« Technical Note: Gasification | Main | Recent News 4/12/05 »

April 10, 2005

About Ethanol

Ethanol is a renewable liquid fuel that is playing an increasingly important role in our enonomy by, in 2004:

  • Reducing emissions of particulate mater, carbon monoxide, toxic content and carbon dioxide.
  • Adding $25.1 billion to gross output through the combination of spending for annual operations and for new plants under construction
  • Reducing our dependence on imported petroleum thus reducing the trade deficit by $5.1 billion
  • Adding $1.3 billion in tax revenue for the federal government and $1.2 billion for state and local govenments
  • Rroviding nearly 150,000 jobs resulting in increasing houshold income by $4.4 billion.

The market for ethanol blended with gasoline has been driven largely as a replacement for MTBE, a suspected carcinogen, which is added to gasoline as an oxygenate and for a volume extender.  Oxygenates reduce exhaust emissions of volatile organic compounds (VOC), carbon monoxide, oxides of nitrogen and toxics.  MTBE has been found in groundwater across the US.  MTBE is currently banned in 18 states and legislation is pending in several more states.  Blends of up to 10 percent ethanol, E10, can be used in virtually all cars.   E85 (85% ethanol) can be used in flex-fuel vehicles which are readily availabe at comparable prices to standard vehicles.

In the short term, the next 20 years, ethanol could be the most important alternate fuel alleviating our dependence on increasingly expensive imported fuels.  In the longer run it could reduce the need for expensive coal liquefaction plants.  The price of ethanol has been dramatically reduced in the last 15 years and now, with 2005 prices of gasoline and with subsidies, costs about the same as petroleum gasoline.  The costs without subsidies are projected to be about the same by 2015 to 2020. 

Eighty one ethanol plants in the US, with a capacity of 3.6 billion gallons per annum, produced 3.41 billion gallons of ethanol in 2004, representing 2.5% of our gasoline supply.  Sixteen additional plants and two major expansions under construction at the end of the year will increase the installed capacity to 4.4 billion gallons per year.  Continuing the very high growth rate of ethanol production is very dependent on the price of gasoline and continued success in introducing cost reducing improvements for the production of ethanol.  We are on the verge of introducing technology that will permit economic production of ethanol from lower cost feedstocks than corn, from which most ethanol is now made.

By 2015 to 2020 the unsubsidized cost of ethanol should be the same as or lower than petroleum gasoline.  The current $0.54 per gallon subsidy is scheduled for slow reduction over the next few years until it is dropped in 2010. Subsidies for ethanol should be continued, at an a decreasing rate, until the price of ethanol is competitive with gasoline. A requirement that all new cars must be flex-fuel cars that can burn either gasoline or E85 ethanol would be a large incentive for the ethanol industry.  This in turn would be an incentive to provide more ethanol pumps at filling stations.  These incentives can be justified by the reduction in emissions, reduced dependence on imported petroleum products and a reduction in subsidies to farmers for unused land and low corn prices.

Dr Wang of Argonne National Laboratory, summary of paper, which concludes that the proper criteria for evaluating the energy efficiency of a fuel is not the net energy value (NEV) but rather: 1) to calculate the amount energy that it takes to make ethanol and compare it to the energy required to make the product that you wish to compare it to and 2) compare the amount of petroleum energy that is used to produce the two fuels.  Values of NEV have been a controversial subject, but the preponderance of evidence indicates that it is positive as Wang illustrates.  NEV indicates what fuels are most sustainable and which fuel is more environmentally friendly, but not necessarily which is better. Petroleum products have a negative NEV and probably will be even more negative as energy input for production increases with deeper wells and unconventional sources of crude are used.  The amount of petroleum products used in the life-cycle of the fuel is important because 1) as petroleum reserves become depleted it helps conserve petroleum and  2) the amount of CO2 generated is less.  Ethanol production uses much less petroleum to produce than oil.  See my post Is Ethanol an Energy Efficient Fuel? for a more detailed discussion of this topic.

Brazil is the world's largest producer of ethanol with 40% of its cars running on 100% ethanol and the rest on 22% ethanol which represents nearly 41% of the light vehicle demand, in gasoline equivalent.  The US imported 160 million gallons of ethanol in 2004, 90 million gallons of which came from Brazil.  This was largely due to shortages in US production, but we must keep our technology advancing, as Brazil has lower costs of production.  We could be a net exporter if ethanol production is pursued aggressively.

