Scientists at the University of Sheffield have shown how bacteria could be used as a future fuel. The research, published in the journal Bioinformatics, could have significant implications for the environment and the way we produce sustainable fuels in the future.

Like all living creatures, bacteria sustain themselves through their metabolism, a huge sequence of chemical reactions that transform nutrients into energy and waste.
Using mathematical computer models, the Sheffield team have mapped the metabolism of a type of bacteria called Nostoc. Nostoc fixes nitrogen and, in doing so, releases hydrogen that can then potentially be used as fuel. Fixing nitrogen is an energy intensive process and it wasn't entirely clear exactly how the bacterium produces the energy it needs in order to perform. Now the new computer system has been used to map out how this happens.
Until now, scientists have had difficulties identifying bacteria metabolic pathways. The bacterial metabolism is a huge network of chemical reactions, and even the most sophisticated techniques can only measure a small fraction of its activity.
Dr Guido Sanguinetti, from the University's Department of Computer Science, who led the study, said: "The research uncovered a previously unknown link between the energy machinery of the Nostoc bacterium and its core nitrogen metabolism. Further investigation of this pathway might lead to understanding and improvement of the hydrogen production mechanism of these bacteria. It will certainly be some time before a pool of bacteria powers your car, but this research is yet another small step towards sustainable fuels."
He added: " The next step for us will be further investigation into hydrogen production, as well as constructing more mathematical models capable of integrating various sources of biological data."
The Sheffield research is the result of an interdisciplinary collaboration of computer scientists and chemical engineers in a new discipline called Synthetic Biology. A major goal of Synthetic Biology is to understand which pathways of the bacterial metabolism are responsible for important functions, and then genetically engineer organisms that can perform the desired function more effectively.
The research, which was funded by the Engineering and Physical Sciences Research Council (EPSRC) and the Biomodular EU-FP6 project NEST, has been published in the journal Bioinformatics.

Aug 8, 2008
University of Sheffield

Genomics is accelerating improvements for converting plant biomass into biofuel—as an alternative to fossil fuel for the nation's transportation needs, reports Eddy Rubin, Director of the U.S. Department of Energy Joint Genome Institute (DOE JGI), in the journal Nature.

