While ethanol is typically produced from the starch contained in grains such as corn and grain sorghum, it can also be produced from cellulose. Cellulose is the main component of plant cell walls and is the most common organic compound on earth. It is more difficult to break down cellulose to convert it into usable sugars for ethanol production. Yet, making ethanol from cellulose dramatically expands the types and amount of available material for ethanol production. This includes many materials now regarded as wastes requiring disposal, as well as corn stalks, rice straw and wood chips or "energy crops" of fast-growing trees and grasses.
Producing ethanol from cellulose promises to greatly increase the volume of fuel ethanol that can be produced in the U.S. and abroad. A recent report found the land resources in the U.S. are capable of producing a sustainable supply of 1.3 billion tons per year of biomass, and that 1 billion tons of biomass would be sufficient to displace 30 percent or more of the country's present petroleum consumption.
Importantly, it offers tremendous opportunities for new jobs and economic growth outside the traditional "grain belt," with production across the country from locally available resources. Cellulose ethanol production will also provide additional greenhouse gas emissions reductions.
Building upon the strong foundation grain-based ethanol technology has provided, the ethanol industry is rapidly developing and expanding the number of feedstocks available for ethanol production. Iogen Corporation in Ottawa, Canada produces just over a million gallons annually of cellulose ethanol from wheat, oat and barley straw in their demonstration facility. In late 2007, Range Fuels broke ground on a 20 million gallon per year facility that will process ethanol from wood and wood waste in Georgia. Several existing ethanol plants in the U.S. are engaged in research and demonstration projects with the U.S. Department of Energy utilizing the existing fiber in their facility that typically goes into the livestock feed coproduct. Enzyme companies including Genencor International and Novozymes are working on research projects with the Department to significantly reduce enzyme cost and increase enzyme life and durability.
With continued advancements in pretreatment technology, fermentation, and collection and storage logistics, the commercial production of cellulose ethanol becomes more economically feasible.
Click here to learn more about the production of ethanol.
One way to produce cellulosic ethanol is through enzymatic conversion (pictured below). Other methods may include acid hydrolysis, gasification, or other technologis.
The Energy Independence and Security Act of 2007 (H.R. 6), signed into law in December 2007, contains a number of incentives designed to spur cellulosic ethanol production.
- Establishes definitions for the renewable fuels program, including advanced biofuels and cellulosic biofuels. Advanced biofuels is renewable fuel other than ethanol derived from corn starch that is derived from renewable biomass, and achieves a 50% greenhouse gas (GHG) emissions reduction requirement.
- The definition – and the schedule -- of advanced biofuels include two subcategories: cellulose and biomass-based diesel. Cellulosic biofuels is renewable fuel derived from any cellulose, hemicellulose, or lignin that is derived from renewable biomass, and achieves a 60% GHG emission reduction requirement. (Cellulosic biofuels that do not meet the 60% threshold, but do meet the 50% threshold, may qualify as an advanced biofuel.)
- Authorizes $500 million annually for FY08-FY15 for the production of advanced biofuels that have at least an 80% reduction in lifecycle GHG emissions relative to current fuels.
- Authorizes $25 million annually for FY08-FY10 for R&D and commercial application of biofuels production in states with low rates of ethanol and cellulosic ethanol production.
Click HERE for a more detailed summary of the celllose provisions in H.R. 6.
The concept of a biorefinery is modeled after petrochemical refineries, with production of multiple products at a single facility. Existing biorefineries include wet-mill corn processing and pulp and paper mills. As with petrochemical refineries, the vision is that the biorefinery would integrate several conversion processes to produce both transportation fuel (ethanol and biodiesel) and high-value chemicals or products, including ones that would otherwise be made from petroleum. Industrial biorefineries have been identified as the most promising route to the creation of a new domestic biobased industry.
