U.S. Department of Energy - Energy Efficiency and Renewable Energy

Biomass Program

Processing and Conversion

The Office of the Biomass Program focuses its research and development
efforts in converting biomass into fuels, products, and power via
two biochemical and thermochemical routes.

 

Biochemical Conversion - Biomass is broken down to sugars using either
enzymatic or chemical processes and then converted to ethanol via
fermentation.

Thermochemical Conversion - Biomass is broken down to intermediates
using heat and upgraded to fuels using a combination of heat and
pressure in the presence of catalysts. 

These R&D efforts focus on technologies and processes that can reduce
the cost and increase the efficiency of producing biofuels, products,
and power. Efficiencies can be achieved through methods for increasing
the yields derived from conversion of various feedstocks, among other
improvements. The majority of the Biomass Program's R&D is focused on
these technologies. Current R&D projects are described in detail in this
website's Information Resources section. 





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U.S. Department of Energy - Energy Efficiency and Renewable Energy

Biomass Program

Thermochemical Conversion

The Biomass Program conducts research on heat and pressure-based
conversion of various biomass feedstocks to alcohol and hydrocarbon
fuels, chemicals, and power. These conversion processes, including
gasification and pyrolysis, are described in detail in the links on the
left.

Thermochemical conversion is effectively applied to any biomass
feedstock.

Thermochemical processes also complement biochemical work by converting
lignin-rich non-fermentable material left over from high-starch
feedstocks conversion.

Thermochemical conversion will enhance fuel yields in integrated
biorefineries by combining conversion types with heat and power
efficiencies to produce fuel and products.

The Thermochemical Platform aims to efficiently produce biobased fuels
and co-products via the processes described on the left. The platform
aligns its R&D with the Program's goals according to the President's 20
in 10 initiative, which includes using stand-alone thermochemical
conversion, and integrating efficient, complementary thermochemical
conversion technology into a model biorefinery.

Feedstocks for thermochemical processes include a wide variety of
biomass types with little to no restrictions on physical or chemical
properties. Moisture and particle size are specified for the respective
conversion processes.





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U.S. Department of Energy - Energy Efficiency and Renewable Energy

Biomass Program

Biochemical Conversion

This area focuses on the research, development and demonstration of
biological processes that convert biomass to biofuels, chemicals, and
power. 

Biochemical processes also complement thermochemical conversion by
providing residual materials for further processing.

Biochemical conversion will advance in the future by enhancing fuel
yields in integrated biorefineries which combine conversion types with
heat and power efficiencies to produce fuel and products.

Lignocellulose (mainly lignin, cellulose and hemicellulose), is the
primary component of plant residues, woody materials and grasses. The
cell walls or these plant matters are comprised of long chains of sugars
(carbohydrates), which can be converted to biofuels. Biochemical
conversion breaks down the cell wall through the introduction of enzymes
or acid in order to extract the sugars which are then converted to
biofuels using microorganisms. Due to the complex structure of the cell
wall it is more difficult to break down into sugars, making this
material more expensive to convert to biofuels.

A key to developing cost-competitive cellulosic biofuels is reducing the
processing and capital cost and improving the efficiency of separating
and converting cellulosic biomass into fermentable sugars. Current R&D
focuses on high-yield feedstocks, more efficient enzymes, and more
robust microorganisms to advance biochemical conversion processes.





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U.S. Department of Energy - Energy Efficiency and Renewable Energy

Biomass Program

Thermochemical Conversion Processes

Gasification

In gasification conversion, lignocellulosic feedstocks such as wood and
forest products are broken down to synthesis gas, primarily carbon
monoxide and hydrogen, using heat. The feedstock is then partially
oxidized, or reformed with a gasifying agent (air, oxygen, or steam),
which produces synthesis gas (syngas). The makeup of syngas will vary
due to the different types of feedstocks, their moisture content, the
type of gasifier used, the gasification agent, and the temperature and
pressure in the gasifier.

 

Gas Cleanup and Conditioning

The syngas produced undergoes clean-up and conditioning to create a
contaminant-free gas having the appropriate hydrogen-carbon
monoxide ratio prior to the catalytic conversion step.

Among the contaminants removed during clean-up are tars, acid gas,
ammonia, alkali metals, and other particulates.

Syngas is then conditioned: hydrogen sulfide levels are reduced by
sulfur polishing, and hydrogen-carbon monoxide ratio is adjusted using
water-gas shift.

Pyrolysis

In pyrolysis processing, biomass feedstocks are broken down using heat
in the absence of oxygen, producing a biooil that can be further refined
to a hydrocarbon product. The decomposition occurs at lower temperatures
than gasification processes, and produces liquid oil instead of a
synthesis gas. Oil produced varies in oxygen content or viscosity
according to the feedstock used.

 

Bio-Oil Cleanup

Oil produced in pyrolysis processing must have particulates and ash
removed in filtration to create a homogenous product. The oil is then
upgraded to hydrocarbon fuels via hydrotreating and hydrocracking
processing, which reduces its total oxygen content.





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Content Last Updated: 04/08/2008

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