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New Life Cycle Study Concludes That Biomass for Ethanol Is Not the Most Advantageous Energy and Emissions Use of the Feedstock

A new life cycle study assessing the benefit of cellulosic ethanol in the context of projected feedstock constraints concludes that in terms of reducing greenhouse emissions and fossil fuel dependency, more is lost than gained when prioritizing biomass or land for bioethanol, rather than for use in technology pathways involving heat and power production and/or biogas, or natural gas and electricity for transport. The study was published online in the journal Environmental Science & Technology on 4 October.

The study by researchers in Denmark begins with the conclusion that toward 2030, the amount of biomass which can become available for bioethanol or other energy uses will be physically and economically constrained, regardless of whether of global or a European perspective is applied. This implies that the use of biomass or land for bioethanol production will most likely happen at the expense of alternative uses.

Specifically, the study compares the use in transportation of cellulosic ethanol produced from whole-crop maize by fermentation in several process configurations to alternative use of the feedstock in heat and power applications fueled by coal or natural gas.

Among the scenarios investigated, the researchers found that using willow in CHP production combined with using electric cars for transport yields the highest GHG mitigation and reduction in oil dependency.

They also found that the optimal biogas scenario is for biogas to substitute for natural gas in heat and power production and to use the displaced natural gas to substitute for oil in the transport sector.

In terms of greenhouse gas emissions, the ethanol baseline scenarios provide by far the lowest net GHG mitigation compared to the alternative utilizations of land for energy purposes. For example, use of the land to produce willow used for combined heat and power in substitution for coal provides GHG mitigation more than twice and high, and even higher if combined with electric cars.

Even when using fodder byproduct as fuels, the ethanol scenarios are still compared to the alternatives. The researchers attributed the low net GHG mitigation in the ethanol scenarios to the considerable amounts of steam and electricity consumed in the process of converting biomass into ethanol, especially for pretreatment, hydrolysis, extract concentration, distillation, and drying processes.

Less energy is required for catalyzing anaerobic digestion in the biogas process, for the thermal gasification of willow, or for wood pellet manufacturing. Other factors contributing to the difference in GHG mitigation across the scenarios include the high CO2 content of coal, which results in large GHG mitigation when biomass is used to displace coal, and the high energy efficiency of electric motors compared to combustion engines.

The ethanol scenarios also provide a low net fossil fuel displacement compared to several of the alternative technology pathways. Up to 2.5 times as high oil savings can be obtained with the alternative energy crop utilization pathways, for example.

Overall, for the case presented, the reductions in GHG emissions and fossil fuel dependency, obtained by producing whole-crop maize for bioethanol production happens at the expense of other land/biomass utilizations, which would provide considerably larger reductions. Thus, for this technology case and perspective, more is lost than gained when prioritizing land/biomass for bioethanol.

This is mainly caused by the significant energy conversion losses in bioethanol production compared to use of biomass in the energy sector. The losses lie in the need for pretreatment (lignocellulosic based production), the relatively low fermentation yield of ethanol, the need to dry and further process the byproduct and residual unconverted matter in order to make use of them, and the need to separate ethanol and water, implying distillation in all known cases. Such losses are not present in alternative technologies, e.g., biomass conversion to electricity and/or heat by incineration or conversion to biogas.

As long as fermentation-based conversion of biomass to ethanol implies these losses, bioethanol will come out disadvantageous to the alternatives studied heres and this is the case for presently known bioethanol technologies including both starch and lignocellulose based production. Thus, the results question the assumed justification for lignocellulosic fermentation based bioethanol: instead of reductions in GHG emissions and fossil fuel dependency, net increases will much more likely be the outcome, when considering the alternative biomass/land utilizations deprived on behalf of bioethanol.

—Hedegaard et al. (2008)


  • Karsten Hedegaard, Kathrine A. Thyø, and Henrik Wenzel (2008) Life Cycle Assessment of an Advanced Bioethanol Technology in the Perspective of Constrained Biomass Availability. ASAP Environ. Sci. Technol., doi: 10.1021/es800358d


Kum Dollison

While it's true that, in the loooong run, producing biogas is more efficient than ethanol, the U.S. is, Today, powering the equivalent of 20 Million automobiles with the 10.6 Billion Gallons of ethanol it's, presently, producing.

