Sweet diesel! Discovery resurrects process to convert sugar directly to diesel
Published: Wednesday, November 7, 2012 - 14:37 in Physics & Chemistry
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Robert Sanders photo.
While the fuel's cost is still higher than diesel or gasoline made from fossil fuels, the scientists said the process would drastically reduce greenhouse gas emissions from transportation, one of the major contributors to global climate change.
"What I am really excited about is that this is a fundamentally different way of taking feedstocks -- sugar or starch -- and making all sorts of renewable things, from fuels to commodity chemicals like plastics," said Dean Toste, UC Berkeley professor of chemistry and co-author of a report on the new development that will appear in the Nov. 8 issue of the journal Nature.
The work by Toste, coauthors Harvey Blanch and Douglas Clark, UC Berkeley professors of chemical and biomolecular engineering, and their colleagues was supported by the Energy Biosciences Institute, a collaboration between UC Berkeley, Lawrence Berkeley National Laboratory and the University of Illinois at Urbana Champaign, and funded by the energy firm BP.
The linkage between Toste, whose EBI work is in the development of novel catalysts, and Clark and Branch, who are working on cellulose hydrolysis and fermentation, was first suggested by BP chemical engineer Paul Willems, EBI associate director. The collaboration, Willems said, illustrates the potential value that can come from academic-industry partnerships like the EBI.
The late Weizmann's process employs the bacterium Clostridium acetobutylicum to ferment sugars into acetone, butanol and ethanol. Blanch and Clark developed a way of extracting the acetone and butanol from the fermentation mixture while leaving most of the ethanol behind, while Toste developed a catalyst that converted this ideally-proportioned brew into a mix of long-chain hydrocarbons that resembles the combination of hydrocarbons in diesel fuel.
Tests showed that it burned about as well as normal petroleum-based diesel fuel.
"It looks very compatible with diesel, and can be blended like diesel to suit summer or winter driving conditions in different states," said Blanch.
The process is versatile enough to use a broad range of renewable starting materials, from corn sugar (glucose) and cane sugar (sucrose) to starch, and would work with non-food feedstocks such as grass, trees or field waste in cellulosic processes.
"You can tune the size of your hydrocarbons based on the reaction conditions to produce the lighter hydrocarbons typical of gasoline, or the longer-chain hydrocarbons in diesel, or the branched chain hydrocarbons in jet fuel," Toste said.
The fermentation process, dubbed ABE for the three chemicals produced, was discovered by Weizmann around the start of World War I in 1914, and allowed Britain to produce acetone, which was needed to manufacture cordite, used at that time as a military propellant to replace gunpowder. The increased availability and decreased cost of petroleum soon made the process economically uncompetitive, though it was used again as a starting material for synthetic rubber during World War II. The last U.S. factory using the process to produce acetone and butanol closed in 1965.
Nevertheless, Blanch said, the process by which the Clostridium bacteria convert sugar or starch to these three chemicals is very efficient. This led him and his laboratory to investigate ways of separating the fermentation products that would use less energy than the common method of distillation.
They discovered that several organic solvents, in particular glyceryl tributyrate (tributyrin), could extract the acetone and butanol from the fermentation broth while not extracting much ethanol. Tributyrin is not toxic to the bacterium and, like oil and water, doesn't mix with the broth.
Brought together by the EBI, Blanch and Clark found that Toste had discovered a catalytic process that preferred exactly that proportion of acetone, butanol and ethanol to produce a range of hydrocarbons, primarily ketones, which burn similarly to the alkanes found in diesel.
"The extractive fermentation process uses less than 10 percent of the energy of a conventional distillation to get the butanol and acetone out -- that is the big energy savings," said Blanch. "And the products go straight into the chemistry in the right ratios, it turns out."
The current catalytic process uses palladium and potassium phosphate, but further research is turning up other catalysts that are as effective, but cheaper and longer-lasting, Toste said. The catalysts work by binding ethanol and butanol and converting them to aldehydes, which react with acetone to add more carbon atoms, producing longer hydrocarbons.
