DOE Awards Novozymes $12.3M to Increase Efficiency of Enzymes for Cellulosic Ethanol Production 2x
China Has 168M Motor Vehicles on the Road

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


Don T

At least one person on this string of comments actually seemed to have read the journal article...

The authors are talking about Corn stover. Cellulosic ethanol is usually envisioned for wood chips and switch grass with some agricultural residues.

Of course corn stover ethanol does not make a lot of sense to address all of our needs. Shame on green car congress, that was a misleading article and not clearly presented.


Seems to be some pushback from ethanol supporters.

Say what you want, but 2 facts remain evident:

1) You can get much more energetically from a given amount of biomass with biogas than you can with ethanol. And with less physical plant overhead and less (added) energy input.

2) Given our thirst for oil, biomass resources are likely to be limited, not unlimited.

Again, no argument that liquid fuels are more easily stored and carried than gaseous ones. But if the liquid fuel costs twice as much, perhaps the customer would prefer a gaseous tank storage. It's not clear what's best for the consumer, but it is clear what's best for the ethanol producers (and biogas producers, for that matter).

nrg nut


Your second point is important. Because biomass is not unlimited and there are costs to conversion and transportation. Bio-methane, in any scenario going forward will be a supplement to the huge installed NG infrastructure. That infrastructure is owned and operated by the petroleum industry.

Oil will pay lip service to a "bio-methane" expansion for CNG vehicles, knowing full well that their market share via coal-bed methane wells will grow.

The downside of the Pickens Plan is his insistence that we convert/manufacture cars to CNG. 99% NG comes from oil field operations. Any bio-methane industry will be dwarfed by the installed oil and gas infrastructure and its expansion will expand our reliance on fossil NG.

While there are some advantages to bio-methane from an engineering perspective - it is a poor political choice. At least for now.

david e bruderly

The renewable liquid and battery electric fuel pathways have plenty of policy support, in the form of mandates, incentives and grant subsidies, and this policy support has stimulated hundreds of millions in capital investment in RD&D and production and distribution infrastructure. The gaseous fuel pathways, however, have been badly neglected by federal and state policy, not to mention funds for RD&D and incentives to stimulate capital investment. Like E10 natural gas motor fuels in the form of CNG offers a renewable fuel pathway via both biomethane from waste AND blended natural gas/renewable hydrogen motor fuels for use in existing internal combustion engines. The few vehicles using these nethane/hydrogen mixtures have been branded with fancy names such as Hythane, HY5 or H20. But the technology itself is universally available -- and affordable.

Jeff Baker

From the unnamed above post: “The most efficient use for biogas is to make process steam to make ethanol.” Good Point. This is what several new ethanol plants are doing in the Texas Panhandle. Ethanol producers are replacing natural gas by taking manure from local feedlots and converting it to biogas for combined heat and electric power (CHP) to run the plant. This is efficient use of biogas, consumed onsite. Some municipal solid waste and dairy and livestock based biogas plants are either generating electric power for the grid or feeding cleaned biogas into natural gas pipelines. And yes these are good applications for converting biomass into biogas, especially from waste and byproducts.

Don T: “Of course corn stover ethanol does not make a lot of sense to address all of our needs.” Good Point. The above study’s use of “whole crop maize” (corn stover?) is not a good efficient feedstock for ethanol. You get 4 tons of corn stover per acre of corn. Normally, it is advantageously plowed under in preparation for the next crop. Experts say you should only remove no more than half the stover. This stuff is bulky and is a logistical nightmare to transport it to the refinery and store it and handle it, etc., which would also consume fossil fuels. It would be better to take 50% of the stover and convert it into biogas or pyrolysis bio crude in the middle of the field for the farmer’s onsite use. However, Poet Ethanol is adding cellulose ethanol capability to one production scale plant, where they will initially convert corn cobs to ethanol, and later supplement that with local biomass crops such as highly productive 10 ton switchgrass, 20 ton super sorghum, and 25 ton miscanthus. This will also enable them to replace natural gas with a portion of the biomass for production power, derived from synth gas. As to whether biomass burn, synth gas for production power, or biogas from biomass digestion is more efficient, that remains to be seen. Also depends on the process and the feedstock used.

