Finding a cheaper way to make ethanol from biological waste products is a top priority around the world. Researchers at dozens of companies addressing the problem say they may find the answer in tiny bioreactors that turn wood into sugar. These centimeter-long chemical factories aren’t the product of a government lab or an industry consortium but of millions of years
Right now, the primary feedstock for ethanol produced in the United States is corn. Last year, nearly 2 billion bushels, representing one-fifth of the U.S. corn harvest, were used to produce automotive fuel. The resulting 18 billion liters of ethanol were enough to meet roughly 4 percent of the country’s 1.45â''billion-liter-a-day fuel demand. The U.S. Department of Energy’s goal is to replace 30 percent of the gasoline with biofuels by 2030.
But as demand for ethanol increases and dozens of refining plants for the fuel come online, the competition between food and fuel is causing the price of corn to pop. This has consequences well beyond U.S. borders: 70 percent of the corn imported by other countries is grown in the United States.
The search is on for a way to end the food-vs.-fuel competition by converting woody plant matter to simple sugars that can be fermented into ethanol as readily as starch-laden ears of corn are today. Corn would remain food for humans and livestock, while cornstalks and other biomass, such as switchgrass and even the grass clippings from your lawn, would be turned into fuel.
But getting a cornstalk into your fuel tank is easier said than done. Nature has made most trees and plants resistant to being broken down. Scientists all over the world are exploring ways of converting woody mass to ethanol more efficiently--everything from devising chemicals to break down cellulose to genetically engineering plants that can be turned more readily into sugar. Getting at the termites’ secrets is just one approach, but it’s a promising one. Termites certainly have what it takes to overcome nature’s recalcitrance [see photo, "Creative Destruction"], but what exactly is it?
We know that hundreds of species of fungi and bacteria in the guts of termites work cooperatively, secreting enzymes that break down the hard, fibrous cellulose, lignin, and other materials that give plants and trees their rigid structures. As yet, however, scientists have been unable to reproduce individual species of micro-organisms in the lab because they still know very little about what each one eats and secretes in the microbial soup bowl that is the termite’s digestive tract. So researchers are employing a workaround that they hope will allow them to reliably tease out these organisms’ various demolition methods.
Dozens of companies around the world are applying the techniques that were used to sequence the human genome in an attempt to create designer versions of the enzyme cocktails secreted by these microbes. Instead of trying to grow the organisms, researchers are cloning the genes that code for the desired enzymes and splicing them into common bacteria that are good media for reproduction. Once the genes are reproduced by the bacteria, they can be stored and subsequently used in experiments aimed at figuring out which combinations of enzymes are most effective at breaking down particular types of biomass. The enzymes are also engineered so that less pretreatment of the feedstock is required during the processing phase.
That’s why termites have gained a measure of esteem. If they turn out to have the key to making ethanol production from biomass economically feasible, then what was once just waste will be a valuable commodity.
”Not long ago, rice producers were asking if we could make paper out of [the waste product] rice straw, because environmental abatement rules said they could no longer burn it and they didn’t know what to do with it,” says Arthur J. Ragauskas, a biochemistry professor at the Georgia Institute of Technology, in Atlanta. ”Now those unwanted leftovers are poised to become a basic resource for biofuel.”
Some companies are already making ethanol from woody material, but not on a commercial scale, says Kevin Gray, director of alternative fuels at Diversa Corp., in San Diego, one of the companies refining the enzymes found in termites’ innards. In April 2004, Iogen Corp., an Ottawa-based biotech firm, became the first business to sell cellulosic ethanol. It operates a facility that each day processes 30 metric tons of wheat, oat, and barley straw, using enzymes that, though not derived from termites, turn the chaff into sugar.
Iogen’s demonstration plant turns out 2.5 million liters of ethanol a year--a drop in the bucket considering that, on average, an equivalent amount of gasoline is consumed in the United States every 2.5 minutes. An Iogen spokesman noted that a commercial facility would, in the future, process upwards of 700 metric tons of feedstock per day, yielding approximately 75 million liters of ethanol per year.
But Gray explains that in order to reach commercial viability, enzymatic reactions and other steps in the biomass-to-ethanol process, including the chemical pretreatment of feedstock, have to be optimized. And, he says, the cost has to be reduced by about a factor of five.
Gray and other scientists are optimistic that as they learn more about life inside termites’ guts--and, too, as plants are genetically engineered to more readily turn to sugar--the production of cellulosic ethanol will ensure that corn remains on dinner plates instead of at fuel pumps. Asked when commercial production of ethanol from biomass would begin, Gray said it might be possible in as little as five years.