Scientists develop microbial fuel cell that converts cellulose into electricity by pairing bacteria

Scientists from the Penn State University have found a way to develop a microbial fuel cell (MFC) that produces electricity from cellulose. No currently known bacteria that allow termites and cows to digest cellulose can power a microbial fuel cell, and those bacteria that can produce electrical current cannot eat cellulose. But by carefully pairing two different bacteria the researchers succeeded in creating a fuel cell that consumes cellulose - the biosphere's most abundant organic compound - and converts it into renewable electricity.

They report the results of their study in a open access article in a recent issue of the journal Environmental Science and Technology.

John M. Regan, assistant professor of environmental engineering, said they had got microbial fuel cells to work with all kinds of biodegradable substances including glucose, wastewater and other organic wastes. But converting cellulose is trickier. There is no known microbe that can degrade cellulose and reduce the anode.

The researchers overcame this by putting together a microbe that can degrade and ferment cellulose and an anode-reducing bacterium that can live off the fermentation products.

Microbial fuel cells work through the action of bacteria that can pass electrons to an anode. The electrons flow from the anode through a wire to the cathode, producing an electric current. In the process, the bacteria consume organic matter in the water or sediment. More technically, the Penn State team describes MFCs as follows:

Using electrochemically active microorganisms as biocatalysts, microbial fuel cells are bioelectrochemical reactors that convert organic material directly into electricity. Unlike chemical or enzyme-based fuel cells, which are tailored to oxidize specific electron donors, MFCs have tremendous electron donor versatility. This includes simple substrates such as glucose, acetate, and lactate; complex substrates such as municipal and industrial wastewaters ; and even steam-exploded corn stover hydrolysate. MFCs can also be configured to produce hydrogen instead of electricity using an anaerobic cathode and a small applied voltage to reduce protons in the cathode chamber.

The interesting aspect of the new research is that the MFC works on cellulose, the material that holds so much potential for the production of renewable energy, but that is difficult to work with. Plants produce cellulose to use as their cell walls and to provide rigidity to their structure. Along with lignin and hemicellulose, they make up huge amounts of the biomass produced by plants. Some animals, ruminants and termites for example, can break down cellulose with the aid of bacteria that live in their digestive tract. Humans and most vertebrates derive little nutrition from cellulose.

The researchers, who include Regan, Thomas E. Ward, research associate and Zhiyong Ren, graduate student, looked at Clostridium cellulolyticum, a bacterium that ferments cellulose via its cellulase enzymes, andGeobacter sulfurreducens, an electroactive bacterium:
energy :: sustainability :: biomass :: cellulose :: cellulase :: bacteria :: microbial fuel cell :: anaerobic fermentation :: bioenergy ::

Both are anaerobic, living in places where no free oxygen exists. This fermenter produces acetate, ethanol and hydrogen. The electroactive bacteria consumed some of the acetate and ethanol.

"We thought that maybe we did not need a binary setup, maybe uncharacterized bacterial consortia would work" says Regan. "It worked, but not as well as the two specifically paired bacteria."

One problem with anaerobic bacteria - and the reason the researchers looked into an uncharacterized mixture of bacteria - is that currently the most efficient microbial fuel cells use an air cathode. Unfortunately, it is impossible to have an air cathode without some oxygen leaking into the reaction chamber, killing strictly anaerobic bacteria and reducing output. "We tried an aerobic cathode with the binary culture and it will not work," says Regan.

The researchers then settled on a two-chamber fuel cell that produced a maximum of 150 milliwatts per square meter. "We achieved a low power density because of the two chamber system," says Regan. "Current fuel cell designs produce about ten times that."

Currently the researchers are using pure, processed cellulose without any hemicellulose or lignin. They are just beginning to look at other cellulose products so the fuel cells can operate on less manufactured feedstock.