"To make this work, we had to have the biochemical engineers working hand in hand with the chemists, which means that to develop the process, we had learn each other's language," Clark said. "You don't find that in very many places."
Clark noted that diesel produced via this process could initially supply niche markets, such as the military, but that renewable fuel standards in states such as California will eventually make biologically produced diesel financially viable, especially for trucks, trains and other vehicles that need more power than battery alternatives can provide.
"Diesel could put Clostridium back in business, helping us to reduce global warming," Clark said. "That is one of the main drivers behind this research."
http://newscenter.berkeley.edu/2012/11/07/discovery-resurrects-process-to-convert-sugar-directly-to-diesel/
Sweet diesel! Discovery resurrects process to convert sugar directly to diesel
BERKELEY —
A long-abandoned fermentation process once used to turn starch into explosives can be used to produce renewable diesel fuel to replace the fossil fuels now used in transportation, UC Berkeley scientists have discovered.
Graduate student Zachary Baer works with a fermentation chamber in the Energy Biosciences Building to separate acetone and butanol (clear top layer) from the yellowish Clostridium brew at the bottom. The chemicals can be extracted and catalytically altered to make a fuel that burns like diesel. Robert Sanders photo.
Campus chemists and chemical engineers teamed up to produce diesel fuel from the products of a bacterial fermentation discovered nearly 100 years ago by the first president of Israel, chemist Chaim Weizmann. The retooled process produces a mix of products that contain more energy per gallon than ethanol that is used today in transportation fuels and could be commercialized within 5-10 years.
While the fuel’s cost is still higher than diesel or gasoline made from fossil fuels, the scientists said the process would drastically reduce greenhouse gas emissions from transportation, one of the major contributors to global climate change.
“What I am really excited about is that this is a fundamentally different way of taking feedstocks – sugar or starch – and making all sorts of renewable things, from fuels to commodity chemicals like plastics,” said Dean Toste, professor of chemistry and co-author of a report on the new development that will appear in the Nov. 8 issue of the journal Nature.
The work by Toste, coauthors Harvey Blanch and Douglas Clark, professors of chemical and biomolecular engineering, and their colleagues was supported by the Energy Biosciences Institute, a collaboration between UC Berkeley, Lawrence Berkeley National Laboratory and the University of Illinois at Urbana Champaign, and funded by the energy firm BP.
The linkage between Toste, whose EBI work is in the development of novel catalysts, and Clark and Blanch, who are working on cellulose hydrolysis and fermentation, was first suggested by BP chemical engineer Paul Willems, EBI associate director. The collaboration, Willems said, illustrates the potential value that can come from academic-industry partnerships like the EBI.
The late Weizmann’s process employs the bacterium Clostridium acetobutylicum to ferment sugars into acetone, butanol and ethanol. Blanch and Clark developed a way of extracting the acetone and butanol from the fermentation mixture while leaving most of the ethanol behind, while Toste developed a catalyst that converted this ideally-proportioned brew into a mix of long-chain hydrocarbons that resembles the combination of hydrocarbons in diesel fuel.
Tests showed that it burned about as well as normal petroleum-based diesel fuel.
“It looks very compatible with diesel, and can be blended like diesel to suit summer or winter driving conditions in different states,” said Blanch.
The process is versatile enough to use a broad range of renewable starting materials, from corn sugar (glucose) and cane sugar (sucrose) to starch, and would work with non-food feedstocks such as grass, trees or field waste in cellulosic processes.
“You can tune the size of your hydrocarbons based on the reaction conditions to produce the lighter hydrocarbons typical of gasoline, or the longer-chain hydrocarbons in diesel, or the branched chain hydrocarbons in jet fuel,” Toste said.
World War I process
The fermentation process, dubbed ABE for the three chemicals produced, was discovered by Weizmann around the start of World War I in 1914, and allowed Britain to produce acetone, which was needed to manufacture cordite, used at that time as a military propellant to replace gunpowder. The increased availability and decreased cost of petroleum soon made the process economically uncompetitive, though it was used again as a starting material for synthetic rubber during World War II. The last U.S. factory using the process to produce acetone and butanol closed in 1965.
