|
The vast bulk of plant material consists of cellulose, hemicellulose, and lignin (as opposed to starch and sugar that industry currently converts to ethanol and uses to make food and feed products). The U.S. Department of Energy's Biomass Program is at the forefront of a national effort to develop technology to break cellulose and hemicellulose down into their component sugars. Anticipated biorefineries will then be able to biologically process these sugars to fuel ethanol or other building block chemicals. Lignin can either be burned to provide process heat and electricity or can itself be converted to fuels and chemicals.
This lignocellulosic biomass technology will enable the development of biorefineries that produce an array of valuable chemicals and products together with bulk biofuels needed for the transportation sector to alleviate dependence on foreign oil, reduce net greenhouse gas emissions, and mitigate other environmental problems. There are a variety of technologies for hydrolyzing biomass — breaking it down into its component sugars. Although other hydrolysis technologies such as concentrated acid and dilute acid have long industrial histories, the Biomass Program focuses on enzymatic hydrolysis as the most promising for reducing the cost of producing fuel ethanol and enabling biorefinery development.
After mechanical milling, the Biomass Program process design for the sugar platform starts with dilute-acid thermochemical pretreatment. This hydrolyzes the hemicellulose, breaking it down into its component sugars (xylose and others). It also solubilizes some of the lignin. Because cellulose is naturally wrapped in a sheath of hemicellulose and lignin, both of these actions make the cellulose more accessible to further action. The cellulose is then enzymatically hydrolyzed to release its sugars (glucose). The biomass sugars so produced are then available for fermentation to fuel ethanol or to bio/catalytic processing to other products, and the residue lignin is available for catalytic conversion to other products, gasification, or combustion to provide heat and power for the plant's operation or export.
At the more basic research end of the spectrum, the Biomass Program also researches the scientific fundamentals underlying sugar platform technology, as well as new concepts that hold promise to greatly improve overall processing economics. At the applied end of the spectrum, the Program's sugar platform integration efforts seek to resolve practical challenges involved in industrial scale application of sugar platform technology. The program also works extensively to develop "bridges" between future biomass-to-ethanol technology and the current ethanol industry, to exploit the many opportunities that exist for adopting or advancing cellulosic ethanol production or other sugar platform technologies.
|
){kind=small}