As a proof of concept, the researchers are happy with their results, but they would like to see the power density increase. One approach would be to find a community of bacteria that could tolerate small amounts of oxygen because some of the bacteria use up the oxygen before it reached the anaerobic bacteria. Another approach would be to improve the design of the oxygenless fuel cell.

Image: Structure of the cellulase enzyme Cel9G with which the bacterium Clostridium cellulolyticum breaks down cellulose. Credit: Institut de Biologie et de Chimie des Protéines.

References
Zhiyong Ren, Thomas E. Ward, and John M. Regan, "Electricity Production from Cellulose in a Microbial Fuel Cell Using a Defined Binary Culture", Environ. Sci. Technol., 41 (13), 4781 -4786, 2007. DOI: 10.1021/es070577h S0013-936X(07)00577-9, Web Release Date: June 6, 2007.

Eurekalert: Two bacteria better than one in cellulose-fed fuel cell - July 27, 2007.

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New center wins £1.1 million in funding for CCS research - towards carbon negative energy

Imagine you could develop an energy system that delivers electricity while at the same time taking historic carbon dioxide - the main culprit of climate change - out of the atmosphere. With such a carbon-negative energy system, you would effectively be 'cleaning up the past', not only the future. The electricity generated from such a concept could be used to power electric vehicles, homes and industry.

Such so-called 'Bioenergy with Carbon Storage' (BECS) systems become possible when biomass fuels (solid, gaseous or liquid) are burned in power plants that are integrated with a carbon capture and storage (CCS) system. The primary energy source is carbon-neutral because it consists of plants that take CO2 out of the atmosphere as they grow. When before, during or after the combustion of the biomass, its carbon dioxide is captured and then stored in suitable sites, the electricity generated becomes carbon-negative.

Scientists have looked at this BECS concept as one of the few feasible geo-engineering options to mitigate dangerous climate change on a large scale and in a safe manner that allows societies to use energy while taking historic CO2 emissions out of the atmosphere. The system is seen as a 'geo-engineering' technique because it involves the establishment large plantations of carbon capturing energy crops at strategic sites (earlier post).

Crucial to make the BECS concept work is the carbon capture and storage phase. Both steps are currently being tested and research has been speeding up with the idea to apply CCS to power plants that burn fossil fuels (in which case the system would still be slightly carbon-positive). One of the key risks associated with CSS is the potential for leakage: the carbon dioxide that will be stored in sites such as saline aquifers or deep coal seams could escape. Now if this were to happen in a CCS system that relies on fossil fuels, the entire concept would become unviable because the leaking CO2 gas would contribute to climate change. But if biofuels were to be used, leakage would be no problem, since there would be no net contribution. In short, as Biopact's Laurens Rademakers found, the use of biomass in CCS systems could be the safest way forward for the technology.

Other carbon storage techniques resulting in carbon-negative bioenergy are based on the sequestration of biochar in agricultural soils, or on processes that lock carbon dioxide up in useful products.

It is within this context that Biopact tracks the latest developments in CCS-research. Good news comes from the University of Nottingham, where Dr Mercedes Maroto-Valer, Associate Professor and Reader in Energy Technology, has won £1.1 million (€1.6/US$2.2 million) for a new centre that is set to play a crucial role in the development of CCS technologies.

The way we will approach this problem is unique. The CICCS will bring together engineers, mathematicians, bioscientists, geographers, geologists and end-users in a 'hot-house' environment that encourages creative problem-solving. - Dr Maroto-Valer, University of Nottingham, School of Chemical and Environmental Engineering

The Centre for Innovation in Carbon Capture and Storage (CICCS) — due to open in October 2007 — will develop novel technologies to trap and store greenhouse gases permanently and safely, so they are not released into the atmosphere.

