Million From Marathon Oil<\/a><\/p>\n

CleanTechnica: First Sustainable Ethanol to Mass Market?<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

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