Environmental Engineering Reference
In-Depth Information
Table 2.5
The potential of woody biomass produced in Thailand. (Laohalidanond et al.
2006
)
Source
Reside
LHV (kJ/kg)
Potential (kt/year) Potential (10˚KJ/
year)
Rubber wood
Saw mill
139,62
1373.44
19.18
Bark
2746.89
38.35
Eucalyptus
Saw mill
6,300
0
0
Bark
4649.25
29.29
Palm oil tree
Front
7,540
14355.86
108.24
In the first step the woody biomass material is transformed into syngas made
of water gas, at a temperature of 700-1,500
°
C. In the next step of Fischer Tropsch
process, the synthesis gas is cleaned of all impurities such as tar and catalyst poi-
soning substances. Once the gas is cleaned, it is converted into long chain hydro-
carbon product in the presence of high pressure and high temperature and iron or
cobalt based catalyst. Eventually these long chains of hydrocarbons are distilled,
upgraded and hydro cracked before being packaged as engine fuel (Laohalidanond
et al.
2006
)
In Japan, the automotive industry has also begun replacing gasoline with bio-
fuel diesel. Toshiaki 2010 explains in his bench scale experimentation the success-
ful manufacture of liquid fuel from woody biomass using the process of gasifica-
tion. The volume of the product made from biomass to liquid (BTL) plant is 1.9 L
of hydrocarbon liquid from 13 kg biomass of wood. The methodology of gasifica-
tion, cleaning and Fischer Tropsch are integrated. The gasification step leads to
oxygen enrichment, with the volume augmented from 21 to 31.5 %, leading to an
increase in the carbon conversion from 91 to 96 %. The use of 26.7 % of oxygen
as the gasifying agent results in a product containing 29 vol% of CO, 22 vol% of
H
2
, 11 vol% CO
2
, 2 vol% CH
4
and 35.5 vol% N
2
. COS and H
2
S concentrations are
decreased to less than 5 ppb in gas cleaning stage. Once the gas is cleaned, it is
compressed to 12.6 MPa to acquire the feed gas for the Fischer Tropsch production
(Hanaoka et al.
2007
).
Researchers in Medicinal Plant Cultivation Research Center Beijing, China have
shown that more amount of cellulose with less crystalinity, lignin and hemicellulose
can improve the yield of ethanol from woody biomass. Stupendous efforts have
been employed to achieve this by genetic modifications in the woody feedstock (Lu
et al.
2010
).
5
Third Generation Biofuels
5.1 Algae
Algae are a promising biofuel resource because of their ability to transform the
energy from the sun into chemical energy. The most important of all algae are the
microalgae. They are a possible foundation of renewable energy production such