With Non-Opec having already peaked, and Opec being not far behind our primary challenge, Today, is fueling the 240 Million vehicles on the road, at present.

We'll probably "ease" into the biogas thing with "fleet vehicles," initially.


Could it be that in our desire to keep our oversized gas guzzlers running with bioethanol intead of fossil fuels we are, once again, taking the wrong path?

Partial, followed by complete electrification of our vehicles and HVAC with clean electricity seems to be the best route.

We do not need more risky expensive OIL wars and financial turmoils.

Let us investment instead, in new clean technologies to locally produce more clean electrical energy and to locally mass produce PHEVs, BEVs and fully electrified high efficiency HVAC systems for our homes.

There are no acceptable reasons why USA should have to import OIL, NG and Electricity after 2020.

It is time to wake up.

Roger Pham

This is exactly the point I've been making all along. Extracting H2 and methane from waste biomass is the most efficient way to harness this renewable and storable source of energy. This energy supply is quite limited so one must make the most efficient use of it.

Convert the waste biomass into a dense and easily-transportable form, and then gasify this form into H2 only when demand arises at or near the site of H2 distribution. H2 in FC and in an H2-optimized ICE is far more efficient than current ICE SI technology. However, until the H2 economy will arrive, bio-methane can be used as a bridge or stop-gap solution in the current transportation sector.

Methanol synthezized from the gasified biomass would also be efficient, but it is too corrosive and toxic for mass utilization. Ethanol, whether from grains or cellulosic, should be reserved for human consumption! :)

Rafael Seidl

@ Roger Pham -

why bother with hydrogen at all? Compressed or adsorbed natural gas will do nicely for next few decades, especially in Europe and if biogas is used to produce heat and electricity.

Alex Kovnat

As a result of the above conclusion that ethanol is not the best choice to meet our energy needs, one might ask: Should we be sorry about all the effort that has gone into ethanol up to this time?

My answer is no, and I'll explain why:

During the 1990's, we were making extensive use of methyl tertiary butyl ether (MTBE) as an oxygenated gasoline additive, to meet regulatory requirements for a little combined oxygen in gasoline to reduce hydrocarbon and carbon monoxide emissions.

MTBE did the job well. It blended with gasoline very nicely, had a very good octane boosting effect, and didn't adversely affect Reid vapor pressure, which has a bearing on evaporative emissions.

Unfortunately mother nature threw a frustrating showstopper in our faces when MTBE started turning up in water wells and surface waters. So, it was back to square one. We needed an oxygenated compound to meet the requirement I described above, and also we needed an octane enhancer. The oil-automotive industrial complex was also under pressure to use renewable resources.

Enter ethanol. Since fermentation is a part of mother nature's scheme of things, she doesn't object to ethanol. And, it has good octane rating. Ethanol is less corrosive than methanol, and doesn't create (at least not to as great a degree) the problems you get when you blend methanol into gasoline.

Finally, unlike compressed natural gas, ethanol can be used without extensive modifications to existing automotive designs.

So all in all, ethanol was the best we could do up to now. Should we consider using compressed NG instead? Unquestionably. As natural gas engines tend to be less pollution-intensive than Diesel engines, we are seeing more use of CNG in buses and commercial vehicles. In 1983 I was at a Society of Automotive Engineers dinner meeting where the topic was Ford's natural gas pickup truck. Ford has since decided to emphasize hydrogen.

Given that natural gas doesn't require as high a storage pressure as hydrogen to get the same range, I hope it will be possible to attain whatever emissions reduction performance (especially nitrogen oxides but also other hydrocarbons, particulates, and carbon monoxide) we need, without having to resort to hydrogen.

Before I sign off I'd like to add that I hope we can improve the efficiency of processes to produce ethanol from biomass. Liquid fuels tend to be less of a packaging (i.e., space) problem than gaseous fuels, which have to be stored under high pressure. Perhaps the free market and not government arbitrarily choosing winners and losers, is the best way to determine what fuel is best for various applications.


Well duh! This is such a no brainer I got to wonder why we're not doing this instead of going with ethanol... Oh wait, that's right, we've got leaders with no brains.

tom deplume

This study quantifies what I've said in the past. The most bang for the biomass buck comes from using it as a replacement for coal then using some of that electricity for EVs. Using biomass for IGCC is even better.

