Ethanol from Biomass: A Sustainable Option?

The Promise of Cellulosic Ethanol

I have mentioned a couple of times the research I was involved in during graduate school. I have provided a couple of links (under “Links”) that describe this research in detail. Briefly, we were trying to turn biomass (switchgrass, corn stover, wheat straw, and municipal solid waste) into ethanol and various organic acids and ketones. Biomass consists of many organic components, but it is primarily the cellulose component that gets turned into ethanol, hence the term cellulosic ethanol.

Cellulosic ethanol has two major advantages, and one major disadvantage over ethanol from grain. The first major advantage is that large fossil fuel inputs in the form of fertilizer are not required to produce the biomass. Therefore, cellulosic ethanol has a much better energy return on energy invested (EROI) than grain ethanol. The second advantage is that the feed stock will be cheap, or even free (in the case of municipal solid waste, you can earn money by just accepting the waste). The disadvantage, however, is the reason cellulosic ethanol has yet to make a major impact. The enzymes required to free the fermentable sugars from the cellulose are very expensive. Historically, these enzymes have added as much as $5.00 a gallon to the cost of producing cellulosic ethanol. (1) However, substantial R&D efforts by a number of companies have brought the costs of these enzymes down to around $0.30 per gallon of ethanol.

One idea that I had in graduate school was the use of termites to do the conversion in our bioreactors. To my knowledge, I was the first person to ever try this. I got some butanol by doing this, but with a very low yield. The reactor probably also made methane, but we only looked at the liquid products. Perhaps if I could have very accurately replicated the termite gut chemistry I could have gotten yields up. It still makes sense to me that since termites are so efficient at converting cellulose, that would be a good place to look for a template organism for a bit of genetic engineering. It was my opinion then, and it is my opinion now, that the future of cellulosic ethanol hinges on genetically engineered microorganisms.

It is safe to say that while the gap has narrowed, cellulosic ethanol is still more expensive to produce than grain-ethanol. However, barring the kind of quantum leap I discussed in my previous essay, grain-ethanol has little upside potential. In addition, even if we turned the entire U.S. corn crop into ethanol, it would supply no more than 10% of the current fuel demand in the United States. (2) Given the facts that 1). The energy balance for grain ethanol is not that great; 2). We don’t grow enough grain to significantly lower our fossil fuel usage by turning it into ethanol; 3). Soil is eroded and fertilizer and pesticide runoffs contribute to water pollution as a result of large-scale corn farming; one wonders why this is even a topic worthy of discussion. Forget grain ethanol. If the government is going to force ethanol into the fuel system, make it cellulosic ethanol. I for one don’t mind paying $0.30 more a gallon for something that actually has a chance to be sustainable. However, many projections indicate that cellulosic ethanol will cost substantially less than grain ethanol in the not-too-distant future. A story in Business Week last year (3) reported:

Last December the bipartisan National Commission on Energy Policy released a report, Ending the Energy Stalemate, that analyzed the potentials of various alternative fuels, including both types of ethanol (which is just an industrial grade of alcohol). Only cellulosic ethanol got a decisive thumbs-up. By 2020, the commission predicts, its production cost could be less than 80 cents a gallon. In stark contrast, after 20 years producing grain ethanol, it still costs $1.40 a gallon to produce — roughly twice as much as gasoline.

Is This Enough to Ensure Sustainability?

Let’s not kid ourselves. It is going to take more than all the ethanol we can possibly produce to replace our current usage of fossil fuels. I watched a CNN special a week ago on the topic of peak oil. Frank Sesno visited Brazil, where they make ethanol from sugar cane. When it was explained that Brazil is supplying much of their own fuel from homegrown ethanol, Sesno asked “Why isn’t the U.S. doing this?” There are a couple of things that Sesno apparently missed. First, sugar cane is the optimum crop for producing ethanol, because the ethanol yield per acre is about twice what you can get from corn. Unfortunately, there are few areas in the U.S. that are ideal for sugar cane production. Brazil is currently exporting ethanol to the U.S. and Europe, and they can ship it to the U.S. for cheaper than we can make it here. (So, we slap a tariff on it to make sure they can’t undercut our corn-ethanol producers). The 2nd thing Sesno apparently didn’t notice was all of the compact cars on Brazil’s roads. They showed a clip of him on the highway, and every car on the road was a compact. Therefore, their per capita fuel demand is far lower than ours.