Jim: I agree that biogas is efficient for specific applications, such as (1) sewage and landfill processing, (2) dairy, poultry and livestock manure processing, (3) and onsite biomass waste processing, where the feedstock is closeby, and (4) local biomass to CHP for ethanol production (and more). This is a thriving industry. But for the millions of vehicles we already have on the road, mass produced Liquid Fuels are the bomb. Biogas on the other hand is a bulky, much lower BTU gas that has infrastructure limitations and cost restraints setting up a used conventional vehicle to run on it. For me, I want a vehicle that I can fuel-up anywhere, but a biogas-methane-natural gas infrastructure is inadequate.

It does Not just boil down to what can be produced more efficiently. What’s more important is how biogas is best applied, and how ethanol is best applied. Also how biogas is managed and integrated, compared to how ethanol is managed and integrated. And the two don’t have to be separate. Biogas and ethanol can be advantageously integrated as noted above.

Regarding your comment about biomass being limited: Yes, if we use petroleum fuels to produce biomass, it’s limited. But we’re not locked into that. On waste land, algae is going to produce more biomass than we can possibly use. Algae can also be efficiently digested into biogas, if that’s what you want.

We can also use domestic biofuels to produce biofuels. More and more farmers are making their own biodiesel from their own oil crops. About 8% corn oil is being extracted from distillers grains and sold back to local farmers for biodiesel.

Check out the “Cyclone Green Revolution Engine”. This engine opens up a whole new world. It can run on any combustible fuel: Any combination of gaseous or liquid fuels, and notably, slurries of ultrasound fractionated oil rich algae, ethanol enhanced biomass and bio crude, even raw biogas and powdered biomass.

Fast growing algae, cattails, seaweed, invasive plants, and whatever else we can exploit, which can be grown locally in our waste water and graywater, are over 100 tons per acre per year. The success of biomass will also hinge on how we exploit our waste products into value added biomass, fuels, and energy. 4/5 of the planet is ocean. We are not limited.

With basic engine modifications, one part high octane ethanol can be diluted with two parts water, converted into a gaseous form onboard the vehicle, and still be an effective combustible fuel. This is what we need to do with our ethanol, as a transition fuel.


To who said I don't understand the challenge in using biomass for energy should do his research, I am perfectly aware that you need to remove the H2S from the biogas but it is still way simpler and cheaper than making cellulosic ethanol, cellulosic ethanol is one of the most challenging project ever developped by man and it is still unclear if it will work.

2nd the german who are pragmatic people came to teh conclusion that biogas was better than cellulosic ethanol from an efficiency point of view, and it is also cleaner once the H2S haas been removed.

So do your research before saying that people don't understand what you believe you understand but that you don't



There is millions of cars across the world that run on NG, they are way more efficient and cleaner that all thsi cars that you want to run on E85 where you are going to burn the ethanol with a poor efficiency because, the millions cars you are talking about are not designed to run on ethanol given the poor mileage of the american car fleet this is a shame to use ethanol, plus their emission will be worse. Ethanol can not be distributed by gazoline pipeline, so where is the conveniency that you are talking about ? Ethanol is certainly not the ideal fuel you are picturing,


Quoth Harvey D:

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?
Some of us have been saying this for years, and saying that CAFE regulations should have been replaced or assisted by fuel taxes since the 1980's.
There are no acceptable reasons why USA should have to import OIL, NG and Electricity after 2020.
The USA may have nobody willing to sell any of those things to it much earlier than that. :(

Quoth Roger Pham:

Extracting H2 and methane from waste biomass is the most efficient way to harness this renewable and storable source of energy.
Going to H2 is generally a waste of energy unless it is required for e.g. chemical synthesis.


