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INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE
Improving Biofuels Recovery Processes for Energy Efficiency and Sustainability
Introduction
Biofuels are made from living or
recently living organisms. For
example, ethanol can be made from
fermented plant materials.
Biofuels have a number of important
benefits when compared to fossil
fuels. Biofuels are produced from
renewable energy sources such as
agricultural resources. When used
in place of imported fossil fuels,
biofuels can help reduce U.S.
dependence on foreign oil. Biofuels
can also have fewer environmental
impacts than fossil fuels.
The 2007 Energy Independence and
Security Act (EISA) called for
increased biofuel production. The
EISA also set standards for
renewable fuels achieving 20, 50,
and 60% reductions in greenhouse
gas (GHG) emissions relative to
fossil fuels.
GHG emissions from renewable
fuels are primarily due to feedstock
production, conversion of feedstock
to fuel (upstream emissions), and
fuel use. For corn-based ethanol,
about 50% of the energy consumed
in the production facility is due to
the separation processes of
distillation and adsorption used to
recover and dry ethanol from
fermentation broths, leading to
significant upstream GHG
emissions.
Method
The US EPA has proposed that
pervaporation and vapor permeation,
two emerging membrane
technologies, can provide energy
savings and reduce product recovery
costs over traditional technologies,
especially for smaller systems.
Pervaporation involves the selective
permeation and evaporation of
compounds in a liquid feed into a
vapor phase. For example, an
alcohol-selective membrane yields
concentrated ethanol vapors from
dilute solutions. A water-selective
membrane yields water-enriched
vapors while dehydrating the feed
liquid. EPA researchers have also
used pervaporation in other
environmental applications (ex. the
separation of chlorinated solvents
and gasoline organic compounds
from the water and surfactant
solutions used in soil flushing).
Vapor permeation is identical to
pervaporation except all process
streams are vapors.
Goal
A goal of this research is to
demonstrate at the pilot-scale the
recovery of ethanol from the
fermentation of a waste biomass.
The research helps make the biofuel
system as environmentally neutral,
energy-efficient and sustainable as
possible.
Vapor Permeation Results
EPA researchers evaluated hybrid
systems which synergistically
combine vapor permeation
membrane systems with traditional
separations such as distillation.
Membrane Assisted Vapor Stripping
(MAVS), a hybrid system developed
at EPA (see picture and schematic),
was predicted to deliver fuel-grade
ethanol using 50% less energy than
current separation technologies. In
MAVS, the stripping column obtains
high alcohol recoveries and low
effluent concentrations. The vapor
compressor and membrane enable
the efficient recovery of latent and
sensible heat from both the retentate
and permeate vapor streams.
The EPA team evaluated the energy
savings of MAVS through chemical
process simulations and verified the
predictions with experiments on a
five weight percent ethanol aqueous
feed stream.
Membrane Assisted Vapor Stripping
unit at EPA 's Test & Evaluation
Facility.
Pervaporation Collaborations
and Results
Through a cooperative research and
development agreement, EPA and
Membrane Technology & Research,
Inc. (MTR) demonstrated a new
method for recovering and
concentrating ethanol and other
organic chemicals from water. The
U.S. Environmental Protection Agency
Office of Research and Development
EPA600/F-11/018
June 2011
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approach combines pervaporation
with a vapor condensation
technology called dephlegmation.
An MTR pervaporation pilot unit
was integrated with the EPA
dephlegmator at the EPA's Test &
Evaluation Facility in Cincinnati,
Ohio to evaluate the ethanol
recovery performance of the
combined technologies. Results
have been quite promising. The
combined technologies concentrated
a stream containing 1 to 5 weight
percent ethanol to over 90 weight
percent ethanol. This MTR/EPA
project was funded, in part, through
a Phase I Small Business Innovative
Research grant to MTR from the
National Science Foundation.
In collaboration with several
industrial and academic partners,
EPA's Pervaporation Team has
demonstrated a novel pervaporation-
based ethanol recovery technology
which enables the economical
production of ethanol from biomass
readily available throughout rural
areas. One project targeted whey, a
byproduct of cheese production. A
typical cheese facility generates
enough whey to produce around 1-2
million gallons of ethanol per year
(MGY). Though the capacity of one
whey-to-ethanol
facility is much smaller than the 50
MGY capacity of a typical corn-to-
ethanol facility, the ethanol
production from hundreds of cheese
facilities would be substantial.
Because of the high water content of
whey, it is uneconomical to transport
the material to a centralized ethanol
production facility. A solution to this
problem is an efficient, small-scale
ethanol production and recovery
system that enables the production
of ethanol from cheese whey and
other low-volume byproduct and
waste streams.
EPA collaborated with membrane
producer MTR, researchers from
Argonne National Laboratory, and
potential end-user Kraft Foods. The
recovery of ethanol from a simulated
whey process stream was
demonstrated at the EPA's Test &
Evaluation Facility.
Current Work
The MAYS technology is being
further developed through a
cooperative research and
development agreement with MTR.
The EPA and MTR are working
with several potential end-users to
adapt the technology to their biofuel
production processes.
References
L.M. Vane, F.R. Alvarez, Y. Huang and
R.W. Baker, Experimental validation of
hybrid distillation-vapor permeation
process for energy efficient ethanol-
water separation. J Chem Tech
Biotechnol 85:502-511 (2010).
L.M. Vane and F.R. Alvarez, Liquid
separation by membrane assisted vapor
stripping process. US Patent Application
20090057128 (2009).
L.M. Vane, "Separation technologies for
the recovery and dehydration of alcohols
from fermentation broths," Biofuels,
Bioproducts and Biorefining, 2, 553-588
(2008).
Contacts
Leland M. Vane, Ph.D., Office of
Research & Development, 513-569-
7799, vane.leland@epa.gov
Franklin Alvarez, Office of Research &
Development, 513-569-7631,
alvarez. franklin@epa.gov
Vapor
Compressor
Water Permeable
Membrane
Feed Liquid
Vapor
Stripping
Column
Make-up steam
Effluent
Ethanol-rich
Retentate
Vapor
Schematic diagram of energy
efficient Membrane Assisted Vapor
Stripping process for alcohol
recovery and dehydration.
U.S. Environmental Protection Agency
Office of Research and Development
Recycled/ recyclable
Printed witn vegetsWe-OasecJ ink or
paper lhal consists of a minimum of
50% pos1 consumer fiber contend
processed cnionne free
EPA600/F-11/018
June 2011
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