Cellulosic Ethanol

August 8, 2007

Cellulosic ethanol is very much in the news nowadays.

Cellulosic ethanol is ethanol made from plant biomass such as agricultural wastes and forest residues. Plant biomass is another term for the tissue of recently dead plants, or plants that grow and die annually. This is in contrast to plant matter that died eons ago and over time created our current supply of carbon fuels, namely coal and oil.

In February of this year, the US Department of Energy (DOE) selected six companies to construct demonstration "biorefineries" that will produce energy and fuels from biomass. The funding was set at US$ 385,000,000. A variety of biomass materials were addressed:

Abengoa Bioenergy is focusing on producing ethanol from corn stover. Corn stover, sometimes called forage or silage, is the cob, husk, stalk and stem of corn plants. Abengoa is likely to use a "steam explosion" process to pre-treat the stover prior to enzymatic hydrolysis. Sugars liberated in the process are fermented to produce ethanol.

Verenium is a company recently formed by the merger of Diversa and Celunol. Diversa is in the production of enzymes, while Celunol has their ethanol facility in Jennings, Louisiana. Verenium is focused on producing ethanol from sugar cane bagasse. Bagasse has the advantages of sugar content and a long growing season. Its agricultural base is especially strong in Brazil.

Metabolix is focused on genetically modified switch grass. Switch grass, also known as prairie grass, grows over much of the United States and northern Mexico. It has the advantages of growing with minimal cultivation, with multiple harvests per season.

Here in Florida, there is strong political support for producing cellulosic ethanol from citrus waste. Several projects have been announced. One disadvantage is the relatively short, 150 day, orange harvest season. More significantly, there are technical barriers to be overcome in processing the spent orange peel once it has been fermented to produce alcohol.

Currently Vincent presses are being used in five different, albeit minor, projects based on producing cellulosic ethanol from sweet sorghum. See a previous Pressing News, #181 Sweet Sorghum, for details.

Our presses suit several applications: extracting juice from biomass, dewatering between the stages of counter flow washing, and final pressing ahead of a dryer. Our expertise in the manufacture of vapor-tight screw presses is also important.

Vincent screw presses are in operation in a surprising number of cellulosic ethanol operations. All of these activities started with the renting small screw presses, for trials, testing, and pilot runs.

Issue 192