One of the technologies that the Centre will work on uses a natural process in conjunction with silicate-based rocks such as serpentine. When put in a reactor and under a chemical reaction, CO2 gets locked in by the rocks permanently. The end-product is a mineral such as magnesite, which can be used as aggregates for road-building or shaped into bricks for construction. If applied to a CO2 stream from biomass, we could be building houses that store CO2 emissions from the past:
energy :: sustainability :: climate change :: fossil fuels :: carbon balance :: carbon capture and storage :: carbon sequestration :: BECS :: biofuels :: biomass :: bioenergy ::

The Engineering and Physical Sciences Research Council (EPSRC), through the Challenging Engineering initiative, has just announced the five-year funding package for CICCS, with a view to it becoming a world leader in the development of novel processes for carbon capture and storage and establishing partnerships with major international industries and research centres:

Dr Maroto-Valer who will be the director of the new center said: “The novel technologies developed at the Centre will enable the UK to meet its targets for the reduction of carbon dioxide (CO2) emissions, and thus help the UK to play its part in global efforts to tackle climate change.”

CO2 is the main culprit in global warming — and in the UK almost a third of these emissions come from power stations. The storage method to be developed at CICCS could cut such CO2 releases to almost zero in a safe and reliable manner.

The Centre will work on research at the interface of science and engineering, industry and international cooperation in order to accelerate technological innovation in the field and lead to a wider deployment of carbon capture and storage. The Centre will also have a strong programme of knowledge transfer and training with a range of opportunities for industrial engagement.

The Centre will promote interdisciplinary activity to bring groundbreaking ideas from basic science and develop them into new products, processes and services, as well as consider public acceptability issues.

Within the Centre a new generation of potential academic, industrial and government leaders in carbon capture and storage will be trained with a broad and interdisciplinary set of skills suitable for their future careers in industry, research or government.

Locking carbon dioxide into a useful product
One of the technologies that the Centre will work on uses a natural process in conjunction with silicate-based rocks such as serpentine, which is found in large enough quantities, and in the right places, to store all the CO2 produced by the combustion of the entire world's known fossil fuel reserves.

The CO2 extracted from burning coal is put into a reactor with the rocks and through a chemical reaction. The serpentine binds the carbon dioxide to itself, 'locking it in' permanently. This reaction does occur in nature — only far more slowly, taking place over eons of time.

Once the process is fully developed, it is estimated that the locking of CO2 will take place within minutes.

The end product is a mineral such as magnesite, which can be used as aggregates for road-building or shaped into bricks for construction. Carbon dioxide makes up 40 per cent of its weight and it would take 1,500 times more space to store the same amount in gas form.

Compared to other proposed processes for carbon storage, such as burying carbon under the sea, once the CO2 is locked inside the rock by the CICCS process, it is contained for good and cannot go back to its previous state. This is of paramount importance as ensuring the permanent storage of the CO2 has been the most controversial issue in carbon storage.

Moreover, the end result is a commercial product. Fossil fuel power plants could utilise the new process by adding a reactor to their emissions treatment system, allowing CO2 to be turned into a useful building material. The Centre's ultimate goal will be to sign collaborative agreements with power and construction companies to move forward with commercialisation of the technology.


A spokesperson for the EPSRC said: “Established in response to recommendations in the 2004 international review of engineering research in the UK, Challenging Engineering aims to encourage young researchers to develop and lead adventurous projects.

“It seeks to identify and support outstanding researchers at an early stage of their career, to achieve their potential faster through training in creativity and leadership, linking with industry, developing collaborative networks and routes to better exploitation.

“The competition required candidates to present their project proposals creatively and offered the opportunity to demonstrate their ability not only to lead far-reaching research, but also to communicate its importance to the wider world. The EPSRC makes around seven Challenging Engineering awards annually, with a total commitment of £16.3M to date.”


The processes developed by the Centre will also be attractive to oil producers, chemical manufacturers and other energy-intensive industries that have a role to play in helping the UK to meet its 2050 target of 60% reduction below 1990 levels.


The new Centre will without a doubt develop innovative ways to capture and store carbon dioxide. The first example - binding CO2 to rocks to yield a useful product - could be applied to any CO2 stream, including those coming from the combustion of solid, gaseous or liquid biofuels. This means we could soon be building our houses with bricks that contain CO2 from the past...