To put the U.S. situation in perspective, consider a recent article on sustainability in Sweden. (4) The Swedish government has set a goal of being totally independent from oil by 2020. The article reports that today, Sweden only relies on petroleum for 34% of their energy needs, and renewable energy supplies 25% of their energy. However, Sweden relies heavily on Brazil for their ethanol:

Today the most effective source of ethanol is sugar cane. Brazil produces ethanol from it and Sweden obtains most of its ethanol from Brazil. But the country also already produces a fourth of its ethanol from Swedish wheat. Neither system is fully satisfactory in terms of energy output and the effects on the environment involved.

Sweden’s highways, like the rest of Europe’s (and Brazil’s), are dominated by small, fuel-efficient cars. Given that 1). Sweden is far ahead of the U.S. in their march toward energy independence; 2). Their government has made a serious commitment toward energy independence; 3). Petroleum is already a minor contributor toward their energy needs; 4). Renewable energy already supplies 25% of their energy needs; 5). Their per capita energy usage is much lower than ours; and 6). They think it will still be 2020 before they achieve energy independence; it should be clear just what a pipe dream energy independence is for the U.S. at the moment. Barring a concerted effort at conservation in the U.S., we don’t have a prayer of energy independence. We simply won’t be able to make enough ethanol to meet our demands. A combination of renewable sources might be able to meet our current needs, but it is going to require a huge effort on our part. Even then, at some point we are going to have to come to grips with sustainability. That will be the topic of an upcoming essay.


If ethanol is going to be mandated into our fuel supply, we will be far better off utilizing waste biomass instead of grain. The energy balance is more favorable for cellulosic ethanol, and it is projected to have the potential to compete with gasoline without the need for subsidies. However, due to our very high per capita energy usage, we are kidding ourselves to think that we can meet our needs with renewable energy unless we reduce our consumption.


1. Creating Cellulosic Ethanol: Spinning Straw into Fuel

2. The Money-Grubbing Mendacity of the Ethanol Lobby

3. Not Your Father’s Ethanol

4. Sweden Plans Wood-fueled Future

14 thoughts on “Ethanol from Biomass: A Sustainable Option?”

  1. Thanks for the compliment, Andrew. It means a lot. I had put off starting a blog for a long time, because I thought that there were so many out there, nobody would ever read it. I am glad to know some people are reading it.


  2. Excellent again Robert,

    I agree it would be a mistake to attempt to draw too many parallels between the Brazil experience with ethanol and ethanol in the U.S. There are several reasons why we can’t do what Brazil has done:

    1. As you mentioned, the sugar from cane is much more efficient for making ethanol than the starch from corn.

    2. Brazil has vast tracts of undeveloped land with the type of soils conducive for growing cane.

    3. That Brazilian land is at the tropical latitudes suitable for growing cane.

    4. Brazil has an abundance of dirt-cheap, machete-swinging laborers. (A condition I doubt we want to exist here.)

    And you mentioned a fifth that had not occurred to me: Brazilians are much more frugal in their use of energy than we are, driving mostly compact cars that consume less energy to push themselves down the road.

    The last is particularly significant. I lived in Germany for 11 years, and always marveled at how their per capita energy consumption was about a third of what it is in the U.S, yet their standard of life was just as high as ours.

  3. Yeah, cheap labor is an important factor in Brazil’s ability to crank out cheap ethanol.

    I know what you mean about Germany. I lived there for 2 years. I was always amazed at their energy usage. But, there are no pickups or SUVs on the roads there.

    We could also take some lessons from them in land usage. Driving around the country, you would never guess that the population is over 80 million. They have so much rural land that it just doesn’t seem possible. They have just not allowed the kind of sprawl that has taken place in the U.S.


  4. From a brazilian friend: So, why not you americans turn out also more frugal with gas consume? You really need SUVs? Europe no. Japan no. England people love bicycles!But you banked theocratic dictators like the Arabian Saudis (the true reason why Osama Bin Laden hate you), invade Iraqi (nurturing a new champ for terrorists) and expose your youg to death (more than 2400 by now, isnt?) only because you cannot live without SUVs? Sorry for you…

  5. So, why not you americans turn out also more frugal with gas consume?

    The reason goes back to the early oil discoveries in the U.S. Oil was plentiful and cheap, and it looked like it would last forever. So, we built a society around cheap oil. Our cities reflect this, as we built them with a lot of suburbs and sprawl. Most of the country is addicted to this lifestyle, so when oil starts to get expensive, we demand that our politicians do something about it.

    Since we are a democracy, and politicians have to worry about getting themselves reelected, they have never had the collective courage to implement policies that would significantly reduce our energy consumption. So, we are heading toward peak oil in the next few years, and I think the general public is oblivious to the fact that this will force them to finally conserve.

