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LIFECYCLE ANALYSIS: Using plants to produce electricity rather than ethanol results in more energy from the same amount of land.
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Image: Courtesy of McDade and Campbell / UC Merced
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The environmental case for ethanol from corn continues to weaken. Turning the food crop into ethanol would not be the best use of the energy embedded in the kernels' carbohydrates, according to a new study in Science. That's because fermenting corn into ethanol delivers less liquid fuel energy for internal combustion engines than does burning the kernels to generate power for electric motors.
"We had been studying the area of land that would be available to grow crops for energy and we were curious to discover the most efficient use of these crops," explains environmental engineer Elliott Campbell of the University of California, Merced, who led the study. "We found that with a given amount of biomass you could produce more transportation and greenhouse gas offsets with electricity than with ethanol."
The new study shows that burning biomass to produce electricity rather than converting it to ethanol (made from corn kernels or the other parts of the plant, so-called cellulosic ethanol) delivers 81 percent more miles per acre of transportation in electric vehicles than ethanol burned in internal combustion, even taking into account the lifetime costs of the expensive batteries available today. "The input energy to produce an electric vehicle was 1.5 times the energy to produce an [internal combustion vehicle]," Campbell says. "The batteries currently require large energy inputs in the vehicle production component of our life cycle assessment."
On average, looking at a wide variety of source crops (corn kernels to switchgrass), ways to convert plants to energy, and vehicle sizes (ranging from compact cars to SUVs), bioelectricity delivered 56 percent more energy for transportation per acre, even including the fact that making ethanol produces other useful products, such as cattle feed. To take just one example: a small truck powered by bioelectricity could travel almost 15,000 city and highway miles (24,000 kilometers) compared with just 8,000 comparable miles (13,000 kilometers) for an internal combustion equivalent.
From the atmosphere's point of view, growing biomass to burn in a power plant and using the electricity to move a car avoids 10 tons of carbon dioxide emissions per acre, or 108 percent more emission offsets than ethanol. "One other aspect of the electricity pathway is that most emissions are concentrated in one location, which provides perhaps an opportunity for more control of the emissions," Campbell notes. "It also perhaps locates [other air pollution] emissions in a place where impacts might not be as harmful as where cars are driven today."
Of course, such a bioelectricity future for transportation would also rely on widespread availability of cars and trucks with batteries and electric motors. "A great deal of innovation must happen in vehicle and power transmission technologies to make that a reality," argues Renewable Fuels Association spokesman Matt Hartwig, an ethanol trade association that owns an ethanol-electric hybrid car. "In the meantime, Americans still need liquid transportation fuels. If the goal is to have more of those gallons come from renewable sources rather than imported oil, fuels like ethanol are the only technologies that are having an impact today."
He adds: "In theory, you could have a plug-in hybrid with a renewable fuel powered [internal combustion engine] and eliminate the need for petroleum all together."
The Obama administration seems to agree, granting $786 million in 2009 for biofuels research and setting up the Biofuels Interagency Working Group to study how best to meet the renewable fuel standard mandated by Congress that will require increasing the amount of renewable fuels, such as ethanol, to 36 billion gallons by 2022.
But the U.S. Environmental Protection Agency (and the California Air Resources Board) have noted that turning corn into ethanol can actually be a significant source of greenhouse gas emissions and other unintended environmental effects, largely by driving the expansion of agriculture and its attendant pollution—as evidenced by previous studies published in Science.
All use of biomass—whether for ethanol or electricity—runs the risk of displacing food crops, however, as well as the need for large amounts of water. "Both pathways could be totally disastrous if these types of impacts can't be avoided," Campbell admits. "This is going to be a constrained area of land and amount of biomass, so how much transportation and greenhouse gas offsets can we milk out of this constrained land? It looks like the electricity pathway might get us more bang for the buck."
And burning biomass for electricity while capturing the CO2 emissions from such a power plant can actually result in carbon-negative power generation—taking CO2 out of the atmosphere. "By sequestering the flue gas CO2 at the power plant, the bioelectricity pathway could result in a net removal of CO2 from the air," the researchers wrote, and that could help with the problem of ever-rising levels of the greenhouse gases causing climate change.
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24 Comments
Add CommentA century ago engineers were pursuing technically sweet projects with no concern about violating the First Law of Thermo (prepetual motion, for example).
Reply | Report Abuse | Link to thisToday, they are attempting to beat the Second Law (entropy) via similar schemes (electric cars, etc).
Indeed, these seem to be the projects most touted by Sci Amno doubt catering to a readership rather than science.
I recently read an article that said the a means of turning CO2 into Methane had been discovered. If true this would be much better than storing the CO2 in holes in the earth (salt mines, etc.) and acturally create more cleaner energy.
Reply | Report Abuse | Link to thisCarbon dioxide and other greenhouse gasses contribute to climate change, which has been ongoing since our planet's birth. They are not the primary cause of rapid climate change. Human populations and activities are to blame.
Reply | Report Abuse | Link to thisAgriculture in the primary activity that has brought on the sixth extinction. By eradicating 25% of forests we have reduced 25% of primary food production from photosynthesis. The energy that would have been used to generate basic food is now heating our environment. As a consequence of lower food production populations of animals other than man have been decimated. Man's population boom has been at the expense of the other species.