Nevertheless, Blanch said, the process by which the Clostridium bacteria convert sugar or starch to these three chemicals is very efficient. This led him and his laboratory to investigate ways of separating the fermentation products that would use less energy than the common method of distillation.
The clear liquid at the top of the vial is glyceryl tributyrate, which extracts the acetone and butanol from the fermentation chamber. This allows chemists to more easily separate the chemicals from the yellow fermenting brew and protects the bacteria, which are killed by high concentrations of the chemicals.
They discovered that several organic solvents, in particular glyceryl tributyrate (tributyrin), could extract the acetone and butanol from the fermentation broth while not extracting much ethanol. Tributyrin is not toxic to the bacterium and, like oil and water, doesn’t mix with the broth.
Brought together by the EBI, Blanch and Clark found that Toste had discovered a catalytic process that preferred exactly that proportion of acetone, butanol and ethanol to produce a range of hydrocarbons, primarily ketones, which burn similarly to the alkanes found in diesel.
“The extractive fermentation process uses less than 10 percent of the energy of a conventional distillation to get the butanol and acetone out – that is the big energy savings,” said Blanch. “And the products go straight into the chemistry in the right ratios, it turns out.”
The current catalytic process uses palladium and potassium phosphate, but further research is turning up other catalysts that are as effective, but cheaper and longer-lasting, Toste said. The catalysts work by binding ethanol and butanol and converting them to aldehydes, which react with acetone to add more carbon atoms, producing longer hydrocarbons.
“To make this work, we had to have the biochemical engineers working hand in hand with the chemists, which means that to develop the process, we had learn each other’s language,” Clark said. “You don’t find that in very many places.”
Clark noted that diesel produced via this process could initially supply niche markets, such as the military, but that renewable fuel standards in states such as California will eventually make biologically produced diesel financially viable, especially for trucks, trains and other vehicles that need more power than battery alternatives can provide.
“Diesel could put Clostridium back in business, helping us to reduce global warming,” Clark said. “That is one of the main drivers behind this research.”
Coauthors of the study include former post-doctoral fellow Pazhamalai Anbarasan, graduate student Zachary C. Baer, postdocs Sanil Sreekumar and Elad Gross and BP chemist Joseph B. Binder.
RELATED INFORMATION
http://newscenter.lbl.gov/news-releases/2012/11/08/more-bang-for-the-biofuel-buck/
More Bang for the Biofuel Buck
Berkeley Lab Researchers Combine Old Fermentation Process For Making Explosives with New Chemical Catalysis to Boost Biofuel Production
November 08, 2012
(510) 486-5375 lcyarris@lbl.gov
6
News Release
The fermentation process used in World War I to make cordite for bullets and artillery shells might find new use today in the production of advanced biofuels.
Using the bacterium Clostridium acetobutylicum, the Berkeley Lab researchers fermented the sugars found in biomass into the solvent acetone and the alcohols butanol and ethanol, collectively known as “ABE” products. They then catalyzed these low carbon number products with the transition metal palladium into higher-molecular-mass hydrocarbons that are possible precursors to the three major transportation fuel molecules. The specific type of fuel molecule produced – whether a precursor to gasoline, diesel or jet – was determined by the amount of time the ABE products resided with the palladium catalyst.
“By catalytically upgrading ABE fermentation products we’re able to exploit highly efficient metabolic pathways and achieve near theoretical yields of transportation fuel precursors,” says Dean Toste, a chemist who holds joint appointments with Berkeley Lab and the University of California (UC) Berkeley. “With our technique, we can obtain about a gallon of fuel from 16 pounds of the sugars that can be derived from lignocellulosic biomass.”
From left, Harvey Blanch, Dean Toste and Douglas Clark led a research team that integrated biological fermentation with chemical catalysis to upgrade simple carbon chains into potential fuel molecules. (Photo by Roy Kaltschmidt)
Clostridium acetobutylicum is also known as the Weizmann organism after Chaim Weizmann, the chemist who first used the bacterium to ferment ABE products from starch. The bacterium rose to prominence during World War I when it was used by the British to ferment acetone for the production of cordite. C. acetobutylicum and the ABE fermentation process continued to be widely used until the 1950s when they were replaced by cheaper petrochemical-based processes.