    I think our descendents will look back on our wasteful use of oil during the past 100 years and be amazed that we didn’t put more effort into conservation.


  6. The last part of your link was chopped off. It should be “E85background.asp” for anyone who wants to check it out.

    I am familiar with the website. My first essay addressed some of the claims. For example, the claim that the net energy balance is 1.67 is flat out false. That myth has been perpetuated by an invalid accounting practice that the USDA employed. I detailed this in my first essay on grain-ethanol.

    The claim that the net energy balance of gasoline is 0.79 is also ludicrous, and is also dissected in my earlier essay. Think about it. Would they really need subsidies and mandates if the energy balance was so much better than for gasoline? In reality, comparing apples to apples, the energy balance on gasoline is at least 750%. They leave out the step where it takes only one barrel worth of oil energy to extract 10 out of the ground. If I calculated the ethanol energy balance the same way they do the one for gasoline, I would get an efficiency of about 30%, versus the 79% for gasoline.

    The quote about reducing foreign oil imports is highly exaggerated. As I showed earlier, because of the poor energy balance it takes 6 gallons of ethanol production – subsidized at over $4.00 – just to create the energy contained in 1 gallon of gasoline. The same goal could be accomplished – at much less cost – by just raising the taxes on gasoline. But the ethanol subsidy is a stealth tax, so it is more palatable, I suppose.

    So, yeah, in a nutshell, the USDA is wrong. They have an agenda, and are selectively using statistics to push that agenda. I have engaged them in e-mail conversations (the authors of the paper quoting the 1.67 energy balance) and they didn’t even try to defend themselves. They just deferred to “someday when cellulosic ethanol can compete with gasoline on a level playing field”. Hey, I have no problem with that. Subsidize cellulosic ethanol then. But don’t subsidize the wasteful practice of producing ethanol from corn.


  7. To our friend from Brazil,

    You are absolutely correct; we should be more frugal burning energy.

    I did some research today and found we are real energy hogs compared to you.

    * The total average per capita energy consumption in Brazil is 36.3 x 10^6 BTU/person/year.

    * The total average in the United States is 209.7 x 10^6 BTU/person/year.

    We use almost six times as much energy per person as you do.

    It’s even worse with respect to the energy spent on transportation:

    * Brazil spends 11.6 x 10^6 BTU/person/year for transportation.

    * In the U.S. we spend 88.7 x 10^6 BTU/person/year for transportation.

    As Robert pointed out yesterday, that explains a great deal of the reason you can be self-sufficient on cane ethanol. You need only 1/8 the energy we use to move around. If you used eight times as much energy for transportation, you woudl probably need to import oil too.

    If we got our per capita energy use for transportation down to your level, we probably wouldn’t need to import oil for gasoline.

  8. Since 7 Deadly Sins is too threatened by other people being able to state facts to accept anonymous comments, could you please tell him that Tom Still is NOT the press. Tom Still is a wholly owned subsidiary of the UW. The UW, by the way, is currently researching a bacteria to more cost effectively and efficiently turn saw dust and wood chips into ethanol. Pretty easy to see that Still has a fiduciary conflict of interest……….

  9. Hi Robert,

    I’ve enjoyed reading your posts. I’m curious about how you think the cellulosic ethanol story will play out…

    Cellulosic ethanol can come from two sources- dedicated biofuel-crops, and agricultural waste. Conversion of waste to ethanol (assuming good ROEI) I guess is a no-brainer. However how much of this waste is there?? Then, if biofuel-crops are grown, such as switch grass, how much land area do you think would be used, given competition with food crops and animals?



  10. Ben,

    Thanks for stopping by. I think you hit on what will happen. I believe we will start making it first commercially from waste. This is exactly what I did in graduate school. The cost of the enzymes needed to convert the cellulose has come down substantially, but still needs to come down a bit more to be competitive. I think things like switchgrass are still farther in the future.

    I still think, due to land constraints, potential yields, the lower BTU value of ethanol, and the superior characteristics of the diesel engine, biodiesel is the area we need to focus on for our liquid fuel needs.


  11. It will definitely make the most sense to first produce cellulosic ethanol from waste, such as municipal solid waste, waste from paper factories, and any plant that produces cellulose waste.

    I have seen some arguments that suggest that planting any dedicated crop, even switchgrass, does not have a great energy return. I haven’t been able to study the inputs in close enough detail to say one way or the other.


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