Rubin lays out a path forward for how emerging genomic technologies will contribute to a substantially different biofuels future as compared to the present corn-based ethanol industry—and in part mitigate the food-versus-fuel debate.
"The Apollo moon shot and the Human Genome Project rallied support for massive R&D efforts that created the capabilities to overcome obstacles that were not contemplated at the outset of these initiatives," says Rubin. "Similarly, today's barriers to improving biofuels are significant, but genetics and genomics can catalyze progress towards delivering, in the not-too-distant future, economically-viable and more socially acceptable biofuels based on lignocellulose."
While Rubin acknowledges that this strategy is in its infancy, rapid progress is being made.
"Over the past 10,000 years, wild plant species were selected for their desirable traits resulting in today's highly productive food crops. We simply don't have thousands of years in the face of the energy and climate challenges, so by applying the power of genomics to these problems, we are seeking to speed up the domestication of energy crops and the technologies for converting them to suitable biofuels as a more carbon-neutral approach to meeting part of our transportation needs."
In the Nature Review, Rubin describes the processes entailed in biofuel production from lignocellulose: the harvesting of biomass, pretreatment and saccharification, which results in the deconstruction of cell wall polymers into component sugars, and then the conversion of those sugars into biofuels through fermentation. Each step, he says, offers an opportunity for genomics to play a significant role.
"With the data that we are generating from plant genomes we can home in on relevant agronomic traits such as rapid growth, drought resistance, and pest tolerance, as well as those that define the basic building blocks of the plants cell wall—cellulose, hemicellulose and lignin. Biofuels researchers are able to take this information and design strategies to optimize the plants themselves as biofuels feedstocks—altering, for example, branching habit, stem thickness, and cell wall chemistry resulting in plants that are less rigid and more easily broken down."
For microbial biomass breakdown, Rubin says that many candidates have already been identified. These include Clostridia species for their ability to degrade cellulose, and fungi that express genes associated with the decomposition of the most recalcitrant features of the plant cell wall, lignin, the phenolic "glue" that imbues the plant with structural integrity and pest resistance. The white rot fungus Phanerochaete chrysosporium produces unique extracellular oxidative enzymes that effectively degrade lignin by gaining access through the protective matrix surrounding the cellulose microfibrils of plant cell walls.
Another fungus, the yeast Pichia stipitis, ferments the five-carbon "wood sugar" xylose abundant in hardwoods and agricultural harvest residue. Rubin says that Pichia's recently sequenced genome has revealed insights into the metabolic pathways responsible for this process, guiding efforts to optimize this capability in commercial production strains. Pathway engineering promises to produce a wider variety of organisms able to ferment the full repertoire of sugars derived from cellulose and hemicellulose and tolerate higher ethanol concentrations to optimize fuel yields.
Rubin also touches on the emerging technology of metagenomics—characterizing, without the need for laboratory culture, the metabolic profile of organisms residing in an environmental sample—for the identification of enzymes suitable for industrial-scale biofuel production.
"Using this prospecting technique, we can survey the vast microbial biodiversity to gain a better picture of the metabolic potential of genes and how they can be enlisted for the enzymatic deconstruction of biomass and subsequent conversion to high energy value fuels."
As an example, Rubin cites an analysis of the hindgut contents of nature's own bioreactor, the termite, (published in Nature (450, 560-565 [22 November 2007]), which has yielded more than 500 genes related to the enzymatic deconstruction of cellulose and hemicellulose.
The Nature Review goes on to list the feedstock genomes, microbial "biomass degraders," and "fuel producers" completed or in progress. These include the first tree genome completed—that of the poplar Populus trichocarpa and other plants in the sequencing queue, such as soybean, switchgrass, sorghum, eucalyptus, cassava, and foxtail millet. In addition, Rubin points to oil-producing algae as an alternative source for biodiesel production—with the alga Chlamydomonas reinhardtii, as just one of several algal species that has been characterized for their ability to efficiently capture and convert sunlight into energy.
"Given the daunting magnitude of fossil fuel used for transportation, we will likely have to draw from several different sources to make an appreciable impact with cellulosic biofuels, all of which will in some significant way will be informed by genomics," says Rubin.
"Toward this end, rapid new sequencing methods and the large-scale genomics previously applied to sequencing the human genome are being exploited by bioenergy researchers to design next-generation biofuels, higher-chain alcohols and alkanes, with higher energy content than petroleum and more adaptable to existing infrastructure."
The U.S. Department of Energy Joint Genome Institute, supported by the DOE Office of Science, unites the expertise of five national laboratories -- Lawrence Berkeley, Lawrence Livermore, Los Alamos, Oak Ridge, and Pacific Northwest -- along with the Stanford Human Genome Center to advance genomics in support of the DOE missions related to clean energy generation and environmental characterization and cleanup. DOE JGI's Walnut Creek, CA, Production Genomics Facility provides integrated high-throughput sequencing and computational analysis that enable systems-based scientific approaches to these challenges.

Journal reference:
Rubin et al. Genomics of cellulosic biofuels. Nature, 2008; 454 (7206): 841 DOI: 10.1038/nature07190


DOE/2008, August 14

[ 本帖最后由 longmarch10000 于 2008-8-14 18:18 编辑 ]

Scientists at Michigan State University have identified a new protein necessary for chloroplast development. The discovery could ultimately lead to plant varieties tailored specifically for biofuel production.

