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Encyclopedia of Physical Science and Technology EN002G-61 May 19, 2001 19:33

154 Biomass, Bioengineering of

B. Current Status of Biomass Processing is important and requires continuing attention. A key area
of agronomic research, particularly for large-scale energy
Biomass processing to industrial products based on starch,
crops, is to reduce the amounts of fertilizers, pesticides,
sugar, and oilseed raw materials is partially developed.
herbicides and other inputs required, both to minimize
Fiber crop processing to pulp and paper is very well de-
costs and to reduce potential environmental hazards.
veloped and is not discussed further here. Processing of
The second important area that is not directly process
lignocellulosic materials to industrial products other than
development is plant feedstock modification, either by
pulp and paper is very limited.
breeding or genetic modification. As mentioned, feed-
For processing of starch, sugar, and oilseed crops, a
stocks can be altered to make them easier to process, a
primary need is to develop additional industrial products
major advantage of biomass feedstocks compared with
from these raw materials. This is because a processing
petroleum raw materials. Feedstocks can also be altered to
infrastructure, or at least the beginnings of one, already
contain larger amounts of desirable components or even
exists or could be developed for each of these raw materi-
to contain entirely new components such as bioplastics.
als. Therefore the capital risk of a totally new plant is not
Careful integration of processing technology development
required. Corn wet and dry mills, sugar refineries for cane
and product recovery with feedstock modification is re-
and beet sugar, and oilseed crushing mills already exist
quired to achieve the maximum benefits of these genetic
and industrial products are already produced from these
manipulations. Presumably yields might also be affected
raw materials.
by some of these modifications. Thus feedstock modifi-
As additional products are developed and appear prof-
cation and yield enhancement should proceed as an inte-
itable, they can often be added to existing product lines at
grated whole.
existing facilities, for instance in a corn wet mill. Corn wet
millers have steadily increased the number and variety of
their products over the past two decades or so. This trend 2. New Technologies Needed for Low
is likely to continue. Growth of new biobased products at Cost Lignocellulose Conversion
oilseed crushing mills appears to have been much slower.
While it is relatively easy to convert starchy materials such
However, when circumstances appear favorable, totally
as corn to fermentable sugars and then to a variety of
new processing facilities can and will be built around spe-
fermentation products, lignocellulosic materials are much
cific new industrial products, as evidenced by the new
more difficult to convert to fermentable sugars. The poten-
plants for polylactic acid production announced and/or
tial benefit of economical conversion of lignocellulosics
under construction. Many of these starch or sugar-based
to fermentable sugars is the much larger possible volumes
products might also be produced at even lower cost from
and therefore lower costs of lignocellulose-derived sugars
inexpensive sugars generated in a lignocellulose conver-
compared to starch-derived sugars. Such low cost sug-
sion plant. Processing plants based on lignocellulose are
ars are a prerequisite to inexpensive fuel ethanol. Inex-
struggling to become established, at least partly because
pensive sugars could also significantly reduce the costs
the processing technology is underdeveloped and there-
of other biobased products such as polylactic acid or 1,3
fore relatively expensive compared to petroleum process-
propanediol.
ing technology.
Three primary areas for new technology development
are required to reduce the cost of producing fuel ethanol
C. Priorities for Developing and commodity chemicals from lignocellulosic materials:
Lignocellulose Biorefineries (1) an effective and economical pretreatment to unlock the
potentially fermentable sugars in lignocellulosic biomass
1. Enhancing Yield and Feedstock Modification
or alternative processes that enable more biomass carbon
The emphasis in this article on development of processing to be converted to ethanol or other desired products, (2)
technologies for large scale refining of lignocellulosic ma- inexpensive enzymes (called “cellulases”) to convert the
terials to industrial products is not intended to detract from sugar polymers in lignocellulose to fermentable sugars,
at least two other important development areas that are not and (3) microbes that can rapidly and completely convert
directly connected with processing technology. The first the variety of five and six carbon sugars in lignocellulose
of these is yield. The profitability of biomass conversion to ethanol and other oxygenated chemicals.
industries using dedicated (grown for that purpose) feed- Several lignocellulose pretreatment processes have re-
stocks will be strongly affected by the yield of raw material cently been developed that promise to be technically ef-
(tons of dry lignocellulosic material produced per year per fective and affordable, and some of them are undergoing
acre of land). Agronomic research to increase yields and large scale testing and development. Advanced lignocel-
develop improved plant varieties for biomass production lulose treatments include processing with ammonia and