And quoth Jeff Baker:

We are paying for an oil war sucking up $200 Billion a year and squandering 3% of our fuel supply....
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.
We're squandering a lot more than 3% with wasteful driving and idiotic "lifestyle" vehicles such as Hummers. We can fix both of them without a cent of subsidies, often at a large savings; "eco-driving" can save upwards of 20% at zero cost, and the "lifestyle" vehicles cost more than the efficient alternatives.
There are ... (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.
Do not forget that the value of each vehicle falls by about 20% when it is driven off the lot, and half the lifetime mileage is typically driven in the first 6 years (in the USA). We're going to replace those vehicles anyway, it's just a question of what the replacements will be like.
For example, Hydrous Ethanol: We can mix 4-5% water with ethanol and still blend it with gasoline.
No you can't. Any significant amount of water in ethanol separates it from gasoline, causing "emulsification". This has been a headache for decades.

Ford/MIT worked on a downsized dual-fuel engine a while back which used direct-injected ethanol to do charge cooling, allowing extreme turbocharging and a halving of engine displacement for the same peak output. The secondary fuel system would have run nicely with hydrous ethanol (cheaper) but this fuel would not mix with gasoline.

Ron Steenblik

Well said, Engineer-Poet!

"The USA may have nobody willing to sell any of those things to it much earlier than that. :( "

Only a fool underestimates the power of greed throughout the universe.

Jeff Baker

I am reporting that Brazil is running hydrous ethanol mixed with gasoline, and they have been for years. All regular gasoline in Brazil is blended with 24% ethanol, in solution with 4% water. If you blend the ethanol and the gasoline first and then add the water, it does Not work. The water must be bonded into the ethanol first, and then it blends freely with gasoline. The State of Louisiana is using 4% hydrous ethanol blended with gasoline in a pilot program with a company called Renergie. Preliminary tests conducted in Europe have proven that the use of hydrous ethanol, which eliminates the need for the hydrous-to-anhydrous dehydration processing step, results in an energy savings of between ten percent and forty-five percent during processing, a 4% product volume increase, higher mileage per gallon, a cleaner engine interior, and a reduction in greenhouse gas emissions. Dautzenberg and Netherlands-based client Process Design Center BV were investigating new ways to dry ethanol and stumbled across unexpected interactions among water, ethanol and gasoline. “We knew of the problems in drying ethanol,” he said, referring to the capital- and energy-intense employment of molecular sieves in dehydration. “We tried to find another way, so we asked ourselves, ‘Why not use gasoline to dry the ethanol?’ The hydrous ethanol and gasoline mix should not have been miscible, but it was fully miscible.” As a result, a ternary equilibrium diagram was formed. “We went to Shell in Holland with this information, and they said, ‘This cannot be true,’ but they investigated it further only to arrive at similar results,” Dautzenberg said. References: “Testing the Water” by Ron Kotrba; and “Ethanol Solution: Just Add Water” (Ethanol Producer Magazine).

What I advocate goes beyond 4% hydrous ethanol as described above: Taking ethanol to the next level, by modifying existing engines to run on 30% ethanol and 70% water (no gasoline). And I referenced above two researchers who accomplished that.

Ethanol and water as a fuel is nothing new. In the 1920's, the model A Ford cars and trucks ran on 165 proof ethanol: 17.5% water and 82.5% ethanol. ‘Makes you wonder why most cars on the road today are not allowed to do what a Model A could do 90 years ago. Time to change that.

Recently, a Pratt Community College engine testing team lead by instructor Greg Bacon, mixed 20% water with pure ethanol, and efficiency in the combustion chamber doubled. When the ethanol explodes, the water instantly turns into additional power in the form of steam and, can also provide hydrogen and oxygen inside the cylinder, under the right conditions.

Dongfeng, a major Chinese auto maker is introducing a car this year that runs on 65% ethanol and 35% water (no gasoline). This is a standard internal combustion engine equipped with a compact fuel processing device attached to the intake. They claim hydrogen is formed. Toyota also has a similar hydrous ethanol add-on prototype for a standard engine that produces on board hydrogen. Internal combustion engines can be highly efficient running on ethanol and water. A 50-50 blend of pure ethanol and water will ignite. But if more than 50% water is used in the blend, it will need to be heated and vaporized prior to combustion.

