Environmental Engineering Reference
In-Depth Information
to prepare the raw material for transportation, but
does not include actual transportation from col-
lection site to processing plant. Collection costs
directly affect the profitability of a cellulosic
ethanol supply chain, but can also be very much
affected by governmental policy such as subsi-
dies, tax breaks, etc. For this reason collection is
weighted at ten points (Table 6).
ing cellulosic ethanol industry (Biotechnology
Industry Organization, n.d.).
Agricultural residues represent a significant
cellulosic feedstock available in Oregon as well.
According to an Oregon based study, “agricultural
residues account for over 4 million bdt [bone dry
tons] per year of potential feedstock for ethanol
production.” (Graf and Koehler, 2000). Unlike
many other states however, the predominant
cellulosic feedstock in Oregon is wheat straw.
Numbers provided by Pacific Ethanol (Davis,
2008a) for Franklin and Walla Walla counties
show 41,200 available tons of corn stover versus
348,200 available tons of wheat straw. In the state
of Oregon there are over 2 million tons of wheat
straw produced every year. Wheat straw has an
excellent conversion ratio at 60 gallons of ethanol
per dry ton. The potential ethanol production from
wheat straw alone is “roughly 90 million gallons
of ethanol per year” (Graf and Koehler, 2000) once
sustainability practices are taken into account.
Another agricultural residue available in Or-
egon is grass seed straw. Oregon is the world's
leading producer of grass seed, producing around
1 million tons of grass seed straw annually. Half
of this grass seed straw is exported as feed, while
the remaining half is disposed of through burning
or chopping. Like wheat straw, grass seed straw
has an excellent conversion ratio at 60 gallons
of ethanol per dry ton (Graf and Koehler, 2000).
In Oregon most agricultural residues are either
burned or tilled back into the soil. The sale of these
residues as cellulosic feedstocks can create addi-
tional economic value for farmers. Pacific Ethanol
(Davis, 2008a) estimates farmer compensation for
cellulosic feedstocks to be somewhere around $15
per ton, after accounting for the cost of chopping,
raking, and baling. The collection and use of these
agricultural residues has no impact on the growth
of food crops as long as a sufficient amount is
tilled back into the soil for conservation purposes
(Graf and Koehler, 2000).
Competition (30 pts)
Competition is defined as the potential for indus-
tries that have competing uses for a particular raw
material. These industries can drive up the cost
of a raw material if they are willing to pay higher
prices to acquire the material. Competition can
make a raw material too expensive to be used
economically in a cellulosic supply chain. For
this reason competition is very important and
weighted at thirty points (Table 7).
Raw Materials Available
Agricultural Residues
A joint study between the USDA and DOE esti-
mates the total annual amount of available feed-
stock from agricultural sources in the United States
to be somewhere around 1 billion dry tons. The
majority of this feedstock comes from agricultural
residues, which are the biomass left on farmland
after harvesting. Examples of agricultural residues
useful as cellulosic feedstocks are corn stover and
wheat straw. The joint study came to the conclu-
sion that “428 million dry tons of crop residues
could be available on an annual basis by 2030.”
(Biotechnology Industry Organization, n.d.).
Of all the sources of agricultural residue avail-
able in the United States, corn stover is by far the
most predominant. Agricultural lands annually
produce 75 million dry tons of corn stover, with
the next closest feedstock being wheat straw at
only 11 million dry tons. The amount of corn
stover currently available in the United States
makes it an excellent feedstock for the emerg-
