Page 31 - Academic Press Encyclopedia of Physical Science and Technology 3rd BioTechnology

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

156 Biomass, Bioengineering of

produce electricity, although there are several other sus- products, done with reasonable care, should not have en-
tainable sources of electricity. Biomass is also uniquely a vironmental impacts more severe than the corresponding
source of human food and animal feed. petroleum-derived products. In fact, biobased products are
Because biomass production is widely dispersed geo- well suited to composting or other resource recovery ap-
graphically, biobased industrial products can potentially proaches that return their constituent atoms to the global
form the basis of both local and worldwide economic sys- cycles of materials.
tems that are much more equitable and balanced. Also
becausebiomassproductioniswidelydispersed,resource-
C. Achieving the Benefits
driven international conflicts over petroleum might be
of Biobased Products
minimized or avoided entirely.
Biomass production is a key part of global cycles of While the potential benefits of biobased products are cer-
carbon, oxygen, nitrogen, water and other compounds. If tainly real, so are their limitations and possible problems.
we intelligently produce and use biobased industrial prod- One way of achieving the benefits of biomass processing
ucts we may actually improve environmental quality and to biobased products is to do careful, system-level studies
increase or enhance the stocks of “natural capital” such as of specific products in order to anticipate and resolve po-
soil, water and air upon which all life depends. Numerous tential problems before large industries are launched and
opportunities also exist to integrate biomass production the damage is done. Life cycle analysis is suited to such
andprocessingwithwasteutilizationandrecoveryofdam- system studies. For example, there is an obvious potential
aged or less fertile lands. For example, the organic fraction for biomass production for biobased products to conflict
of municipal solid wastes might be combined with human with food production. Careful studies are required to an-
and animal wastes and composted to enrich marginal soils ticipate and resolve such conflicts before they occur.
producing perennial grasses for a bioethanol facility. Fur- One potential resolution of this apparent conflict with
thermore, since plants fix atmospheric carbon both in their food and fuel production is to coproduce foods and animal
above and below ground parts, the potential exists to con- feeds with fuel and chemical production from biomass.
tinue to use petroleum and other fossil fuels indefinitely, Most biomass produced is actually fed to animals, rather
balancing the amount of atmospheric carbon dioxide liber- than directly to humans. Since most biomass also contains
ated by fossil fuel combustion with the uptake and fixation protein (required in all animal diets), the potential exists
of carbon dioxide by plants. to recover this biomass protein in a biorefinery and use
it to feed animals, or perhaps even people. Assuming an
average protein content of 10% in grasses and residues,
B. Potential Limitations of Biomass
and assuming 80% recovery of this protein in biorefineries
and Biobased Industrial Products
also producing ethanol fuel, about 1 billion tons of grass
Perhaps the most serious potential limitation of biomass would be required to replace all of the protein currently
and biobased industrial products is the possible conflict produced worldwide as high protein meals from oilseeds
with food and feed production on the same land. While such as soybeans. The equivalent amount of ethanol
biomass utilization for organic chemicals and materials, produced would be about 100 billion gallons per year,
done properly, is not likely to result in conflicts with food about half of the U.S. demand for liquid transportation
production, biomass production and utilization for liquid fuels.
fuels such as ethanol might indeed conflict with food pro- Similarly, the calories (food energy) in lignocellulosic
duction. This is particularly true if fuel use efficiency does materials are not very available for animal digestion and
not increase dramatically over the time frame that biofuels they are essentially useless in human nutrition. However, if
are implemented. Food production will always be a higher the technical roadblock of lignocellulose pretreatment for
human priority than production of fuels or plastics. This production of fuels is resolved, it will also be resolved for
issue must be carefully considered and appropriate reso- pretreatment to increase the food and feed calories avail-
lutions achieved if biobased industrial products, including able from lignocellulosics. For example, ruminant animals
biomass-derived liquid transportation fuels, are to provide typically digest less than half of the calories potentially
us their full social, economic and environmental benefits. available in grasses. If pretreatments make those calories
Some threats to biodiversity and water and soil qual- 90% percent available both for fermentation to ethanol and
ity are also possible from greatly increased levels of also for animal feeding, then the treatment of about 4 bil-
biobased industrial products. Erosion and increased con- liontonsperyearofgrasseswillmakeavailableforfeed(or
tamination of soil and water with fertilizers, pesticides food) and fuel uses new, additional calories approximately
and herbicides might result from intensive production equal to the calories contained in the entire world grain
of biomass for biobased products. Disposal of biobased crop of about two billion tons per year. Thus while both