Environmental Engineering Reference
In-Depth Information
(4CL) was downregulated by antisense inhibition, exhibited up to a 45% reduction of lignin and it
was further compensated for by a 15% increase in cellulose (Hu et al. 1999).
27.5.2 S
uStainaBlE
a
griculturE
and
E
nErgy
c
ropS
Defining agricultural sustainability is subjective, but extractive agricultural practices are always
ecologically unsound. The “highest use” for a farm's land must take into account the farm's
economics, the environment of which it is a part, and the social value of enabling people to
live on the land. The long-term view is important (e.g., for soil productivity and minimization
of “boom and bust” economic fluctuations). Woody biomass can give farmers flexibility in
fluctuating economic conditions and help to keep farms profitable and intact. Biomass crops
can be planted on marginal lands that require vegetative cover for critical periods or that would
otherwise provide very little or no income without significant ecological damage. To be profitable,
the amount of energy that the biomass fuel provides must exceed that used to produce it. Harvest
must be timed to protect important wildlife species. Leaving residues on the field and a root
system in the soil will protect against soil erosion and preserve soil structure. A market and cash
flow must be guaranteed to reduce the risk for the farmer and provide the profitability needed to
think long-term.
Optimizing cellulose processing by refining biomass pretreatment and converting crop residues,
first-generation energy crops, and other sources to liquid fuels will be the immediate focus. This will
entail reducing cost, enhancing feedstock deconstruction, improving enzyme action and stability,
and developing fermentation technologies to more efficiently use sugars resulting from cellulose
breakdown. One goal is to decrease industrial risk from a first-of-a-kind technology, allowing more
rapid deployment of improved methods. To achieve higher production goals, new energy crops with
greater yield per acre and improved processibility are needed.
27.5.3 B
iomaSS
p
roduction
p
otEntial
of
p
aulownia
The term “biomass” in the present context as a bioenergy feedstock is intended to refer to materials
that do not directly go into foods or consumer products but may have alternative industrial uses.
Common sources of biomass are (1) agricultural wastes, such as corn stalks, straw, seed hulls,
sugarcane leavings, bagasse, nutshells, and manure from cattle, poultry, and hogs; (2) wood
materials, such as wood or bark, sawdust, timber slash, and mill scrap; (3) municipal waste, such as
waste paper and yard clippings; and (4) energy crops, such as poplars, willows, switchgrass, alfalfa,
prairie bluestem, corn (starch), and soybean (oil).
27.5.4 l
lignocElluloSic
B
iofuEl
and
p
aulownia
Paulownia is one of the fastest-growing tree species capable of generating a large amount of biomass
in a short period of time (~70-80 lb/tree per year in the first year and ~200 lb/tree per year from the
second year onward; unpublished data from WPI), and it can be grown and harvested seasonally
or annually in many states of the United States. Research conducted at WPI suggests that up to
68 wet tons of fiber per acre per year can be produced by establishing a Paulownia farm.
All of our
current micropropagation field trials for biomass yields at different spacing
at the Fort Valley State
University are being conducted on
P. elongata
.
Environmental concerns regarding the use of fossil fuels and production of carbon dioxide, coupled
with increased energy costs, fostered the expansion of the fuel ethanol industry. The industry has
become an important partner with U.S. agriculture. The U.S. Department of Agriculture estimates
that 17,000 jobs are created for every billion gallons of ethanol produced. The most recent thrust
in the United States has been the construction of new corn-based ethanol production facilities.
Over the last decade, technology has improved and refined the process of conversion of grains