Chloroplasts, which are specialized compartments in plant cells, convert sunlight, carbon dioxide and water into sugars and oxygen ("fuel" for the plant) during photosynthesis. The newly discovered protein, trigalactosyldiacylglycerol 4, or TGD4, offers insight into how the process works.
"Nobody knew how this mechanism worked before we described this protein," said Christoph Benning, MSU professor of biochemistry and molecular biology. "This protein directly affects photosynthesis and how plants create biomass (stems, leaves and stalks) and oils."
Benning also is a member of the Great Lakes Bioenergy Research Center, a partnership between MSU and the University of Wisconsin-Madison funded by the U.S. Department of Energy to conduct basic research aimed at solving some of the most complex problems in converting natural materials to energy.
The research, published in the August 2008 issue of journal The Plant Cell, shows how TGD4 is essential for the plant to make chloroplasts. Plants that don't have the protein die before they can develop beyond the embryonic stage.
Understanding how TGD4 works may allow scientists to create plants that would be used exclusively to produce biofuels, possibly making the process more cost-effective. Most plants that are used to produce oils – corn, soybeans and canola, for example – accumulate the oil in their seeds.
"We've found that if the TGD4 protein is malfunctioning, the plant then accumulates oil in its leaves," Benning said. "If the plant is storing oil in its leaves, there could be more oil per plant, which could make production of biofuels such as biodiesel more efficient. More research is needed so we can completely understand the mechanism of operation."
Other members of the MSU research team are: Changcheng Xu, research assistant professor of biochemistry and molecular biology; Jilian Fan, research technician; and Adam Cornish, biochemistry undergraduate student at the time of the research and current graduate student.
The research was funded by the Energy Department and the National Science Foundation. Benning's research also is supported by the Michigan Agricultural Experiment Station.
For more information on MSU's biofuel and bioenergy research, visit: http://www.bioeconomy.msu.edu.


Corn and soybean crops on the MSU campus. (Credit: Photo by Kurt Stepnitz)

Aug 15, 2008
Michigan State University

[ 本帖最后由 longmarch10000 于 2008-8-16 11:53 编辑 ]

In the world of alternative fuels, there may be nothing greener than pond scum.

Algae are tiny biological factories that use photosynthesis to transform carbon dioxide and sunlight into energy so efficiently that they can double their weight several times a day.
As part of the photosynthesis process algae produce oil and can generate 15 times more oil per acre than other plants used for biofuels, such as corn and switchgrass. Algae can grow in salt water, freshwater or even contaminated water, at sea or in ponds, and on land not suitable for food production.
On top of those advantages, algae — at least in theory — should grow even better when fed extra carbon dioxide (the main greenhouse gas) and organic material like sewage. If so, algae could produce biofuel while cleaning up other problems.
"We have to prove these two things to show that we really are getting a free lunch," said Lisa Colosi, a professor of civil and environmental engineering who is part of an interdisciplinary University of Virginia research team, recently funded by a new U.Va. Collaborative Sustainable Energy Seed Grant worth about $30,000.
With the grant, the team will try to determine exactly how promising algae biofuel production can be by tweaking the inputs of carbon dioxide and organic matter to increase algae oil yields.
Scientific interest in producing fuel from algae has been around since the 1950s, Colosi said. The U.S. Department of Energy did pioneering research on it from 1978 to 1996. Most previous and current research on algae biofuel, she said, has used the algae in a manner similar to its natural state — essentially letting it grow in water with just the naturally occurring inputs of atmospheric carbon dioxide and sunlight. This approach results in a rather low yield of oil — about 1 percent by weight of the algae.
The U.Va. team hypothesizes that feeding the algae more carbon dioxide and organic material could boost the oil yield to as much as 40 percent by weight, Colosi said.
Proving that the algae can thrive with increased inputs of either carbon dioxide or untreated sewage solids will confirm its industrial ecology possibilities — to help with wastewater treatment, where dealing with solids is one of the most expensive challenges, or to reduce emissions of carbon dioxide, such as coal power-plant flue gas, which contains about 10 to 30 times as much carbon dioxide as normal air.
"The main principle of industrial ecology is to try and use our waste products to produce something of value," Colosi said.
Research partner Mark White, a professor at the McIntire School of Commerce, will help the team quantify the big-picture environmental and economic benefits of algae biofuel compared to soy-based biodiesel, under three different sets of assumptions.
White will examine the economic benefits of algae fuel if the nation instituted a carbon cap-and-trade system, which would increase the monetary value of algae's ability to dispose of carbon dioxide. He will also consider how algae fuel economics would be impacted if there were increased nitrogen regulations (since algae can also remove nitrogen from air or water), or if oil prices rise to a prohibitive level.
The third team member is Andres Clarens, a professor of civil and environmental engineering with expertise in separating the oil produced by the algae.
The team will experiment on a very small scale — a few liters of algae at a time. They will seek to optimize the oil output by using a pragmatic engineering approach, testing basic issues like whether it makes a difference to grind up the organic material before feeding it to the algae.
Wastewater solids and algae, either dead or alive, are on the menu. "We're looking at dumping the whole dinner on top of them and seeing what happens," Colosi said.
Some of these pragmatic issues may have been tackled already by the various private companies, including oil industry giants Chevron and Shell, which are already researching algae fuel, but a published scientific report on these fundamentals will be a major benefit to other researchers looking into algae biofuel.
Published evidence of improved algae oil output might spur significant follow-up efforts by public and private sectors, since the fundamentals of this technology are so appealing, Colosi said. Research successes would also open the door to larger grants from agencies like the U.S. Department of Energy, and could be immediately applicable to the handful of pilot-scale algae biofuel facilities recently funded by Shell and start-up firms.