References:
The University of Nottingham: Nottingham centre to help UK to meet its carbon targets - July 27, 2007.

Biopact: Abrupt Climate Change and geo-engineering the planet with carbon-negative bioenergy - December 21, 2006

Biopact: Pre-combustion CO2 capture from biogas - the way forward? - March 31, 2007

Biopact: Carbon sequestration in deep coal seams feasible, but with risks - June 28, 2007

Biopact: Research warns 'dangerous climate change' may be imminent - carbon negative bioenergy now - May 31, 2007

Biopact: Report: clean coal and CCS 'feasible' in the UK - towards carbon negative energy? - May 15, 2007

EurActiv: 'Carbon-capture trials safest way forward' - Laurens Rademakers, Biopact - April 3, 2007.

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Progress Energy Florida to buy electricity from largest biomass gasification plant

As part of its ongoing growth in renewable energy and developing technologies, Progress Energy Florida (PEF) has signed a long-term contract to purchase electricity generated by what will be the largest waste-wood biomass plant in the U.S. In the past year, Progress Energy has signed contracts to add more than 200 megawatts of renewable energy to its system.

Biomass Gas & Electric (BG&E), based in Atlanta, Ga., plans to build a power plant in north Florida that will use waste wood products - such as yard trimmings, tree bark and wood knots from paper mills - to generate electricity. It will produce about 75 megawatts. The plant is expected to avoid the need to burn the equivalent of nearly 5 million tons of coal over the 20-year life of the contract, thus avoiding around 13.5 million tons of carbon dioxide emissions.

The southeast is the most biomass-rich area of the United States. Any comprehensive plan for energy production for the state of Florida should include renewable energy, and biomass must be an integral part of that plan. - Glenn Farris, president and CEO of Biomass Gas & Electric.

The green energy plant will use a gasification process to turn biomass into a gas that is directly substitutable for natural gas. To do so, it relies on the SilvaGas process developed by Future Energy Resources Corporation.

The process consists of the following steps (diagram, click to enlarge):

1. Wood chips or other biomass materials are loaded into the gasifier
2. In the gasifier the biomass is mixed with hot sand (1,800º F), turning it into product gas and residual char; a small amount of steam and the rapid release product gas provides the conveying force for the reaction
3. The residual char and cooled sand (1,500 º F) are separated from the product gas by a cyclone separator and discharged to the combustor
4. The sand is reheated in the combustor by adding air and burning the residual char; the reheated sand is removed from the combustion gas by a cyclone separator and returned to the gasifier
5. The product gas is cleaned in a scrubber and can be used for a variety of applications such as direct use in gas turbines, boilers, fuel cells or the production of chemicals
6. The flue gas is a valuable source of heat that can be recovered for uses such as biomass drying, steam production or direct heating

Projected commercial operation for the plant is expected to begin in 2011. It would be BG&E's third biomass power plant. The contract will be filed for consideration with the Florida Public Service Commission (PSC). The company seeks PSC approval of the contract and certification of the proposed plant as a qualifying facility under Florida laws and regulations that encourage renewable energy:
energy :: sustainability :: climate change :: greenhouse gas emissions :: coal :: biomass :: bioenergy :: gasification :: Florida ::

PEF purchases more than 800 megawatts from a number of qualifying facilities. They use various fuel sources, including biomass, waste heat from agricultural processes and municipal solid waste.

Last year, Progress Energy signed a contract with the Biomass Investment Group, to purchase the energy output (130 MW) from the nation's largest biomass plant to be built in Central Florida. The project, which will utilize environmentally friendly E-grass (earlier post) as its fuel source, will reduce carbon emissions by more than 20 million tons over the 25-year life of the contract when compared to coal.

Progress Energy Florida is a subsidiary of Progress Energy, and provides electricity and related services to nearly 1.7 million customers in Florida.

