Page 79 - Biofuels Refining and Performance

62 Chapter Two

There has been a tremendous increase in biobased products such as
ethanol, high-fructose syrups, citric acid, monosodium glutamate,
lysine, enzymes, and specialty chemicals worldwide. It is estimated
that in 2000–2006 in United States alone, there will be an increase
in the use of liquid fuels, organic chemicals, and biopolymers from the
current level of ~2%, 10%, and 90% each to 10%, 25%, and 95%, respec-
tively [19].

2.6.1 Gaseous products
In Chap. 1, gasification (pyrolysis) of biomass, biogas, gobargas, hydro-
gen, and biohydrogen were discussed in detail.

2.6.2 Liquid products
An important renewable energy resource for transportation purposes is
liquid fuel based on plant oils. However, pure plant oils are generally
not suitable for use in modern diesel engines. This can be overcome by
the process of transesterification. The resultant fatty-acid methyl esters
have properties similar to those of diesel and are commonly called
biodiesel. Biodiesel presents several advantages, such as better CO 2
balance than diesel, low soot content, reduced hydrocarbon emissions,
and low carcinogenic potential [20]. The specification standards for the
European Union (EU) and the United States are EN14214 and ASTM
D6751, respectively. The EU directive established a minimum content
of 2% and 5.75% biodiesel for all petrol and diesel used in transport by
December 31, 2005, and December 31, 2010, respectively. Biodiesel
refers to the pure oil before blending with diesel fuel. Biodiesel blends
are represented as “BXX,” with “XX” representing the percentage of
biodiesel component in the blend (National Biodiesel Board, 2005) [21].
In the biomass-to-liquid conversion processes, biomass is broken down
into a gaseous constituent and a solid constituent by low-temperature
gasification. The next step involves production of synthetic gas, which
is converted into fuel (termed SunFuel) by the Fischer-Tropsch synthe-
sis process, with downstream fuel optimization by hydrogen after treat-
ment [22]. Ethanol has already been introduced in countries such as
Brazil, the United States, and some European countries. In Brazil, it is
currently produced from sugar and, in the United States, from starch
at competitive prices. Ethanol is currently produced from sugarcane
and starch-containing materials, where the conversion of starch to
ethanol includes a liquefaction step (to make the starch soluble) and a
hydrolysis step (to produce glucose). There are generally two types of
processes for production of bioethanol: the lignocellulosic process and the
starch process. Unlike the starch-based process, the lignocellulosic
process has not been as widely adopted due to techno-economic reasons.