Roger Pham

Hi Rafael,
Agree with you that adsorbed CNG will do nicely for the next few decades, that is, until FC technology and adsorbed H2 storage technology will be perfected and priced affordably, since FC promises nearly double the thermal efficiency of NG-ICE.


Automakers really like ethanol because its dense (enough) and very easy to use with their existing technology (IC engines). Only about $50 more per care is needed to augment an existing car line to use E85.

I think range issues with PHEV-methane vehicles could be addressed by going tri-fuel and having a small E85 tank as well.

As with hydrogen, the automakers will avoid discomforting themselves if at all possible, even if it means pushing expensive, inefficient technologies up higher in the fuel production process.

I can see this inefficiency (at the expense of the consumers) being somewhat difficult to unwind in the near term. (Maybe Pickens should be supported to the extent that it serves this end?)

SOFCs using NG might make things more interesting as well.

"...assessing the benefit of cellulosic ethanol..."

"...ethanol produced from whole-crop maize by fermentation..."

Maybe I am misunderstanding, but the term "whole-crop maize" does not sound like cellulose ethanol.

"As long as fermentation-based conversion of biomass to ethanol implies these losses.."

They seem to mix things. There is grain fermentation and cellulose preparation and fermentation. As long as you go that route sure.

But if you gasify the cellulose biomass, you can make methane, methanol, ethanol or other hydrocarbons without fermentation.

nrg nut

Keep in mind that NG is a petroleum-based business-as-usual scenario while cellulosic is entering the market via a wide variety of non-petroleum producers.

The old adage "Follow the money," applied here would indicate a pattern of oil and gas industries trying their damndest to limit entry of any non-petroleum energy resource.

The transition to non-fossil fuels is open to all offerings. And though NG and coal want to polish their image to be included in the "clean" energy cycle - the facts remain they are non-sustainable resources controlled by entrenched energy companies. Coal-bed methane wells in British Columbia are scarring pristine forest/valley habitat posing far greater environmental damage than the apparent difference in GHG release.

Ethanol has worked well in Brazil using cane feedstocks claiming 1:8 energy input. Coskata and Range Fuels and other entries in cellulosic from waste offer the real probability of low cost alternatives to fossils. Can we afford to nitpick efficiencies while petroleum pushes us into yet another energy monopoly? We think not.

Kit P


Thanks for the informative post.

“As a result of the above conclusion that ethanol is not the best choice ..”

Can you tell me what country the biomass is produced in from reading the LCA?

Alex Kovnat

@Kit P:

I can only speak from the perspective of the American experience. If the lead article was from Europe, maybe they have a different set of conditions. For example, they might not have as much of an issue with MTBE as we in America have. Also in Europe they have a higher percentage of Diesel cars, so bioDiesel might be a better option for them.

And then too, there are probably more natural gas vehicles, so biomethane might be a more logical choice for Europe than here in America.

There has been criticism of the American ethanol effort. One hopes that this was mainly due to the fact that first-generation ethanol plants were glorified whiskey stills, and that the most recent designs are more efficient.

We'll have to wait and see what happens with the cellulosic ethanol facilities now under construction. Novozyme seems to have a good handle on the enzymes issue involved with breaking down cellulose.

I've been interested in alternative fuels for over 30 years. At one time I was fascinated with the idea of gasoline and other liquid fuels from coal, but that may not be a good idea now that carbon dioxide has become such a hot issue.

Whatever, I'll keep reading Green Car Congress.


I think you get about twice the fuel (energetically) when producing biogas (methane) from biomass compared with producing ethanol. And this doesn't take into account the added energies needing to produce ethanol (drying, distilling, etc.) so the overall disparity is probably even worse. The costs of the cellulosic ethanol production facility can't be discounted either. That said, a liquid fuel is much more convenient than a gaseous one.

Interesting for them to comment on burning biomass to produce electricity, which is then used in cars (I think that's what they meant). If burning biomass to make electricity is 30% efficient, then you are already beating the IC engine. The grid/transmission losses would be easily trumped by the processing and energy costs of the ethanol production.

Reality Czech
If the lead article was from Europe, maybe they have a different set of conditions. For example, they might not have as much of an issue with MTBE as we in America have.
Not using MTBE gets rid of the issue. MTBE was a response to a government demand for oxygenated fuels in the USA, not Europe.

I agree that ethanol was and is an EXCELLENT replacement for MTBE, which was found to be too long-lasting when released into the environment.

