Environmental Engineering Reference
In-Depth Information
6.5 Butanol and Other Chemicals
Once hemicelluloses and celluloses in biomass feedstock have been hydrolyzed,
the sugar “platform” can be utilized to generate a range of chemicals, including
other fuels such as butanol [59]. Butanol has several advantages over ethanol as an
alternative fuel (but not as an oxygenate) and may be a better choice for the large
volume liquid transport fuel market. However, if other chemicals are produced in
an ethanol plant, the final product separation process (distillation and dehydration)
would be problematical. Separate down-stream production paths will be required in
future biorefineries to accommodate the potential product flows, which may result
in different designs and configurations [15].
6.6 Heat (Lignin)
The main component remaining in the solid residues following cellulose and hemi-
cellulose hydrolysis to sugars is lignin (15-20% of the biomass feedstock) which
has a heating value just slightly less than coal (
28 GJ/ton for
coal). Therefore, lignin could be used as feedstock for co-firing, or gasification,
in an integrated biorefinery to generate heat and electricity. Lignin, and associ-
ated phenolic compounds, can also be used as chemical intermediates, however,
this market volume is probably limited. The main utilization will probably be for
heat and electricity: both for internal use in the biorefinery and perhaps to generate
surplus electricity that could be sold back to the grid, further capturing the economic
benefit [60].
∼
25 GJ/ton vs
∼
7 Current Outcome of Technological Implementation
7.1 Current Technology and Commercialization
For over 20 years, a considerable research effort has been made to overcome
the technical and economic barriers that currently limit the use of lignocellulosic
biomass. Most recently, the DOE has funded the development of several lignocel-
lulosic biofuel facilities that will help further define the parameters for potential
success. Some aspects of possible systems, such as concentrated acid hydrolysis,
dilute acid and steam explosion pretreatment, are relatively well understood at the
research level and will benefit from pilot-scale testing. Other aspects, such as fer-
mentation inhibitors and fermentation of C5/C6 sugars, require further research to
create sufficient improvements for commercial testing. Some technologies, such
as biomass gasification, syngas conversion to biofuels by either fermentation or
FT process, have been tested at a pilot scale and are ready for further scale-up
and integration testing. This is a crucial period of time for lignocellulosic biofuel
development: success with the current pilot scale operations will drive the required
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