References:
Progress Energy Florida: Progress Energy Florida signs contract for renewable energy from biomass plant - July 26, 2007.

The SilvaGas process, overview.

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Researchers and producers optimistic about sweet sorghum as biofuel feedstock

In the U.S. corn is by far the largest carbohydrate source used to produce ethanol. But for a wide range of reasons, scientists are looking at alternative feedstocks. Sorghum has been identified as a promising candidate both in the U.S. (earlier post) and in the developing world (more here).

Dr. Bob Avant, program manager for the Texas Agricultural Experiment Station's bioenergy initiative, stands in front of tall sorghum being bred for biofuel production in College Station. Pictured front are hybrid sorghum varieties used in conventional cross-pollination with tall sorghum. The research effort is led by Dr. Bill Rooney, Experiment Station plant scientist. Credit: Texas Agricultural Experiment Station, photo by Jerrold Summerlin.

The tropical grass species narrowly related to sugar cane is robust, needs relatively small amounts of water and is being bred to become drought-tolerant and more sugar-rich. It can be grown and processed following a model that resembles the highly successful sugarcane ethanol industry in Brazil.

Dr. Bill Rooney, a Texas Agricultural Experiment Station researcher, is one of the scientists who hopes to contribute to this new vision by producing a high-tonnage and sugar-rich variety that could soon be used for bioenergy. His test field at the College Station shows a sorghum crop towering 12-feet high.

Sorghum as a source of biofuels had some of the U.S. top scientists at the recently held Great Plains Sorghum Conference enthusiastic about its future. The good thing is that the farmers who will have to grow the crop have joined the scientists in their optimism.

If modeled after the sugarcane industry, a tall sorghum variety producing 20-plus tons to the acre transported to a processing plant within a 40-mile radius would economically viable [50 tons per hectare and a radius of 65 km]. The sugarcane industry has been doing this for a long time. What we're not saying is switchgrass or corn isn't a viable crop, but if we can grow sorghum, it's worth giving a serious look. We believe this paradigm is happening and will happen. - Dr. Bill McCutchen, deputy associate director of the Experiment Station of Texas

Sorghum can play a pivotal role in the biofuel future because the crop needs far less water than corn while producing more biomass. But like corn, it can fit into first generation starch and sugar based conversions as well as in next-generation cellulosic ethanol pathways. And as in the Brazilian model, in a first instance, ethanol can be produced from the sugar of the crop, while its biomass residues (bagasse) could be used as a solid biomass feedstock for the production of green power at the conversion plant.

Sugar and water
Dr. Rooney's research has focused on improving sorghum as a bioenergy feedstock. The sorghum breeding program in College Station changed about four years ago, he told a group of researchers at the conference. On the side, they began working on bioenergy and sweet sorghums. It's meanwhile evolved into a project that has consumed a good portion of time.

Like sugarcane, sorghum can be converted into ethanol with relative ease. The tall sorghum trials in College Station boast superior genes from hybrid sorghums. Specifically, Rooney is evaluating the sorghum's sugar content. He wants to develop a high-sugar hybrid, but this means he needs have to have high levels of sugar on both sides of the parent.

Using cross-pollination of selected hybrid varieties, Rooney will soon establish a superior, high-yielding plant variety commercially viable for biofuel production. He's also attempting to include genetic traits that withstand periods of drought:
energy :: sustainability :: ethanol :: biomass :: bioenergy :: biofuels :: sweet sorghum :: sugarcane :: plant breeding :: genome ::

The tall sorghum trials are also being conducted in Weslaco and Lubbock. Another component of the research is harvesting. Rooney and other scientists are evaluating composition and yield both for animal feed and ethanol production, he said. One of the things they are looking at is to see how long can you leave the crop in the field.

Sugarcane model
The state of Texas is positioned to help meet the challenge of producing 1 billion tons of biomass needed to replace 30 percent of the America's petroleum, says Dr. Bill McCutchen, deputy associate director of the state's Experiment Station. Texas already is one of the largest biomass producers in the nation.