Jeff Baker


Prior to this response, I never referred to E85 or conveniency as you claim. Ethanol is still evolving. And I don’t suggest using E85, unless you have an engine that is optimized for it. The Saab 9-5 Biopower engine, which IS optimized for ethanol, outperforms gasoline, getting 20% more power, 16% greater torque, and 10% better mileage. The Lotus Exige 265E “Flexi” gets 45 more horse power on E85 than it gets on gasoline. Next year, Ford is introducing the EcoBoost gasoline engine, with an option for ethanol injection that will rival diesel power for a much lower cost. Within the next two years, Suzuki, Ford, GM and numerous other car makers will introduce engines which exploit the advantages of ethanol. Pure ethanol has higher octane, faster flame speed, lower emissions, lower burn temperature and less heat loss than gasoline. Major automakers are scheduled to produce smaller, lighter, high compression, turbocharged ethanol optimized engines, with high power to weight ratios, that are a lot more efficient than current gasoline and diesel engines. And the fuel will be cheaper, cleaner and made from domestic resources. Most importantly, ethanol mixes readily with water, a source of hydrogen and oxygen.

I’m not completely sold on combining ethanol with gasoline. Ethanol got in the fast lane, because we needed a replacement for MTBE, the oil industry oxidant for gasoline that was poluting our ground water. Aside from that, blending gasoline and ethanol is not neccesary. In the U.S., that was how politicians created an incentive for oil companies to distribute ethanol, by giving them a 51 cent per gallon tax credit to blend it with gasoline. Problem is, ethanol is more efficient when it’s mixed with water rather than gasoline.

Again, what I advocate is modifying existing engines to run on a blend of 30% pure ethanol and 70% water.

Kit P

“To who said I don't understand the challenge in using biomass for energy should do his research, I am perfectly aware that you need to remove the H2S from the biogas ..”

That was ENGINEERING challenge. Do you? Are you an engineer? No, you are not. H2S is not hard to remove but CO2 is a large component of biogas and hard to remove. The only easy and cheap way to remove CO2 from CH4 is too burn it an ICE or boiler. However, as the concentration of CO2 increases, the BTU content decreases and the mixture will not support combustion.

So Treehugger, if you know of an easy and cheap way of removing CO2 from biogas, let me and the rest of the world know.


There's a couple easy ways of removing CO2 from biogas. One is to simply let the gas 'settle' in a vertical tank. (CO2 is about 3 times denser than methane; 44 grams per mole versus 16 grams per mole).

The other is to bubble the biogas through water. Water readily dissolves CO2. There is an issue with regenerating the water, but one way of doing this is to grow algae in it; they can make quick use of dissolved CO2.

I'd say removing CO2 from biogas is much easier than separating ethanol from water; and less energy is needed.

There are other components in biogas, but they are predominantly CH4, CO2 and H2S.

solar nano

So Treehugger, if you know of an easy and cheap way of removing CO2 from biogas, let me and the rest of the world know.

Easy, easy answer!!! You use biogas to make electricity for an all electric society and recycle the CO2 into growing algae in a closed loop to make more fuel to generate electricty and so on and so on.........................!!!

solar nano

So Treehugger, if you know of an easy and cheap way of removing CO2 from biogas, let me and the rest of the world know.

Easy, easy answer!!! You use biogas to make electricity for an all electric society and recycle the CO2 into growing algae in a closed loop to make more fuel to generate electricity and so on and so on.........................!!!

Paul F. Dietz

There's a couple easy ways of removing CO2 from biogas. One is to simply let the gas 'settle' in a vertical tank. (CO2 is about 3 times denser than methane; 44 grams per mole versus 16 grams per mole).