The majority of the methanol produced in the US is made from corn by the dry mill process.  This process is sometimes referred to as a sugar based biorefinery.  The steps in this process are:

  • Feedstock Preparation - The entire corn kernel or other grain is first ground into flour, which is referred to as meal.  The meal is slurried with water to form "mash".
  • Pretreatment** is used to expose the cellulose to attack by acid or enzymes.
  • Hydrolysis** uses acid or enzymes to produce sugars from the cellulose.
  • Fermentation of the sugars by enzymes and yeasts is used to make the ethanol.
  • Distillation of the resulting "beer" is used to separate the ethanol from the "stillage". 
  • Dehydration with a molecular sieve is used to remove the last traces of water thus producing pure ethanol.
  • A centrifuge is used to separate the coarse grain from the solubles.
  • Evaporation is used to concentrate the solubles to about 30% solids resulting is Condensed Distillers Solubles (CDS) or "syrup."
  • Drying of the syrup combined with the coarse grain, produces Dried Distillers Grains with Solubles (DDGS) which are are readily sold as livestock feed. 
  • The CO2 released during fermentation may be captured and sold for use in carbonated beverages and in the manufacture of dry ice.

**The pretreatment and hydrolysis steps are not incorporated into current plants, but will be required before cellulosic feedstocks can be processed, as in five plants now under development.  The technology for using these feedstocks is now emerging from pilot scale testing.  Acid hydrolysis could reduce costs by $0.19 to $0.33 per gallon according to the EIA paper "Outlook for Biomass Ethanol Production and Demand".  Enzymes that break down cellulose into sugars are still under development but, according to the same paper, when fully developed could reduce costs by three to four times as much as the acid processes.  Novozymes, the worlds leading biotech-based enzyme company, based in Denmark; and NREL announced on April 14, 2005 that they had achieved a 30:1 reduction in the cost of an enzyme to U.S. $0.10-0.18 per gallon of ethanol. Iogene has a pilot plant operating using their enzyme.  They refused to comment on their costs when I contacted them.  These developments may mean that they will be available for use in the next generation of plants. Using cellulosic feedstocks offer a potential for more byproducts than corn does which would further reduce net costs.

Extensive development of the production process has reduced operating costs significantly.  Among the items that have reduced operating costs are molecular sieves for dehydration, distributed control systems, better performing enzymes and yeasts, thermal oxidizers for air pollution control and the use of anaerobic digester to enable total process water reuse.  Using the biogas produced from anaerobic digestion to generate power is one of the next improvements that could reduce operating cost by minimizing the use of purchased electricity.

But the highest single cost is the feedstock.  Currently ethanol is made from corn and it is believed that switching to corn stalks (corn stover) will achieve significant reductions in cost, at the same time as greatly increasing the quantity of available feedstock.  Making ethanol from any cellulosic materials such as corn stover, bagasse, rice straw, waste paper, wood chips, fast growing trees, or grasses, dramatically reduces the cost while expanding the amount of feedstock available.  One big advantage of these sources is that they significantly reduce the amount of land required to grow feedstock.  Corn grown for ethanol now uses 11% of corn production and expansion to produce all future requirements from corn is not possible.

The other major development that is being pursued is the "thermochemical biorefinery" which I will describe in a future post.

If you would like further information on ethanol and ethanol process development these three references are suggested:  Fuel Ethanol, A Technical Evolution, The Office of Biomass Program's Mutiyear Plan 2003 to 2008 and "How Ethanol is Made".

April 10, 2005 at 10:35 PM in Biofuels | Permalink


TrackBack URL for this entry:

Listed below are links to weblogs that reference About Ethanol:


Minnesota is leading the way in ethanol fuels, especially E85. The state now has 120 E85 stations, far more than any other state. See how the American Lung Association of Minnesota is helping to promote this cleaner-burning alternative to gasoline:

www. CleanAirChoice.org

Posted by: Bob from the Lung Association | May 6, 2005 02:18 PM

Regarding using enzymes to break down cellulose for ethanol production: A canadian company, Iogen Corporation, has developped and demonstrated a workable process to do just that. Check it out:


I have contacted Iogen to see if they can give me any further information than they have on their website. I am waiting to see if I get a reply before I make any further comments.


Posted by: Trent | April 14, 2005 04:21 PM

Can I get some reassurance on the net energy loss thing? I think that's my biggest fear where ethanol is concerned.

Posted by: praktike | April 14, 2005 01:18 PM

Hitting EROEI again, I've seen calculations finding that ethanol production gives a net energy loss. So, is this true under current production methods, and if so can the new processes you describe turn it around?

Posted by: Jim Lund | April 14, 2005 12:20 PM

I'm interested in a reference for your numbers on US production (2.5 percent)...

Also, what is your opinion on the controversy regarding ethanols low EROEI?

In other words, if you kick natural gas and petroleum inputs out of the picture, (and subsidies, of course), how many acres of corn or cellulose are needed for production, and how many acres do you net for external use?

This is important if we want to substantially replace liquid fuel with ethanol, or even 10% of our current consumption.

Posted by: Jon S. | April 13, 2005 01:05 AM

Post a comment