Production of Synthetic Fuels and Chemicals from Biomass - Biomass Gasification, Pyrolysis and Torrefaction - page 401

Alternative sources of biodiesel are being researched. Instead of sugar beets
or rapeseed, cellulosic biomass like wood may be used as the feedstock.
With cellulosic materials, the industry can significantly increase the yield of
fuel per unit of cultivated area.
There are two options for production of ethanol or gasoline from nonfood
sources: thermal and biochemical.

11.5.4.1 Thermal Process
In the thermal process, cellulosic feedstock is subjected to fast pyrolysis (see
Chapter 5). The liquid produced is refined and upgraded to gasoline or etha-
nol. Since cellulose is the feedstock, the ethanol from it is often referred to
as cellulosic ethanol. An alternative thermal process involves gasification of
the biomass to produce syngas and synthesis of the syngas into diesel oil
using the FTS process. This process is described in Section 11.4.2 and is
illustrated in Figure 11.9 .

11.5.4.2 Biochemical Process
Figure 11.10 illustrates the biochemical process for production of ethanol
from nonfood lignocellulosic biomass. To produce alcohol, the long-chain
sugar molecules in the cellulose must be broken down into free sugar mole-
cules. Only then can the sugar be fermented into alcohol (ethanol), as in the
food-based process (refer to Figure 11.11 ). This extra step of breaking down

CO 2 compression

H 2

Biomass

CO 2 injection gas

H 2 Recovery

Fuel gas

Feedstock
processing
and drying

Syngas

COS
Hyd

Gasification
quench

Selexol FT

synthesis

Steam

Oxygen

AGT

Ash Shift

reaction

Air ASU

CO 2
removal

CO 2 compression

Product
recovery/
upgrading

Diesel

Naphtha

FIGURE 11.9 Transport fuel production from coal and biomass using FTS Source: Data from
White et al. (2007).