Using plant cellulose from Texas crops, such as sorghum, not only "has incredible potential, but also big potential for by-products", McCutchen told the conference.

According to McCutchen, sorghum produces more biomass than corn, using 33 percent less water. He thinks sorghum may have been overlooked as a potential biomass product.

If modeled after the sugarcane industry, a tall sorghum variety producing 20-plus tons to the acre transported to a processing plant within a 40-mile radius would economically viable [50 tons per hectare and a radius of 65 km].

The sugarcane industry has been doing this for a long time, McCutchen says. "What we're not saying is switchgrass or corn isn't a viable crop, but if we can grow sorghum, it's worth giving a serious look. We believe this paradigm is happening and will happen."

But how to incorporate these crops into an existing portfolio of feedstock crops and other cash commodities in Texas is a challenge that lies ahead. "One of the things we envision is we want to be able to grow dedicated biomass crops for fuel within a diverse system," he added.

The design of sorghum is being aided by the U.S. Department of Energy’s sorghum genome sequencing project and technology platforms developed by funding from the National Science Foundation. Acquiring fundamental knowledge about optimal sorghum biomass and biofuels design will aid in developing related biofuels crops such as corn, sugarcane, and switchgrass.

References:
Texas A&M University System Agriculture Program: Sorghum Producers Optimistic About Biofuel Potential - July 26, 2007.

Texas Agricultural Experiment Station: Designing Sorghum for the U.S. Biofuels Industry [*.pdf].

Bioenergy and biofuels research at the Texas Agricultural Experiment Station.

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Green Energy Resources receives biomass export order on strong European currencies

The record strength of the euro and the pound has some interesting consequences for the steadily growing international trade in biomass. The high euro/pound means petroleum imports are comparatively less costly for Europeans than for the U.S., because oil is quoted in dollars. On the other hand, American exporters benefit from the weak dollar and can ship goods competitively across the pond.

These two basic dynamics combined with record oil prices result in European interest in importing raw biomass from America that can be used to replace oil and coal in power plants.

In this context, New York based Green Energy Resources announces it has received a new export order for delivery of woody biomass to Europe. The order, contracted in British pounds, is for 40,000 tons delivered or about $2.6 million dollars. The shipment is subject to ship scheduling and planned for later this year. The shipment will be the first biomass export to the UK from North America.

High oil prices make alternative energy production very cost effective to power producers. Oil is nearing $80 per barrel and US consumption in 2007 is exceeding that of 2006. The US dollar is currently about .45 cents to the British pound and about .62 cents on the Euro. Green Energy Resources has targeted a 20% market share of European biomass imports by 2011. The European biomass market should exceed $1 billion dollars by 2010 according to various European agencies

According to Green Energy Resources, biomass continues to be the workhorse of the renewable energy industry leading solar and wind energy production by more than double, according to the US Department of Energy 2006 statistics. A property that sets biomass and biofuels apart from other renewables is the fact that it can be physically traded, allowing producers and consumers to target markets in a dynamic way:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: wood :: exchange rate :: trade ::

According to EurObeserver's latest Solid Biomass Barometer, in 2005 primary solid biomass production for energy in the EU increased markedly with 3.1 million tonnes of oil equivalent (Mtoe) compared to 2004. The increase in the price of fossil fuels and the necessity for politicians to take environmentally sound decisions has had positive effects on the biomass sector in 2005. The biomass market in Europe is maturing, which means the gates are opening biomass trade.

Electricity production from solid biomass has increased markedly between 2004 and 2005 with a growth of 16.1%, according to the barometer mainly due to the establishment of biomass fired combined heat and power (CHP) plants in Germany and the Netherlands (earlier post).

References:
dBusinessNews: High Oil and Record Currency exchange rates are Great News for alternative energy exports for Green Energy Resources - July 27, 2007.

Biopact: Solid biomass production for energy in EU increases markedly - December 21, 2006

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