Applications of Lignocellulose Biotechnology in Bioenergy - Biotechnology of Lignocellulose - page 213

Fig. 6.1 Continuous fermentation device for biomass synthesis gas to generate alcohol [ 3 ]

6.2.1.2 Thermochemical Conversion

In thermochemical conversion, lignocellulose is first thermochemically gasified to
generate synthesis gas, and then synthesis gas is changed into ethanol by a biological
or chemical catalytic method.
There are two ethanol production processes that currently employ thermochem-
ical reactions. The first system is actually a hybrid thermochemical and biological
system. Lignocellulosic biomass materials are first thermochemically gasified, and
the synthesis gas (a mixture of hydrogen and carbon monoxide) is bubbled through
specially designed fermentors. A microorganism that is capable of converting the
synthesis gas is introduced into the fermentors under specific process conditions
to cause fermentation to bioethanol at last [ 14 , 18 ]. Datar used switchgrass as a
raw material. First, the fluidized bed gasifier generated gas with a composition of
56.8 % N 2 , 14.7 % CO, 16.5 % CO 2 ,4.4%H 2 , and 4.2 % CH 4 under 750-800 ı C.
Then, the producer gas was utilized in a bioreactor to generate ethanol and other
products via fermentation using P7 clostridial bacterium under 37 ı C and absolute
anaerobic conditions [ 3 , 19 ]. The process is presented in Fig. 6.1 .
The second thermochemical ethanol production process does not use any
microorganisms. In this process, biomass materials are first thermochemically
gasified, and the synthesis gas is passed through a reactor containing catalysts,
which causes the gas to be converted into ethanol [ 14 , 20 ]. Phillips used the second
method to produce ethanol: First, biomass was treated in the absence of oxygen
at a high temperature (600-1,000 ı C) to produce mixed cracked gas, of which the