Environmental engineering professors Andres Clarens (center) and Lisa Colosi (right) have teamed up with commerce professor Mark White to investigate how algae may offer the biofuel of the future. (Credit: Melissa Maki)

Aug 15, 2008
University of Virginia

With oil prices skyrocketing, the search is on for efficient and sustainable biofuels. Research published this month in Agronomy Journal examines one biofuel crop contender: corn stover.

Corn stover is made up of the leaves and stalks of corn plants that are left in the field after harvesting the edible corn grain. Corn stover could supply as much as 25% of the biofuel crop needed by 2030.
Scientists with the USDA-ARS Agroecosystem Unit located at the University of Nebraska examined the long-term sustainability of using corn stover as a biofuel crop.
When corn stover is not harvested as a biofuel crop, it can be left on the fields to restore vital nutrients to the soil. Full-scale harvesting of corn stover may deplete the soil.
Researchers measured the soil organic carbon levels and residue production over 14 years in fields planted continuously with corn, continuously with soybeans, and with a rotation of corn and soybeans. Organic carbon rates were found to stay steady or even increase in all three field types.
Gary Varvel and Wally Wilhelm, who conducted the study, said "These results suggest that a portion of corn stover could be harvested for biofuel production without reducing soil organic carbon levels in high yielding systems. However, since this study did not study the direct impact of stover removal, that aspect remains to be evaluated."
Research into the effects of residue removal on soil organic carbon levels in several different cropping systems is ongoing at this and several other USDA-ARS locations throughout the U.S. Much of this research is under the auspices of a multi-location CRIS project within ARS called REAP (Renewable Energy Assessment Project).
Journal reference:
G. E. Varvel and W. W. Wilhelm. Soil Carbon Levels in Irrigated Western Corn Belt Rotations. Agronomy Journal, 2008; 100 (4): 1180 DOI: 10.2134/agronj2007.0383

Aug 20, 2008
American Society of Agronomy

[ 本帖最后由 longmarch10000 于 2008-8-20 12:58 编辑 ]

Researchers here have found a way to convert ethanol and other biofuels into hydrogen very efficiently.

