Biomedical Engineering Reference
In-Depth Information
generated, we know what to do; it is to get to that point using biomass
feedstocks that have received little attention. In the global push to
ferment plant starches to ethanol, little work has been done on biomass
gasification to methanol, the other alcohol.
When using biomass as a feedstock for biofuel production, there are
four basic production pathways: (1) biochemical conversion using
enzymes and microorganisms to breakdown biomass into sugars
used for fuel production; (2) thermochemical conversion employing
heat energy and chemical catalysts to convert biomass into fuels; (3)
gasification to dissociate biomass in a high-temperature, oxygen-
starved environment to produce synthesis gas; and (4) pyrolysis using
high temperatures in an oxygen-free environment to encourage the
decomposition of biomass. As the simplest alcohol, methanol can be
produced from virtually any organic material using some form of these
processes. However, the most common methods employed to produce
methanol from biomass involve the gasification of “dry biomass”
(forest thinnings, waste wood, pulp mill byproducts, municipal solid
waste) and the fermentation of “wet” biomass (animal manure, waste-
water, industrial wastewater, algae, seaweed) typically through anaero-
bic digestion (Specht and Bandi).
Biomass gasification for methanol production is especially attract-
ive as high carbon conversion rates and fuel yields mean that the
biomass resource can be completely utilized. By comparison, con-
ventional production processes for the biochemical conversion of
plant starch and oil plants use only a small fraction of the biomass
feedstock. For example, it is understood that production of ethanol
from corn yields 7.2 dry tons/ha/year, or 76 GJ/ha/year, whereas the
production of methanol from wood yields 15 dry tons/ha/year or the
equivalent of 177 GJ/ha/year (Williams et al., 1995). In other words,
through gasification, 1 ton of woody biomass can produce 165 gallons
of methanol while the hoped for yields for cellulosic ethanol is
targeted to around 60-70 gallons of fuel per ton of biomass. As
the Swedish Minister for Enterprise and Energy Deputy Prime Min-
ister Maud Olofsson put it, “We need to move away from first
generation in ethanol manufacturing and further to second and third
generation, which is all about cellulose material and gasification, and