With rising concerns about the release of excess carbon into the atmosphere as the result of burning fossil fuels, there is a renewed scientific effort to develop advanced biofuels for transportation energy. Synthesized from the sugars in the lignocellulosic biomass of grasses and other non-food plants, and produced in a sustainable manner, advanced biofuels could be carbon-neutral, meaning their use would not add excess carbon to the atmosphere. In addition, they would be renewable and non-polluting and represent a huge potential source of domestic jobs and revenue. Furthermore, unlike ethanol made from corn starch or sugarcane, advanced biofuels, if they could be successfully developed and produced cost-effectively, could be dropped into today’s vehicles with presumably with no impact on performance, and used in today’s infrastructures with no modifications required.
“In some ways, this work is a step back in time in which a very old fermentation process is being used with some new engineering and chemistry,” says co-author Blanch, one of the nation’s deans of biofuels research who also holds joint appointments with Berkeley Lab and UC Berkeley. “While there has been some progress in engineering microbes to produce advanced biofuels, the quantities produced thus far – technically, the solution’s titer – tend to be very limited. A hybrid method, combining microbial production with chemical catalysis, might provide a pathway to more efficient production of these advanced biofuels.”
Clostridium acetobutylicum can ferment the sugars found in biomass into the solvent acetone and the alcohols butanol and ethanol, collectively known as “ABE” products. Palladium can then catalyze these simple carbons into precursors for gasoline, diesel and jet fuel.
C. acetobutylicum ferments the sugars in lignocellulosic biomass into a product that is three parts acetone, six parts n-butanol, and one part ethanol, similar to how yeast ferments the sugars in grapes and hops into wine and beer. From a transportation energy perspective, the two-carbon chains of ethanol, three-carbon chains of acetone and four-carbon chains of butanol are mainly useful as additives to gasoline. However, the production of acetone in combination with the alcohols makes it possible to build longer hydrocarbons chains of gasoline, diesel and jet fuel.
“The key to our technology is the ability of C. acetobutylicum to produce acetone,” Toste says. “Acetone harbors a nucleophilic alpha-carbon, which is amenable to the formation of carbon bonds with the alcohols produced in ABE fermentation.”
To catalyze the build-up of these shorter carbon chains into longer fuel chains – a process called “alkylation” – Toste and his co-authors tested a number of transition metal catalysts, the workhorses of modern industry that are used to initiate virtually every industrial manufacturing process involving chemistry. The best performer they tested was palladium.
“In the first reactor, we remove the low-boiling ABE products from the fermentation broth using a high-boiling extractant, such as glyceryl tributyrate,” Toste says. “This removes toxic products from the organism, allowing for higher yields of ABE and a clean stream of product for chemical catalysis, which takes place in a second reactor. While palladium on carbon was the best catalyst in these tests, we have already identified other transition metal catalysts that could be even better.”
Toste believes that the integrative biological/chemical approach he and his colleague are reporting should be relatively simple to scale-up and implement on a commercial scale.
“The ABE fermentation process was established and scaled nearly a century ago,” he notes, “and while the chemistry portion is less proven on scale, it relies on heterogeneous catalysis, a mainstay of industrial chemistry today.”
Toste believes the combination of biological fermentation and chemical catalysis has important potential applications beyond the conversion of lignocellulosic biomass into transportation fuels and could become a powerful new technology-enabling tool.
“Many technologies today rely on either fermentation or chemical catalysis,” he says. “The idea of building integrated fermentation processes involving networks of catalysts is an exciting prospect.”
Adds co-author Blanch, “Integrating chemistry and fermentation is a useful way to capitalize on the best of both worlds. The chemistry described in our Nature paper is exciting because new carbon-carbon bonds are being formed between molecules and oxygen is being rejected without the need of hydrogenation. This results in very high yields.”
This research was funded by the Energy Biosciences Institute.
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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.Additional Information
For more about the research of Dean Toste go here
For more about the research of Harvey Blanch go here
For more about the Energy Biosciences Institute go here
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