A new catalyst makes hydrogen from ethanol with 90 percent yield, at a workable temperature, and using inexpensive ingredients.
Umit Ozkan, professor of chemical and biomolecular engineering at Ohio State University, said that the new catalyst is much less expensive than others being developed around the world, because it does not contain precious metals, such as platinum or rhodium.
"Rhodium is used most often for this kind of catalyst, and it costs around $9,000 an ounce," Ozkan said. "Our catalyst costs around $9 a kilogram."
She and her co-workers presented the research Wednesday, August 20 at the American Chemical Society meeting in Philadelphia.
The Ohio State catalyst could help make the use of hydrogen-powered cars more practical in the future, she said.
"There are many practical issues that need to be resolved before we can use hydrogen as fuel -- how to make it, how to transport it, how to create the infrastructure for people to fill their cars with it," Ozkan explained.
"Our research lends itself to what's called a 'distributed production' strategy. Instead of making hydrogen from biofuel at a centralized facility and transporting it to gas stations, we could use our catalyst inside reactors that are actually located at the gas stations. So we wouldn't have to transport or store the hydrogen -- we could store the biofuel, and make hydrogen on the spot."
The catalyst is inexpensive to make and to use compared to others under investigation worldwide. Those others are often made from precious metals, or only work at very high temperatures.
"Precious metals have high catalytic activity and -- in most cases -- high stability, but they're also very expensive. So our goal from the outset was to come up with a precious-metal-free catalyst, one that was based on metals that are readily available and inexpensive, but still highly active and stable. So that sets us apart from most of the other groups in the world."
The new dark gray powder is made from tiny granules of cerium oxide -- a common ingredient in ceramics -- and calcium, covered with even smaller particles of cobalt. It produces hydrogen with 90 percent efficiency at 660 degrees Fahrenheit (around 350 degrees Celsius) -- a low temperature by industrial standards.
"Whenever a process works at a lower temperature, that brings energy savings and cost savings," Ozkan said. “Also, if the catalyst is highly active and can achieve high hydrogen yields, we don’t need as much of it. That will bring down the size of the reactor, and its cost”.
The process starts with a liquid biofuel such as ethanol, which is heated and pumped into a reactor, where the catalyst spurs a series of chemical reactions that ultimately convert the liquid to a hydrogen-rich gas.
One of the biggest challenges the researchers faced was how to prevent "coking" -- the formation of carbon fragments on the surface of the catalyst. The combination of metals -- cerium oxide and calcium -- solved that problem, because it promoted the movement of oxygen ions inside the catalyst. When exposed to enough oxygen, the carbon, like the biofuel, is converted into a gas and gets oxidized; it becomes carbon dioxide.
At the end of the process, waste gases such as carbon monoxide, carbon dioxide and methane are removed, and the hydrogen is purified. To make the process more energy-efficient, heat exchangers capture waste heat and put that energy back into the reactor.  Methane recovered in the process can be used to supply part of the energy.
Though this work was based on converting ethanol, Ozkan's team is now studying how to use the same catalyst with other liquid biofuels. Her coauthors on this presentation included Ohio State doctoral students Hua Song and Lingzhi Zhang.
This research was funded by the Department of Energy.

Aug 20, 2008
Ohio State University

So perfect!

