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Microbes hold the key to turning paper cellulose waste into fuel, Rehovot Scientist says
...Cellulose, the tough plant molecule found in paper and plant products such as lawn clippings, is one of the most abundant components in landfills.
About 35 percent of landfill waste is paper, making it the single-largest contributor to landfills, according to the U.S. Energy Information Administration. Add to that lawn and garden trimmings and vegetable leftovers, and that makes up most of the volume occupied by landfills. Collectively, these cellulose-containing materials are known as "biomass."
Scientists think they can unlock the power of cellulose and turn it into fuel. The secret to doing so, they say, lies in the few microbes that can digest cellulose, such as those living in the guts of termites. They contain special enzymes that, if assembled in the right way, hold great promise for breaking apart one of nature's most durable organic molecules. The challenge lies in taming these enzymes to human needs, and making them cheaply in sufficient quantities.
Cellulose is nothing more than a long chain of sugar molecules. Sugar contains energy. So if cellulose could be turned into sugar, it would become a vast new source of fuel. Sugar could fuel bacteria-powered cells or be fermented into ethanol. Such "cellulosic ethanol" would represent a new source of ethanol to replace gasoline. Cellulosic ethanol is now in experimental production.
Large-scale use of cellulose as an energy source has proven impractical until now. Traditional chemical methods break up cellulose by treating it with acids and high temperatures. That's proven too expensive to produce wholesale ethanol.
Cellulose is durable
The chemical bonds that hold cellulose together are very strong, making the molecule extremely stable, said Edward A. Bayer, a researcher at the Weizmann Institute of Science in Rehovot, Israel. Bayer gave a talk on strategies for using cellulose at last week's Genome, Medicine and the Environment conference in San Diego.
Cellulose can last for thousands of years. The oldest living things are bristlecone pines, most of which are made up of dead wood. The most ancient of these hardy survivors are nearly 4,800 years old.
Even in a landfill, cellulose retains its nearly impervious nature. In his talk, Bayer showed slides from excavations of a landfill at Tel Aviv. Its cellulose-containing products included a newspaper still legible after 50 years, corncobs and even a seven-year-old head of lettuce.
"Even organic material or food is relatively stable in a landfill," Bayer said. "What gets in there (stays) more or less forever."
That's the kind of durability mankind is up against in turning cellulose into a nonpolluting fuel, Bayer said.
"We have to kind of trick nature do to something it doesn't want to do for our purposes," Bayer said.
The hope of Bayer and other scientists in the field rests on genetically re-engineering naturally occurring enzymes that cut cellulose into smaller molecules that can be digested.
These enzymes come in two classes. One is the "cellusome," a ball of enzymes produced by certain anaerobic bacteria in very small quantities. These are very efficient in breaking down cellulose. Some fungi and aerobic bacteria produce a different class of cellulose-degrading enzymes in large quantities, but these enzymes are far less efficient.
Either class of enzymes would work, he said.
"The bottleneck is economical production of the enzymes," Bayer said. "However, if fuel prices continue to go up, we won't have to do much in the future."
Laboratory experiments with modified cellusomes in Bayer's team and among other scientists have increased these enzymes' efficiency, Bayer said. They've tested straw and switchgrass, a rising star among ethanol sources, among other materials.
Genes for making these cellusomes could be incorporated into bacteria or yeast that would ferment such materials. Another possibility is to genetically engineer plants such as switchgrass to make these cellulose-degrading enzymes...
Source: Bradley J. Fikes. Microbes hold the key to turning waste into fuel. NCTimes.com (14 October 2007) [FullText]
About 35 percent of landfill waste is paper, making it the single-largest contributor to landfills, according to the U.S. Energy Information Administration. Add to that lawn and garden trimmings and vegetable leftovers, and that makes up most of the volume occupied by landfills. Collectively, these cellulose-containing materials are known as "biomass."
Scientists think they can unlock the power of cellulose and turn it into fuel. The secret to doing so, they say, lies in the few microbes that can digest cellulose, such as those living in the guts of termites. They contain special enzymes that, if assembled in the right way, hold great promise for breaking apart one of nature's most durable organic molecules. The challenge lies in taming these enzymes to human needs, and making them cheaply in sufficient quantities.
Cellulose is nothing more than a long chain of sugar molecules. Sugar contains energy. So if cellulose could be turned into sugar, it would become a vast new source of fuel. Sugar could fuel bacteria-powered cells or be fermented into ethanol. Such "cellulosic ethanol" would represent a new source of ethanol to replace gasoline. Cellulosic ethanol is now in experimental production.
Large-scale use of cellulose as an energy source has proven impractical until now. Traditional chemical methods break up cellulose by treating it with acids and high temperatures. That's proven too expensive to produce wholesale ethanol.
Cellulose is durable
The chemical bonds that hold cellulose together are very strong, making the molecule extremely stable, said Edward A. Bayer, a researcher at the Weizmann Institute of Science in Rehovot, Israel. Bayer gave a talk on strategies for using cellulose at last week's Genome, Medicine and the Environment conference in San Diego.
Cellulose can last for thousands of years. The oldest living things are bristlecone pines, most of which are made up of dead wood. The most ancient of these hardy survivors are nearly 4,800 years old.
Even in a landfill, cellulose retains its nearly impervious nature. In his talk, Bayer showed slides from excavations of a landfill at Tel Aviv. Its cellulose-containing products included a newspaper still legible after 50 years, corncobs and even a seven-year-old head of lettuce.
"Even organic material or food is relatively stable in a landfill," Bayer said. "What gets in there (stays) more or less forever."
That's the kind of durability mankind is up against in turning cellulose into a nonpolluting fuel, Bayer said.
"We have to kind of trick nature do to something it doesn't want to do for our purposes," Bayer said.
The hope of Bayer and other scientists in the field rests on genetically re-engineering naturally occurring enzymes that cut cellulose into smaller molecules that can be digested.
These enzymes come in two classes. One is the "cellusome," a ball of enzymes produced by certain anaerobic bacteria in very small quantities. These are very efficient in breaking down cellulose. Some fungi and aerobic bacteria produce a different class of cellulose-degrading enzymes in large quantities, but these enzymes are far less efficient.
Either class of enzymes would work, he said.
"The bottleneck is economical production of the enzymes," Bayer said. "However, if fuel prices continue to go up, we won't have to do much in the future."
Laboratory experiments with modified cellusomes in Bayer's team and among other scientists have increased these enzymes' efficiency, Bayer said. They've tested straw and switchgrass, a rising star among ethanol sources, among other materials.
Genes for making these cellusomes could be incorporated into bacteria or yeast that would ferment such materials. Another possibility is to genetically engineer plants such as switchgrass to make these cellulose-degrading enzymes...
Source: Bradley J. Fikes. Microbes hold the key to turning waste into fuel. NCTimes.com (14 October 2007) [FullText]
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