Biotechnology for biomass conversion

Introduction

Ethanol is the principal liquid fuel made from renewable resources. In Brazil, approximately 3.2 billion gallons of ethanol is made from sugarcane for automotive use every year. At present, the U.S. agricultural industry provides approximately 1.2 billion gallons of ethanol from corn and other agricultural crops to produce clean-burning high oxygenate fuel blends. Bioconversion of domestically produced, renewable biomass feedstocks into ethanol could provide 20% of the transportation fuels used in the United States. By the year 2010, renewable biofuels could be providing 14 billion gallons of ethanol a year -- approximately 10% of the total fuel used for automotive transportation. Other renewable fuels include biodiesel and hydrogen

Jobs and agricultural incomes: Renewable fuel production provides jobs in rural areas while reducing dependency on imported petroleum. Byproducts of ethanol fuel production from corn are high-nitrogen feeds, oils and fiber. Only a fraction of total corn production is used to make ethanol, and most of the animal feed value is recovered in the byproducts. Corn production from existing farmland could provide approximately 5 billion gallons of ethanol per year without disrupting food prices. Much more ethanol could be recovered by developing technology for the conversion of corn fiber, corn cobs, corn stalks, and other wood and other agricultural residues.

Ethanol from wood: The potential for ethanol production from wood and other lignocellosics is much greater than that from corn. Wood harvesting operations can produce large quantities of wood residues that can be used for ethanol production. Excess growth in unmanaged forests can produce large quantities of small diameter, low-grade wood. In many areas, excess dead, down and diseased timber accumulates to present a fire hazard. These materials could likewise be converted into ethanol and other fuels.

Waste streams: Many industrial and municipal waste streams can be converted into renewable fuels. Timber harvest residues, cellulosic fiber fines from paper mills, low-grade mixed waste papers all comprise useful feedstocks for ethanol production.

Energy crops: Using liquid fuels from renewable biomass can actually decrease the accumulation of greenhouse gases while providing clean, efficient energy for transportation. In the future woody and herbaceous bioenergy crops could provide clean-burning fuels for a renewable fuel economy. Examples of such crops include fast growing poplar, willow, and various perennial grasses. Entrepreneurs and investors with vision and the access to appropriate technologies can tap into these abundant renewable, environmental resources.

Environmental benefits: One of the principal benefits of ethanol from biomass fuels is that it provides a storable transportation fuel while reducing the effects of greenhouse warming. During growth, plants remove carbon dioxide from the air and convert it into starch, cellulose and hemicellulose. Fermentation converts these carbohydrates into ethanol which is in turn converted back into carbon dioxide when used for fuel. This closed cycle makes no net contribution to the accumulation of carbon dioxide in the atmosphere. Ethanol is also a clean-burning fuel, and by substitutiong ethanol for benzene and polycyclic aromatics in gasoline, fuel toxicity can be reduced.

There are many possible paths to successful bioconversion, and the exact combination employed will depend on the specific opportunity. The principal components include an abundant biomass feedstock, an appropriate pretreatment, saccharification, fermentation and recovery technology.