Our planet also evolved and reached its current state as a result of life on the planet shaping its ongoing development. Biodiversity nullified the impacts of species specific degradation of the liveable environment. Loss of forests and biodiversity will end human life on this planet in the not to distant future. Like hive intelligence, life intelligence will eliminate that which threatens its future.
This planet cannot comfortably support 1 billion people, never mind the 6 billion and climbing we see now.
Reply | Report Abuse | Link to thisAs it stands now suburban and and urban people live lives akin to that of hens in industrial factory farms... and exhibit the same diminution of their spirits and intelligence.
Looking for ways to warehouse ever more people is a fool's errand that has already bankrupted the planet.
We see an endless supply of people who have been reduced to being pets held in common by society. Both suburbia and the "project people" are examples of the indoor and outdoor pets we collectively keep.
@e_caroline,
Reply | Report Abuse | Link to thisRespectfully submitted that you lead by example and promptly off your self to save the planet.
From a CO2 budget perspective, you don't have to convert biomass to fuel. Just grow the fastest-growing plants you can, then bury the plants with the embedded carbon deeply in the ground. As long as you bury as much carbon as you remove and burn in the form of ancient hydrocarbons, the net effect on the CO2 budget is zero.
Reply | Report Abuse | Link to thisOf course, it would be nice to build reliable energy generation facilities that don't depend on the limited supply of hydrocarbon. Too bad Obama doesn't understand the necessity of nuclear power, only political power.
We can see at least one example of the diminished intellect that results from a diminished life.
Reply | Report Abuse | Link to thisWhen grains are converted to ethanol most of the food value remains and is used as animal feed and in fact it is a better quality livestock feed then the original grain.
Reply | Report Abuse | Link to thisWhen it is combusted for electric power it is totally used up.
Many other "facts" in this article are equally made up of half truths, There is one fact that is real, using grains for fuel is stupid.
I've been a farmer for over 50 years and have studied biofuels since the 1970's and am an electrical engineer,so I have a little personal knowlage in this field.
Biomass can be the fuel to power steam locomotives. The smoke can be minimized by efficient combustion and electrostatic scrubbers.
Reply | Report Abuse | Link to thisBiomass can be the fuel to power steam locomotives. The smoke can be minimized by efficient combustion and electrostatic scrubbers.
Reply | Report Abuse | Link to thisCorn seems to be one of the least efficient energy crops. Has anyone investigated the role that patents play in our ongoing determination to make corn a viable option? Monsanto and ADM seem to be the main beneficiaries in this scheme.
Reply | Report Abuse | Link to thisAnd what ever happened to methanol? It seems that making methanol from biomass and converting it to gasoline using the decades old patented process developed by Exxon-Mobil & Georgia Tech might be a worthwhile endeavor.
Competent energy discussions begin with entropy. No entropy analysis; no credibility.
Reply | Report Abuse | Link to thisThe best way to convert plants to energy?
Reply | Report Abuse | Link to thisEat them.
I have posted my comments here ...
Reply | Report Abuse | Link to thishttp://joydip.blogspot.com/2008/10/bio-fuel-critique.html
Joydip.
Drill...
Reply | Report Abuse | Link to thisDrill, drill, drill. Use the profits to fund "Green Tech." (somewhere around 2.7 trillion over 10 years)
Reply | Report Abuse | Link to this6 billion people, you think that now they're getting a taste of "Western Civilization," your arrogant butt can put them back on their bicycles, hugh?
It is even harder for the average ape to believe that he has descended from man.
You won't end racism, till the races breed each other out.
And you can't save the planet one country at a time. Everybody's got to get in the pool.
The most efficient biomass conversion method is to convert it into Biochar, releasing plenty of hydrogen. See www.eprida.com for updates on the latest technology. The Biochar can be used as a fertiliser, and the hydrogen used for fuel. Cheap and simple, and can even be applied by third world farmers to earn carbon credits...
Reply | Report Abuse | Link to thisThe best way to turn plants into energy is to eat them. Why is biofuel being considered? Just because we can turn food into biofuel, it doesn't mean we should.
Reply | Report Abuse | Link to thisYes, I agree. The best approach to "bioenergy" is to forget about it and use other approaches that make better sense.
Reply | Report Abuse | Link to thisam
Allen Muller : What other approaches that make better sense?
Reply | Report Abuse | Link to thisIf you are looking for electricity to operate transport, generating it directly via PV, or solar thermal, or wind, is likely to be far cleaner and more effective than burning plants.
Reply | Report Abuse | Link to thisAlan Muller : Pyrolysing biomass is perfectly clean and requires no other energy source. It also has the advantage that it captures and stores atmospheric CO2 in the form of charcoal. It is not a competitor to other forms of electricity generation but a complement. See www.eprida.com for a full explanation.
Reply | Report Abuse | Link to thisI looked at the Aprida site. It's just one of dozens promoting this sort of thing. "Pyrolizing biomass" is obviously not "perfectly clean."
Reply | Report Abuse | Link to thisAlan : Please read the eprida site technical reports more carefully. You will find that the researchers have done hundreds of tests to define the parameters which affect biochar manufacture, and fully master the subject, which has been under study for more than ten years. A full comprehension of bio-geo-chemistry is required to follow the explanations, but with a little patience you should grasp the essentials.
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