MTBE (a chemical produced by the petroleum industry) was added to gasoline for cleaner emissions. American emissions standards have tended to be cleaner than European standards, which partly explains the lack of diesel engine penetration for autos in the U.S. After MTBE was found to be problematic, ethanol was used instead.

But it should be mentioned that there is big difference in 10% ethanol for emissions improvement, and 85% ethanol for the purposes of oil substitution. The economics of the two prospects, as well as the quantities involved, are completely different.

The fact that ethanol makes sense as a fuel additive doesn't mean it necessarily makes sense as a fuel substitute.


There is an interesting closed loop ethanol scheme using the methane from livestock manure to power grain -> ethanol production. The operation claims a 1:45 energy ratio.

Kit P


I am astounded at the progress biofuels have made in the US in the last few years. However, there is a lack of LCA data using recent process numbers. Clearly, using biomass instead of oil for a district heating CHP is a winner when there is limited biomass like US and EU cities..

In the US we have lots more biomass than we have district heating. We will nominate ai_vin to live next to the power plant to save the planet.

The US is a very large and diverse country. There many many locations where different technologies would be the better choice.


Not only biogas is more efficiently produced from biomass than ethanol but also it can be burned with a much better efficiency in an ICE thanks to very high octane index and gazeaous form, last but not least it is the least carboneous of all HC fuel and by fara the cleanest, what else can we ask ?? ha yes no complicated development since the process of methanisation is not new at all it can be produced at the farm then minimisation the transportation of biomass (prooblem that will plague the cellulosic ethanol) , but it requires a new infrastructe to transport an distribute that gas.


The bio methane can be put into existing natural gas lines. Just locate the plants near the farm fields and natural gas mains. It will clean up the present natural gas content. It is pure methane without the propane, butane or other substances.

black ice

As I have said this before, hydrolysis and fermentation are definitely not the most energy efficient use of lignocellulosic biomass. This is because, first, cellulose is a natural plastic that is practically unsusceptible to any low energy treatment like hydrolysis, and second, its content is only like 70 % on average in the lignocellulosic feedstock, the rest being lignin. These factors make it not suitable for fermentation to ethanol whatever clever scheme one might devise.
The most efficient way to deal with lignocellulosic biomass is thermochemical route. This includes combustion for heat production, and gasification. Gasification is particularly attractive because it yields gas that can be used for electricity production via a thermal engine, and can efficiently be converted into liquid fuels and chemicals.
Of course, there are feedstocks that are best fermented to methane even though carbon conversion will not be that high.


The real issue is that is not so easy to switch from one primary fuel source to another in case you try to make primary fuel accepted in automobile directly. That is very long lasting, expensive and tiresome process. You have to consider your strategy very carefully. And vice versa – it is not so complicated switching fuels for power generation. You just need to build new power plant which you would build in any case. It is just matter of consideration which fuel do you prefer. Therefore in order to be able to keep hands free and be able to switch to any fuel very quickly – coal, biomass, wind, NG, solar, nuclear or even fusion there is no other opinion to PHEV or BEV. You can charge in your battery which ever fuel is most economical, rational or “green” at any time!!! And this freedom of choice is just round the corner....

Jeff Baker

People who are losing their jobs, their homes, and in some cases their families, could care less right now about how “environmentally correct” ethanol is or isn’t. We are paying for an oil war sucking up $200 Billion a year and squandering 3% of our fuel supply. Add that to the price of your gasoline, diesel fuel, and your airline ticket. Our $500 Billion a year Foreign Oil Trade Deficit is paid for with debt instruments that we pay interest on. Thus, there is a Hidden Cost for fuels derived from imported oil. Stimulating Domestic Biofuels has a 10 to 1 payback, because it eliminates this “hidden cost” and stimulates our economy. Reducing our consumption of foreign oil has a higher priority than our carbon footprint.

A study by Iowa State University documented that ethanol lowers the cost of gasoline by 29 to 40 cents per gallon, which saves consumers $40 to $60 Billion a year and reduces imported oil. Our vehicles don’t run on biomass pellets or biogas, unless you want to spend $5-10K to convert them and fill them at home. Then spend extra time and expense finding a place to fill-up. No infrastructure.

