Environmental Engineering Reference
In-Depth Information
Results
pre-treatment (cellulase production), cellulose
hydrolysis (breaking apart sugar molecules), fer-
mentation, and distillation. The most critical step
in the process of determining which production
method to use is the cellulose hydrolysis. This
will be the step focused on for this production
process selection.
There are four different production methods
that will be discussed in this paper, including dilute
acid hydrolysis, concentrated acid hydrolysis, di-
rect microbial conversion, and enzyme hydrolysis.
Each of these production methods has positive
and negative aspects and will be analyzed as the
process pertains to an Oregon based cellulosic
ethanol company.
Examining the results of this evaluation, wheat
straw appears to be the preferable raw material
component for an Oregon based cellulosic etha-
nol supply chain. This is due to the fact that it is
widely available, at around two million dry tons
per year, and does not have a competing industrial
use. Of some concern is the feedrate of wheat
straw, since this is a seasonal crop, which will
need to be stored to support a constant supply of
raw materials for processing.
A close second option appears to be forestry
thinning. This raw material has the highest avail-
ability, at almost three million dry tons per year.
With competition from the paper industry however,
it is unlikely that much of this raw material can
be purchased at an economically cost effective
rate. The use of this raw material also requires
changes in public policy to allow a cellulosic
ethanol industry access to Oregon's forest lands.
Results for the other raw materials appear to be
very similar to one another. This suggests that any
of these remaining raw materials might be used
as supplementary raw materials, but are unlikely
to be the primary material used for a large-scale
Oregon based cellulosic ethanol industry.
Selection Criteria
When determining which production method to
use, it is important to systematically rank each
option against a set of criteria using the previously
discussed methodology. This criteria selection will
help to identify the most appropriate process for an
Oregon based cellulosic ethanol supply chain. The
selection criteria selected for the production pro-
cess are maturity of technology, cost of operation,
ethanol yield, and by-products / environmental
issues. Each of these criteria represents a critical
aspect of cellulosic ethanol production in Oregon
(Tables 8, 9 and 10).
Ethanol Production
Process Selection
The actual process of cellulosic ethanol produc-
tion when broken down to the fundamental steps
is simply the conversion of sugar molecules into
ethanol alcohol through fermentation. This process
has been used for centuries and is well understood.
The key step in this process is formation of sugar
molecules from cellulose within the plant mate-
rial, also known as hydrolysis. There are several
different types of biomass, as mentioned above,
and each may require unique features within the
individual steps. Regardless of which production
method is used, there are similar steps found in
Maturity of Technology (30 Points)
It is important for a start-up, or relatively new,
company to have a mature technology. Research
and development can be a time and capital in-
tensive process that has high risks. Unless the
company investors / owners have deep resources,
it is important for an Oregon based cellulosic
ethanol industry to select a production process
that has been relatively proven and is mature and
ready for production. This will increase the overall
probability of success and therefore it shall be
included in the selection process and will account
for 20 percent of the decision. (Table 8)
