Partnerships, Future, and Emerging Technologies - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 415

Thermal Routes
Thermal routes can be categorized onto three areas based on the intermediate they
produce, liquefaction, pyrolysis, or gasification. Figure 19.5 shows the intermediate
as a function of severity of deconstruction.
The highest severity thermal deconstruction technique is gasification at temper-
atures of 600 C and above, depending on the type of gasification technology used
[ 52 ]. Once a syngas has been produced and appropriately cleaned and conditioned,
there is a multitude of fuel synthesis routes for producing an advanced biofuels
[ 53 ]. Some of these routes such as Fischer-Tropsch synthesis are well-proven
technologies that are being practiced commercially in certain countries such as
South Africa. Others are more in the development stage such as single-step olefinic
gasoline production that shows better potential for being economically viable at the
scale of biomass.
The mid-severity thermal deconstruction technique is pyrolysis which is
performed at temperatures in the range of 300-600 C[ 54 ] at atmospheric pressure.
Pyrolysis processes produce oil commonly referred to as “bio-oil” or “pyoil” that
somewhat resembles crude oil in appearance but has dramatically different physical
and chemical properties. The initial biomass pyrolysis process developed was fast
pyrolysis. This process is well proven and relatively efficient, but the oil produced
has some very undesirable properties that present some significant challenges for
upgrading to advanced biofuels [ 55 ]. Many of these desirable properties are directly
related to the high oxygen content of the bio-oil.
Fig. 19.5 Thermal intermediate as a function of temperature and residence time