Completely impractical. First, the tank would have to be on the order of a CO2 scale height in height to get a significant separation factor. In one gravity, this is several kilometers. Second, the time for the gas to come into this equilibrium would be the molecular diffusion time, which for a kilometers-tall tank would be outrageously long (centuries).

The only way this kind of separation could be even remotely feasible would be in a centrifuge, since the time required scales inversely as the square of the acceleration. Even then I doubt it would be competitive.


“this is several kilometers”

Ye of little imagination and low of out of the box thinking. Just put a few wind turbines and solar PV on the tower. Some of this is not new technology either. My Grandmother was always promoting different uses of space hooks.



If what you say was true, then radon would not collect in basements, and the Lake Nyos eruption would not have killed thousands of people with its CO2 plume (just like the dry ice mist you see on Halloween).

Further, methane and hydrogen leaks would not disperse harmlessly upward (which they do).

Since CO2 is denser than ambient air, methane should disperse upward even faster.

And then there's helium balloons.

I think you are discounting bouyancy in your calculations.


...and then there's the farmers that collect methane from cows in their barns - by collectors built in the roofs.



It happens that I am an enginer with some successfull achievement in his area. But anyway, compressing the biogas above 30 bars and cooling it to room temperature should liquefy the CO2 while the CH4 should be still in gazeous state so separating liquid from gaz shouldn't be that difficult my friend. Also if they can do membrane that can separate CO2 from N2 and O2 it should also worh for CO2 and CH4 though the CH4 might stick to the membrane because of the polarity of H in CH4.
Centrifugation should also be able to remove most of the CO2.

Paul F. Dietz

If what you say was true, then radon would not collect in basements, and the Lake Nyos eruption would not have killed thousands of people with its CO2 plume (just like the dry ice mist you see on Halloween).

You are wrong. Neither of the situations you describe there involve gases that are initially completely mixed, then separating under gravitational acceleration.

Paul F. Dietz

...and then there's the farmers that collect methane from cows in their barns - by collectors built in the roofs.

No, they don't. Where did you get this silly notion? Farmers collect methane/CO2 mixes produced in waste pits, collecting the gas from the pit without allowing it to be highly diluted by air.

Kit P

@ Treehugger

“So Treehugger, if you know of an easy and cheap way of removing CO2 from biogas, let me and the rest of the world know.”
Can I assume that you are a German engineer? I have a great deal respect for German engineering but let me explain the KISS principle. Keep It Simple Stupid.
What we have Treehugger is a failure to communicate. I need easy and cheap. I understand all the methods of gas separation Treehugger described, they are not easy or cheap.
Treehugger is making statement that are not universally true about biomass. It may be true in the EU. It is not true in the US. LCA must be adapted to each location.

In a location where large amounts of corn (or other biomass) is grown and large numbers of animals are fed the corn, then there is a large amount of manure and crop waste. This is an environmental issue in rural communities.

I can show a huge improvement by processing the waste using an common engineering solution called an anaerobic digesters (AD). AD are not generally an easy or cheap. Cooking with cow dung that dries in the barnyard is easier and cheaper than collecting it putting it in a simple AD to produce cooking gas. The huge sanitary improvement by processing animal waste justifies the increased cost.

So AD are used to treat waste. Biogas is a low BTU dirty byproduct gas. It almost universally flared or used as boiler feed. Biogas is a significant industrial safety hazard.

The debate here is akin to which is better for producing milk, cows or horses. As it turns out cows are much more efficient at converting the energy in grass than horses. Milk has lots of fat in it to supply humans with energy.
Being more efficient, can we assume Treehugger rides a cow to work? Why are the loons here never discussing EROI comparing cows, horses, NGV, and EVs.
Furthermore I know that dried woods has a high energy content. Why are those stupid farmers not feeding wood to cows and horses? Surly the teach EROI at AG colleges.
I get to work using an ICE POV. Ethanol, vegetable oil, animal fats have all been proven to useful fuels ICE fuels as have NG.

For all those who want to milk your horse and ride your cow to work based on the EROI, I hpoe you do not have an expectation many will follow.

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