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142 Biomass, Bioengineering of

a cost per unit of energy basis. Although the biomass II. CHARACTERISTICS OF BIOMASS
resource is huge and comparatively inexpensive, we have
invested much less effort in learning how to bioprocess A. Production of Biomass
or convert it efficiently to biobased industrial products
1. Natural Inputs to Biomass Production
than we have invested in converting petroleum to meet
our needs for fuels, chemicals, materials, and other indus- Natural (or ecosystem) inputs to biomass production are
trial products. soil (including the associated nutrients and living organ-
Compared to the petroleum processing industry, the isms found in soil), genetic information, air, water, and
biomass processing industry is still relatively under- sunlight. All of these inputs are potentially renewable in-
developed, although the biomass processing industry is definitely with proper oversight and intelligent design. In
in fact already very large and is also growing rapidly. fact, biomass production has the potential to improve soil,
Thus much of this article deals with what is required for water, and air quality. The entire life cycle of biomass
the biomass processing industry to grow further and what production, bioprocessing, and biobased product use and
some of the possible and desirable growth paths for this disposal should be examined carefully to discover and
industry might be. properly exploit such opportunities. Intelligent design of
biomass processing systems should take advantage of
opportunities to improve the environment and enhance
ecosystem stability under circumstances peculiar to each
I. BACKGROUND region and product. With careful and thoughtful design,
biomass production and processing can increase or en-
The potential benefits (including economic, environmen- hance the “natural capital” of soil, air, and clean water
tal and national security benefits) of obtaining a larger upon which all life depends.
fraction of our fuel and chemical needs from biomass Human inputs to biomass production include additional
rather than from petroleum have driven increasing inter- plant nutrients beyond those provided through the ecosys-
est in biobased industrial products in the United States and tem, plant genetic improvement, labor, financial capital
many other countries. Lack of cost–effective bioprocess- and intelligence, as referred to above. Much agriculture is
ing technology is perhaps the principal barrier to more also practiced with large inputs of fossil fuels. As men-
economical production of biobased industrial products. tioned, thorough and careful life cycle analysis is required
Although biomass is abundant and low cost, unless we to determine whether biomass processing to biobased
learn how to cost-effectively convert biomass to these in- products actually fulfils its potential to give us a more
dustrial products, their potential benefits will be largely sustainable economy.
unrealized.
While the potential benefits of biobased products are
2. Potential and Actual Yields of Biomass
certainly real, it is also correct that unless such products
are produced with proper intelligence and care, their ben- A key factor determining the economic (and therefore the
efits may be reduced or even negated. We must be careful resulting ecological) benefits of biomass production and
that biomass is grown, harvested, converted to industrial processing is the yield of biomass, defined as the annual
products, and that these products are used and disposed production of biomass (dry weight) per unit land area, of-
of, in sustainable, environmentally sound systems. Care- ten expressed as tons of dry biomass per acre per year.
ful, thorough and easily verified life cycle analyses will Meeting legitimate human needs by more intensively pro-
help us realize the potential of biobased industrial prod- ducing biomass (i.e., increasing yields) will allow larger
ucts to benefit our economy and our environment and also tracts of land to be set aside for recreation, parks, and bi-
to avoid potential problems with the production and use ological reserves. Biomass yields vary widely. The upper
of these products. limit of solar energy conversion efficiency by biomass ap-
One of the most important areas demanding careful life pears to be about 12% (incoming solar energy converted
cycle (whole system) attention for biomass conversion to to the energy content of plant material). Yield seems to be
industrial products is the potential conflict with food and tiedcloselytoconversionefficiency;thehighertheconver-
feed production. Biomass production for biobased indus- sionefficiency,thehighertheyield.Sugarcaneisoneofthe
trial products seems to conflict with use of the same agri- more efficient crops, with solar energy capture efficiencies
cultural resources for human food and animal feed. This in the neighborhood of 2 to 3% and corresponding biomass
article briefly addresses this crucial point and finds con- yields of between 25 and 35 dry tons per acre per year. The
siderable room for optimism. corresponding efficiency value for corn is about 0.8%.