A new Fischer-Tropsch catalyst could offer the potential for agricultural waste to be turned into biofuel at small local plants, avoiding high transport costs to large waste collection centres. The cobalt hydride catalyst, developed by Oxford Catalysts, UK, is designed for use in small-scale Fischer-Tropsch (FT) microchannel reactors, which convert syngas - carbon monoxide and hydrogen - into biofuel.
Second generation biofuel production is seen as a sustainable alternative to growing fuel crops, but has the drawback that it takes one tonne of waste to produce one barrel of liquid fuel, explains Derek Atkinson, business development director, Oxford Catalysts. This means that biomass plants can't compete for scale with gas-to-liquid plants such as Shell's FT plant in Qatar, which produces 140 000 tonnes of liquid fuel per day from natural gas.
'To make biomass-to-liquid conversion more attractive needs more active and process intensified technology,' he adds. Microchannel reactors could be the answer - their millimetre-wide channels rapidly dissipate the large amounts of heat produced by the FT reaction so that very active catalysts can be used.
New kind of reactor
'The microchannel reactor is a new kind of reactor never applied before in industry,' says Giuseppe Bellussi, a catalysis expert at Italian energy firm Eni. 'In principle it should allow a better heat transfer and catalyst efficiency, because of the small particle size. But the fluid dynamics could be unfavourable, including through partial pore blocking.' Bulk carbide catalysts have never before been used in industry, adds Bellussi.
The new FT catalyst is manufactured using Oxford Catalyst's patented organic matrix combustion (OMX) technology, which the company claims gives high metal loadings and small catalyst crystal sizes. OMX combines the metal salt with an organic component to make a complex that stabilises the metal. The complex is heated to high temperatures until combustion takes over and fixes the very small crystals. The heating stage is so rapid that the metal crystallites do not have time to grow.
Oxford Catalysts has tested the catalyst's performance over a period of months, but doesn't yet know its ultimate lifetime. 'Performance dropped only slightly in our tests - a decay of fractions of one per cent,' reveals Atkinson. Replacing catalysts in the microchannel reactors would be extremely expensive.
Oxford Catalysts has signed a memorandum of understanding with a company that develops FT microchannel reactors to use the new catalyst in small-scale FT applications, including the conversion of biowaste into liquid fuel. It is also working with a catalyst manufacturer to scale up production.
Oxford Catalysts is also looking to broaden the appeal of FT and has a concept for an integrated approach to treating municipal solid waste, which links together waste treatment processes and incorporates a small-scale FT plant. The company is trying to build a consortium to work on its concept and is seeking EU funding.
Emma Davies



Aug 22, 2008
Chemistry World

AMES, Iowa, August 20, 2008 (ENS) - A method of making potentially cheap ethanol fuel out of garbage and other waste materials by deploying a combination of modern and old technologies is under development by government and university researchers.
The process involves the use of nanotechnology and gasification to convert carbon-based materials into a product called synthesis gas, or syngas, which in turn can be made into ethanol.
Developing new ways of producing biofuels such as ethanol is urgent business as the country and world scout for alternatives to fossil fuels.
For now, ethanol is made chiefly by fermenting corn, diverting the valuable commodity from serving as food for people and livestock.
"The great thing about using syngas to produce ethanol is that it expands the kinds of materials that can be converted into fuels," said Victor Lin, director of the Chemical and Biological Science Program at the U.S. Department of Energy's Ames Laboratory."
"You can use the waste product from the distilling process or any number of other sources of biomass, such as switchgrass or wood pulp," Lin said in a statement.
"Basically any carbon-based material can be converted into syngas," he said. "And once we have syngas, we can turn that into ethanol."
Ames scientists, working with colleagues at Iowa State University, are employing gasification to make syngas.
To make the gas, they subject carbon-based feedstocks to high temperature and pressure in an oxygen-controlled atmosphere.

