Environmental Engineering Reference
In-Depth Information
from the wood used for conversion to ethanol fuel is industrially known as wood
diesel. Wood biomass may be regarded as a second generation biofuel but it is not
a new candidate to human understanding and awareness. It was in 1819 when a sci-
entist discovered that the addition of concentrated acid solution to cellulose present
in wood can be dissolved to yield sugar; a precursor for production of ethanol. This
process of dissolving cellulose in dilute acidic solution began contributing to the
production of ethanol in Germany during World War I and II. From then onwards
wood hydrolysis is being used in many developed countries (Lynd et al.
2005
). For
numerous decades biofuels from wood were not very economical. Over the years,
as the demand for energy sources and environment friendly fuels aggravated, a few
of the developed countries began working on modifying methods for processing
engine fuel from wood at an opposite cost scale.
4.3.1
Production of Lipid Fuel via Gasification of Woody Mass
The most significant lipid fuels, definitely obtained from wood are ethanol, metha-
nol and diesel fuel. Other potential candidates on which studies are yet to be con-
ducted include mixed alcohols, tert-amylmethylether, tert-butyl alcohol, iso-propyl
alcohol and sec-butyl alcohol. The main contents vital for qualifying wood as sourc-
es of bio-diesel are basically: cellulose, lignin and hemicellulose. The distribution
of each of these contents varies according to the species (Pauly and Keegstra
2010
).
For instance there is 45 % cellulose, 20 % lignin and 30 % hemicellulose in Angio-
sperm wood. The distribution of contents in gymnosperm wood is crudely 42, 27
and 28 % cellulose, hemicellulose and lignin respectively (Singh et al.
2010
). The
decomposition of wood is distributed mainly into three categories: pretreatment,
hydrolysis of cellulose into sugar and fermentation of sugar to give alcohol. The
pretreatment step is essential for the proper function of the second step, because
in the pretreatment step, the lignocellulosic matrix is disrupted to provide easy ac-
cess for the enzymes or chemicals to cellulose (Mosier et al.
2005
). Recently, many
developed as well as developing countries have begun taking greater interest in gas-
ification of woody biomass for a successful alternative to fossil fuel biofuels, chief
among them are countries like Thailand, Japan and USA. In the countries where the
industrial and the transportation sector is developing at an astounding rate, the fossil
fuel derived energy resources are depleting, leading to an oil crisis.
Thailand is a tropical country with a large percentage of area covered by for-
ests and lakes. There are three types of wood in Thailand as will be clear from
Table
2.5
, which can be and are considered as wood fuel, namely, rubber wood,
palm oil tree and eucalyptus. The woody biomasses from these plants are separated
into bark from saw mills followed by wood processing (Laohalidanond et al.
2006
).
Transportation fuel is processed by two ways in Thailand. One is transesterification
and the other is fermentation. Similar to production of bio-ethanol, wood diesel is
also manufactured via biomass gasification through the Fischer Tropsch synthesis
process (BG-FT). The BG-FT process has three steps (Laohalidanond et al.
2006
):
Biomass Gasification
,
Gas cleaning
,
Fischer Tropsch Process.
