Biomedical Engineering Reference
In-Depth Information
hydrogenolysis, carboxylation, catalytic dehydration, pyrolysis, and gasifica-
tion, many value-added chemicals can be produced from glycerol.
11.5 TRANSPORT FUELS FROM BIOMASS
Biodiesel, ethanol, and biogas are transport fuels produced from biomass that
are used in the transportation industry. The composition of biodiesel and bio-
gas may not be exactly the same as their equivalence from petroleum, but
they perform the same task. Ethanol derived from biomass is either used as
the sole fuel or mixed with gasoline in spark-ignition engines.
Two thermochemical routes are available for the production of diesel and
gasoline from syngas:
1. Gasoline, through the methanol-to-gasoline (MTG) process.
2. Diesel, through the FTS process.
Similarly, there are two biochemical means for the production of ethanol
and diesel:
Diesel, through the transesterification of fatty acids.
Ethanol, through the fermentation of sugar.
It may be noted that in both schemes, part of the syngas's energy content
(30
50%) is lost during conversion into liquid transport fuel. It is apparent
from
Table 11.4
that this loss in conversion from biomass to methanol or
ethanol can be as high as 50%, and further loss can occur when the methanol
is converted into a transport fuel like gasoline. For this reason, when we con-
sider the overall energy conversion efficiency of a car, running on biogas,
and compare it with that of an electric car, the former shows a rather low
fuel-to-wheel energy ratio.
11.5.1 Biochemical Ethanol Production
Ethanol is the most extensively used biofuel in the transportation industry.
Ethanol can be mixed with gasoline (petroleum) or used alone for operating
spark-ignition engines, just as biodiesel can be mixed with petrodiesel for
TABLE 11.4
Energy Losses in Methanol Production
Conversion Process
Energy Loss (%)
Biomass to methanol
30
47
Coal to methanol
41
75
Source: Data compiled from Reed (2002), p. III-226.
Search WWH ::
Custom Search