New Technology Could Lead to More Energy-Efficient
By Marcia Wood
June 26, 2007
Ethanol to fuel cars, trucks and
other vehicles might tomorrow take less energy to produce, thanks to a device
invented by Agricultural Research Service (ARS) scientists in California.
D. Offeman and
H. Robertson at the ARS
Regional Research Center in Albany, Calif., think it may be possible to cut
energy costs by using a series of specially designed permeable plastic sheets,
or membranes, to produce ethanol from fermented broths of corn, or straw and
other kinds of biomass feedstocks.
Bioethanol is taken out of an incoming
fermentation broth using this spiral-wound liquid membrane module. The broth
flows across the surface of specially designed permeable plastic membranes that
are wrapped around the module's perforated collection tube. Ethanol in the
broth is separated by the membranes, using a vacuum, then sent to other
equipment to be condensed into liquid. The leftover broth could be processed
into byproducts. Illustration courtesy
D. Offeman and
H. Robertson, USDA-ARS.
The technology will help to address the serious concern regarding the energy
efficiency of bioethanol production, according to
L. Fireovid, ARS national program leader for process engineering and
chemistry, Beltsville, Md.
The researchers' invention, called a spiral-wound liquid membrane module,
could potentially replace the widely used process of distilling ethanol from
fermentation broths. The module offers ethanol producers the important
advantage of combining two separation processes, extraction and membrane
permeation, in one piece of equipment.
With further research and development, the module would require less energy
than distillation. Today, energy costs are ethanol producers' second largest
expense; feedstocks are first.
In brief, the fermentation brothtypically containing about five to 12
percent ethanolwould travel through a sandwich-like configuration of
membranes and mesh sheets, called spacers, that keep the membranes separate
from each other. One membrane has a solvent in its pores that extracts the
ethanol from the broth. A second membrane, with the help of a vacuum, pulls the
ethanol out of the solvent. The ethanol-and-water vapor that results is then,
in other equipment, condensed into an ethanol-rich liquid.
The scientists have applied for a patent. They now plan to build and
fine-tune a prototype, then turn it over to a membrane manufacturer for further
development before commercialization.
Already, some ethanol producers have expressed interest in the invention.
The device has other potential uses, such as cleaning up wastewater or
treating natural gas for home use.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.