Environmental Engineering Reference
In-Depth Information
the information above in the production process
section.
After applying the criteria rankings as described
above, the data can be seen in Table 12.
The formula used to calculate the
Total
value
in Table 17 is as follows:
the ethanol plant, and the transportation options
may be limited.
Morrow, et al. (2006) modeled ethanol ship-
ping costs within the United Sates, and provided
estimates for pipeline, truck, and rail distribution
costs. Figure 13 shows the percentages of each
of these methods used for transporting petroleum
products. Unfortunately, ethanol cannot be shipped
in the same pipeline system with petroleum prod-
ucts due to ethanol's tendency to absorb moisture
and the presence of water in petroleum pipelines.
Even though “much of the existing petroleum
pipelines could be converted to ethanol transport
(Morrow et al., 2006),” until such time as ethanol
surpasses gasoline as the predominant transporta-
tion fuel, it is not unlikely that those pipelines will
be converted to ethanol, nor is it likely in the short
term that separate pipelines will be constructed
due to their high initial cost. Until a pipeline
is economically feasible, the main methods of
ethanol shipments will be truck, rail, and where
available, ships or barges.
Total=TechnologyMaturity×30+OperationalCos
t×35+Yield×25+ByProducts×10
Results
After evaluating the different ethanol production
methods it can be seen from the results in Table 12
that an Oregon based cellulosic ethanol industry
should adopt the Enzyme Hydrolysis production
method. This process has proven to be successful
and will continue to see significant cost savings
over other production methods. This production
method will only continue to improve as the
enzymes are designed and improved to generate
higher ethanol yield and produce little to no by-
products with minimal impact to the surrounding
environment.
The diluted acid hydrolysis method came in a
close second because it has also been proven and
has a lower operational cost then the concentrated
acid hydrolysis. The improvements in this method
by creating the two step process have significantly
increased the yield while simultaneously reducing
the by-products. This would be a logical method
to further investigate as a potential ethanol pro-
duction process.
Selection Criteria
Although cost is probably the number one crite-
ria for selecting the ethanol distribution method,
there are other criteria that ought to be considered
as well, such as the method's efficiency in us-
ing fossil fuels and its emissions of greenhouse
gases. The reason for considering these factors in
addition to cost is that the overall environmental
impact of a shipping method can negate some of
the environmental benefits of producing a fuel
from renewable resources. Availability, of course,
will often dictate the choice of transport, but it
may also be possible to combine, say truck and
barge to optimize shipping costs. A description
and relative weighting of each of these criteria
follows (Tables 13, 14, 15 and 16).
Ethanol Distribution Selection
Transportation costs for biomass are relatively
high due to their low density, so that the location
of an ethanol plant will be largely determined
by a local source of inexpensive cellulosic feed-
stock. Once the ethanol is produced, suppliers
must select an economical method to deliver it to
Availability (45 pts)
Clearly, if a transportation method is not available,