There are two branches of auto-vehicles: (1) The 240 million vehicles we now have on the road valued at $6 Trillion, running on liquid fuels, which we will not be throwing away just yet. (2) And future vehicle designs that are under development, such as electric and plug-in hybrids, which will take 20 years to replace conventional vehicles. I agree that running electrics and plug-ins charged with electric power is the way to go. Electric is 1/7 the cost of operating a conventional vehicle. But in the mean time, we need Domestic Liquid Transition Fuels for the conventional vehicles we are phasing out.

The study described above is somewhat true but also flawed and inadequate. We are already using biomass burn power plants and converting some coal plants to biomass. We are already converting municipal solid waste, sewage and livestock manure into biogas for fuel and electric power. The authors are definitely not fully knowledgeable about ethanol, which now only consumes 23,000 BTUs to refine per gallon. Also, there are numerous sources of ethanol, and they’re all different: 2 to 1 Corn ethanol plus byproduct feed. 3 to 1 cattail ethanol plus biomass. 4 to 1 Sweet Sorghum based ethanol plus biomass. 5 to 1 cellulose ethanol, such as 30 ton miscanthus. 6 to 1 Jerusalem artichoke plus biomass. 7 to 1 integrated dairy: biogas, biodiesel, ethanol, plus milk and feed. 10 to 1 Algae based biodiesel, ethanol plus feed. And the list goes on. We have super sorghums that produce 40 tons per acre, and algaes that produce 100 tons per acre. And you can figure 100 gallons per ton ethanol. Yet the study uses “whole crop maize”. Get Real.

Cellulose ethanol does not consume natural gas or coal. It is self-powered from biomass, lignin or synth gas, depending on the process. Also many conventional corn ethanol refineries are switching to low heat distillation processes, biomass burn CHP, and renewables for production power. Efficiency evolution.

We do not have a food shortage or a shortage of land. We only use about 1/3 of our arable land, and we have millions of acres, not suitable for food crops, to grow biomass on. We fulfill all the orders for grain exports and could export more. This year we exported 20% more feed corn and double the amount of distillers grains livestock feed, after years of flat exports. If you count municipal solid waste and sewage, we have a billion tons of biomass waste available.

We are still discovering what ethanol can do. For example, Hydrous Ethanol: We can mix 4-5% water with ethanol and still blend it with gasoline. Or, we can eliminate gasoline altogether and blend ethanol only with water. Phil Ratte (Mechanical Engineer, BME University of Minnesota): “From 1981 to 1989, I worked with Herb Hansen, who had been an engineer on a WW II submarine, and a former captain of a nuclear submarine. We developed two prototype cars, a Ford Pinto Station Wagon and a Mitsubishi Sedan, that ran as well on 65 proof ethanol (2/3 water and 1/3 ethanol) as they did on unleaded regular gas.”

“Not only biogas is more efficiently produced from biomass than ethanol but also it can be burned with a much better efficiency in an ICE ..”

“The bio methane ...”

It is very obvious that Treehugger and sjc do not understand the engineering challenges with using biomass for energy.

Here is an example of good ideas: AGSTAR is a very successful program to reduce ghg and produce energy.
Producing biogas requires good engineering and experts to operated them.

Biogas is a dirty and low BTU fuel that is very a good stationary boiler to produce process steam. Clean biogas up a little bit to remove things like H2S and it can be used properly designed stationary ICE to drive a generator and make electricity for the local grid.
Clean biogas up a lot to produce pipeline quality methane, it can be compressed and put in a pipeline so Treehugger and sjc can burn it to make electricity in their backyard.

How green is that?

Here's the deal. If you are going to do something hard why not make ethanol? For those who did not take the time to look at gr's link go there and watch the video. The Mead facility is textbook industrial ecology. The most efficient use for biogas is too make process steam to make ethanol.


Would it be possible to use the idea of vertical farming to grow large volumes of willow/hemp/bamboo on the exhaust stacks of CCGT / IGCC power stations with the resulting biomass being co-fired with the fossil fuel or turned into bio char.

Small natural gas powered range extenders for electric vehicles would double nicely as distributed combined heat and power units

Digestion of all suitable waste streams with some specialised crops could contribute a replacement for natural gas.

Concentrating solar for peak cooling requirements, efficient heat pumps powered by wind power for heating. Improvements in building insulation and thermal mass to reduce heating requirements in the first place.

The largest chunk of energy usage goes on heating / cooling and transport this is where the biggest efficiency savings are.

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