Ethanol Efficiency Redux

Renewable Energy Access has a recent article, "Setting the Record Straight on Ethanol" advocating the efficiency of ethanol.  The article is written by Nathen Glasgow and Lena Hansen of the Rocky Mountain Institute who point out that enzymes now permit ethanol to be made from any cellulosic feedstocks and the advantages of this technology- growth on marginal land, higher energy yield per acre, and less energy input by the farmers because the crops are  perennials.  They refer to U.S. Department of Energy data which indicates that for every one unit of energy available at the fuel pump, 1.23 units of fossil energy are used to produce gasoline, 0.74 of fossil energy are used to produce corn-based ethanol, and only 0.2 units of fossil energy are used to produce cellulosic ethanol.  The first commercial-scale enzymatic reduction hydrolysis plant is scheduled to be built and operational by Iogen within two years, producing ethanol at a targeted cost of $1.30 per gallon.  They also have to take a swipe at Dr. Pimentel for his most recent attempt at rebuking ethanol.

Its worth a read by anyone who hasn't made up their mind on the energy efficiency of ethanol.

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Comments

[JesseJenkins]

Excellent! It's about time someone computed some new numbers reflecting the advancements in ethanol production made in recent years. I'm so tired of hearing old debates using old numbers. Thanks for the heads up on this one...

[Gary Dikkers]

If the production of corn ethanol is so efficient, why do ethanol plants burn natural gas to mill and distill corn into ethanol?

I know two planned ethanol plants that have cancelled proposed sites because of problems getting natural gas. Why would they need natural gas if corn ethanol produces more energy than it uses?

Wouldn't a savvy ethanol plant operator who actually believed he or she was creating more energy than the plant was burning, simply divert a portion of the finished ethanol spewing forth from the "out pipe' and use that to run the plant instead of natural gas?

The answer is that corn ethanol does have a positive net energy balance, but most of that excess energy is locked up in a non-fuel form (dry distillers grains) that few except livestock farmers can make very good use of.

On a micro-scale DDG can be fed to cattle, but if corn ethanol was ever to go large scale in an attempt to replace gasoline completely, ethanol plants would be surrouned by piles and piles of DDG that few would want, could use, or could afford to haul away. The heaps of DDG piled around corn ethanol plants would look like the huge slag heaps around old coal mines.

Ethanol plants might have to burn the DDG as their source of thermal energy just to get rid of the stuff.

[HFT]

I think Gary has almost hit the nail on the head...and i do mean almost :-) It makes no sense for ethanol plants to burn natural gas for their energy needs because your not creating green energy. One pound of DDG from corn has a btu vaule of 9600. Current gasifacation technolgies can produce enough energy to provide 100% of an ethanol plants energy needs plus has left over DDG to sell as cattle feed....DDG sells for $90 a ton although this varies by season and can go to a low of $40. Keep your eyes open...with natural gas being at a all time high...these types of power plants are going to be up very soon.

[James Fraser]

Gary, I think you missed one of the main points of my post - Cellulosic ethanol is very energy efficient, requiring much less energy than current plants that burn large amounts of natural gas. One reason that current plants don't use part of their product for energy is that they are producing a liquid fuel which, until recently, has been more in demand than natural gas. Panda Energy has built 3, of a planned 5, ethanol plants using menthane produced in a dedicated waste digestor rather than using natural gas. They have determined that it is better to use the methane in ethanol production rather than producing electricity with it.

I believe BRI Energy is the name of the company using gasification that HFT was refering to.

Thermal processes, i.e. gasification/synthesis processes, that can use any carbonaceous feed stock, like the whole corn plant, grasses or fast growing trees, are under development. They eliminate the distillation and produce an excess of electricity. One is being built in Europe by Choren but they are very capital intensive and would have to be built on a larger scale than any current ethanol plant to be economical.

DOE has an active development program for advanced processes that requires four demonstration plants to be built. All of these technologies have been decribed in previous posts and can be found in the biofuels category.

[Gary Dikkers]

James,

I probably did miss the main point of your original post. You are correct -- ethanol from cellulose and ethanol from corn are two horses of entirely different colors. And ethanol from sugar cane is a third horse of yet another color.

Best,

Gary Dikkers

[C. Scott Miller]

BRI Energy is a very promising technology for bioconversion of cellousic feedstock into ethanol. Readers can learn about it at http://www.brienergy.com. Their technology partners include Katzen International and Parsons Corporation.

[John Kirkpatrick]

The discussions about using the cellulosic methodology to produce ethanol, is pure and simply just academic, as long as that process is not being used anywhere to produce ethanol. If that process is so efficient, than why isn't some really resourceful company making tons of money putting that technology to work making ethanol? Am I missing something here? Why do all the recent ethanol plants built, and being built, all use corn as a feedstock, when it is the cellulose that everyone touts as being so efficient? The article above does not set the record straight, it just further muddies the water. As long as corn is the primary feedstock for ethanol production, then arguements about cellulosic production are meaningless.

[KEN]

Why not mandate by law that all etahnol plants use renewable energy sources to distill alcohol and dry the byproducts .
Build a windfarm next to the plant .
use solar where possible for drying .

[KEN]

Has anyone calculated the bulk density of the cellulosic material used in the enzyme process . It seems that we are talking about a huge transportation issue . Stuff like switch grass needs to be baled up and hauled . Also this is not entirely free it takes large amounts of fertilizer each year to produce the cellulose .
I think we need to get off the ethanol bandwagon and go biodiesel ,a much more efficient production process and a much a much more efficient engine to use the fuel .

[TechFarm]

Good info.

I've found more recent information regarding the efficiency of Ethanol and compare Corn Ethanol, Sugar Ethanol, Biodiesel, and Cellulosic Ethanol:

Efficiency of Ethanol

[husky air compressor]

I'm working on a green house project. I'm really interested by this Ethanol Efficiency Redux and I really would like to know if it's reliable for single housing application.
thanks a lot!
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