North Dakota Gasification Great Plains Synfuels Plant

Syngas is composed mainly of carbon monoxide and hydrogen, along with a smaller amount of carbon dioxide and methane, according to the lab.
Gasification is not a new technology but has been around since the 1800s, when it was used to extract gas from coal to produce fuel for lighting and cooking.
The attempt to turn syngas into ethanol also is not new. Scientists have been researching the process for 90 years, according to a study published in January in "Energy & Fuels," a journal of the American Chemical Society.
"There was some interest in converting syngas into ethanol during the first oil crisis back in the ?0s," Lin said, but there was a problem. "They could produce ethanol, but you'd also get methane, aldehydes and a number of other undesirable products."
The fault lay with the catalysts, materials that promote and speed chemical reactions without themselves being changed.
Lin and his colleagues hit upon using as catalysts invisibly small nanoparticles of a metal alloy.
The nanoscale is almost inconceivably small. A nanometer - one billionth of a meter - is about the size of 10 hydrogen or five silicon atoms, and the width of a human hair is about 80,000 nanometers.
Ames Laboratory describes the catalyst nanoscale particles as having thousands of channels running through them, which increases the amount of catalytic surface area 100-fold over ordinary-sized catalysts.
"If we can increase the amount of surface area for the catalyst, we can increase the amount of ethanol produced," Lin explained.
While nanotechnology offers a solution to the catalyst problem, gasification is another technology that is required to produce ethanol from garbage.
Private industry is chasing the syngas-to-ethanol goal, as well, and employing gasification to do it.
The company Coskata Inc., in partnership with General Motors, is building a $25 million demonstration plant near Pittsburgh, Pennsylvania, where it plans to make ethanol from woody biomass, and farm and industrial wastes.
The company's goal is to produce ethanol from non-food-based sources for less than $1 a gallon.
On its website, Coskata says the company uses a combination of gasification and fermentation to convert carbon-based wastes into syngas, and then into ethanol.
The pilot plant is designed to produce 40,000 gallons of fuel a year. The company said it plans to complete a full-size plant capable of producing 50 million to 100 million gallons of fuel a year by 2011.
To control the chemical makeup of the syngas for reliable operation and high-quality, researchers at the Center for Sustainable Environmental Technologies, or CSET, at Iowa State have developed fluidized bed gasifiers. The gas produced can be used in a range of applications from replacing natural gas in grain ethanol plants to providing hydrogen for fuel cells.
CSET director Robert Brown says, "Gasification to ethanol has received increasing attention as an attractive approach to reaching the federal Renewable Fuel Standard of 36 billion gallons of biofuel."
Authorized by the Energy Policy Act of 2005, the federal Renewable Fuels Standard calls for the production of 36 billion gallons of biofuels annually by 2022.
Of this, roughly 16 billion gallons is expected to be from cellulosic biofuels, derived from woody biomass - plant sources such as trees and grasses.

[ 本帖最后由 longmarch10000 于 2008-8-23 10:16 编辑 ]

In experiments, sweet potatoes grown in Maryland and Alabama yielded two to three times as much carbohydrate for fuel ethanol production as field corn grown in those states, Agricultural Research Service (ARS) scientists report. The same was true of tropical cassava in Alabama.

The sweet potato carbohydrate yields approached the lower limits of those produced by sugarcane, the highest-yielding ethanol crop. Another advantage for sweet potatoes and cassava is that they require much less fertilizer and pesticide than corn.
Lew Ziska, a plant physiologist at the ARS Crop Systems and Global Change Laboratory in Beltsville, Md., and colleagues at Beltsville and at the ARS National Soil Dynamics Laboratory in Auburn, Ala., performed the study. The research is unique in comparing the root crops to corn, and in growing all three crops simultaneously in two different regions of the country.
The tests of corn, cassava and sweet potato were in the field at Beltsville, and in large soil bins at Auburn.
For the sweet potatoes, carbohydrate production was 4.2 tons an acre in Alabama and 5.7 tons an acre in Maryland. Carbohydrate production for cassava in Alabama was 4.4 tons an acre, compared to 1.2 tons an acre in Maryland. For corn, carbohydrate production was 1.5 tons an acre in Alabama and 2.5 tons an acre in Maryland.
The disadvantages to cassava and sweet potato are higher start-up costs, particularly because of increased labor at planting and harvesting times. If economical harvesting and processing techniques could be developed, the data suggests that sweet potato in Maryland and sweet potato and cassava in Alabama have greater potential than corn as ethanol sources.
Further studies are needed to get data on inputs of fertilizer, water, pesticides and estimates of energy efficiency. Overall, the data indicate it would be worthwhile to start pilot programs to study growing cassava and sweet potato for ethanol, especially on marginal lands.
The additional research could help develop new biofuel sources without diverting field corn supplies from food and feed use to fuel.

Sweet potatoes can yield two to three times as much fuel ethanol as field corn, approaching the amount that sugarcane can produce. (Credit: Photo courtesy of the Louisiana Sweet Potato Commission)


Aug 25, 2008
USDA/Agricultural Research Service