University of Illinois crop sciences professor Stephen P. Long spoke this May at the Vatican on the use of biological wastes and non-food crops to produce biofuels. His talk was part of a week of study at the Pontifical Academy of Sciences in Vatican City on the use of genetically modified organisms (GMO) to address the needs of the poor. Professor Long spoke to News Bureau life sciences editor Diana Yates about how new technologies are advancing the development of second-generation biofuels.
When they hear the word "biofuels," most people think of corn ethanol. What other types of biofuels are being developed?
Production of ethanol made from sugar cane in southeast Brazil is likely to exceed that of corn ethanol soon. Like other countries that produce sugar, Brazil saw a large loss of market as global demand for sugar declined. With flex-fuel vehicles now the norm in Brazil, 40 percent of their transportation fuel is now from homegrown sugar cane ethanol. Combustion of cane residue also powers their ethanol factories and generates a significant part of the country's electricity. From a greenhouse gas and global climate change perspective, this is an excellent development. It is displacing fossil fuels and is largely being achieved by replanting abandoned sugarcane fields. Brazil is investing some $250 million (US dollars) to improve the economic and environmental sustainability of the process. It is our best example that biofuels are more than corn ethanol.
Increasing global demand for Midwest corn as an animal feed makes its use for ethanol less attractive and has raised the specter of competition between food and fuel. But there are ways of producing biofuels without competing with staple food and feed crops. All plant material - including wood, straw and grass - is made up largely of sugars. The structure of a plant comes from celluloses, which, like starches, are chains of sugars joined together. Celluloses are just more difficult to convert back to sugars than starch. Grazing animals and insects such as termites obtain their energy by breaking down celluloses to their component sugars. Simulating the same process in factories and then fermenting the sugars to ethanol, butanol or other fuels will allow us to produce so-called "cellulosic fuels" from any plant material.
How might new research change how we think about biofuels?
Cellulosic biofuels are not new. In the early 1900s cellulosic ethanol was made by digesting wood in acids and then fermenting the sugars released to ethanol, producing about 50 gallons of ethanol from a dry ton of wood or straw. New research has allowed us to double this yield without using acids and with much less water. Perennial plants can provide high yields of biomass, and require few or no chemical inputs such as nitrogen fertilizers. Perennials also prevent erosion, build soil carbon and remove the need for annual cultivation. Switchgrass, energy cane and poplars are often used. At Illinois we have researched Miscanthus, a perennial grass that produces record amounts of biomass with no added nutrients. In Illinois it grows well on marginal lands. Spartina, a similar grass, thrives on saline soils where no other crops can be grown. We are also looking at Agaves, the source of sisal and tequila, which yield less biomass than Miscanthus, but will grow on the degraded semi-arid soils of the southwest without irrigation. Together these new sustainable crops could provide enough biomass to replace much of our gasoline with cellulosic biofuels without impacting food production.
Researchers are also discovering naturally occurring enzymes for breaking down biomass, and the genes that encode them. For example, enzymes in the digestive systems of cows and termites are more effective than acids in releasing sugars from biomass. Several of these enzymes are now available commercially and are more environmentally benign. Except for a small amount of butanol, all biofuel today is ethanol. Unfortunately, ethanol mixes with water and is expensive to separate from water. Many biological organisms make oils and waxes that do not mix with water and are more similar to gasoline. The genes involved in making these oils are being engineered into bacteria and yeasts, so that instead of fermenting sugar to ethanol these organisms will ferment sugars to oils. This will greatly decrease the amount of energy and water needed to make the fuel.
Will these new approaches be useful to people in developing countries or only benefit wealthy nations?
The example of Brazil shows us that this can be beneficial to the economy of developing countries. Brazil is already providing assistance to less well-off nations with the potential to duplicate its success with sugar cane. It is also a leader in the development of cellulosic fuels. However, cellulosic fuels, particularly the promising fermentation to oils, require the development and use of genetically modified organisms (GMOs) and regulatory testing requirements developed in Europe and North America for GMOs have become the norm. Meeting these requirements can be a multi-million dollar expense. This is likely to limit these technologies to the multi-nationals with the deepest pockets.
How long will it take to develop affordable, carbon-neutral biofuels to replace gasoline and other petroleum fuels?
The first commercial cellulosic ethanol plants in the U.S. are now in construction, and we should see ethanol from these within a year or two. However, this is only a start, and more efficient systems will be needed. We know how to grow the new second-generation crops such as Miscanthus, poplars, and Spartinas. And we know how to break down their biomass into sugars and ferment the sugars to oils, so no major scientific breakthroughs are required. Rather we need to increase the economic and environmental efficiency of each step, primarily through biotechnological engineering. This approach has already been used in biomedicine; for example, cloning the genes for making insulin into bacteria. Now these technologies are being applied to biofuel production. The speed of such incremental technological improvement depends largely on the investment made. At present investment levels an affordable process should be in place within five to 10 years.