Environmental Engineering Reference
In-Depth Information
To what extent can petroleum be replaced, and by what alternatives, within the next
decades? While this potential is debatable, a realistic best-case scenario can be presented
given recent projections. In April, 2005, a report by the U.S. Department of Energy (DOE)
and the U.S. Department of Agriculture (USDA) estimated that the United States could quite
feasibly produce 1 billion dry tons of biomass feedstock (over half of which is waste) per
year, enough to displace 30 percent or more of the present U.S. petroleum consumption for
fuels and materials by 2030 [14]. When this is combined with projections of solar and wind
energy together providing 20 percent of the power demand in the industrialized world by that
time, it appears that biological resources could become important contributors to the
evolution of a post-petroleum world. Under these projections, CO2 emissions could peak
before 2050 and conventional fossil fuel use could be virtually eliminated by 2100 [6].
3. Unique Contributions from Biotechnology
The application of biotechnology to the production of commodities-notably fuels,
chemicals, and structural materials-increases the array of options available to supply
sustainable resources and preserve the environment. In particular, through the use of
biological feedstocks, biotechnology has the potential to minimize greatly the overwhelming
dependence developed countries, particularly the United States, have on petroleum and other
non-renewable fossil fuels for production of fuels and plastics.
Numerous mechanical, geothermal, and electrical technologies offer valuable
contributions to issues of energy independence and pollution prevention [15]. At the same
time, several unique advantages are brought by biofuels and bioproducts that will be
highlighted in this report.
First, many biotechnologies use the abundant, renewable, and potentially sustainably-
produced resource of plant biomass as the primary feedstock for liquid biofuels,
biochemicals, and biomaterials. Cellulosic and other biomass is currently available at the
commodity scale and is increasingly cost-competitive with petroleum, especially when
environmental costs are included, on both energy and mass bases [16]. Indeed, the land
resources of the United States are capable of producing a sustainable supply of biomass
sufficient to displace 30 percent or more of the country's present petroleum consumption,
amounting to approximately 1 billion dry tons of biomass feedstock per year [14].
Second, microbiotechnologies have the potential to use simple, organic, and inorganic
feedstocks in microbe-based bioreactors that generate desired products directly, without plant
biomass intermediates. For example, photosynthetic microbial biohydrogen production
requires only sunlight, CO2, salts, and water [17], and bioplastic precursors such as polylactic
acid and polyhydroxybutyrate can be made directly by microbes as well [18, 19].
Third, biotechnologies make use of enzymes, proteinaceous catalysts that are often
exquisitely selective and provide high rates of product generation. Unlike other catalysts,
enzymes can be manipulated genetically to improve parameters such as substrate affinity,
specificity, and catalytic rate, as well as tolerance to process conditions, longevity, and even
production rate of the enzyme itself by the host cell.
Finally, as a result of the above, many biotechnologies are able to avoid use of toxic
feedstocks and processing reagents that are necessitated by conventional methods and thereby
minimize toxic wastes. For example, biosynthesis of the denim dye, indigo, requires only
