Page 305 - Advances in Eco-Fuels for a Sustainable Environment

262 Advances in Eco-Fuels for a Sustainable Environment

biorefinery concept, hybrid technologies from various fields, including agriculture,
chemistry, engineering, and microbiology, are applied to an integrated process to sep-
arate biomass into its building blocks, such as carbohydrates, proteins, and oils. These
compounds can be further converted to other value-added products such as platform
chemicals, energy, and biofuels.
Compared to obtaining a sole product with conventional processing, biorefinery
processing of agriculture waste to produce multiple value-added products has several
significant advantages, such as full utilization of feedstocks, thus minimizing waste
generation during processing, diversification of the revenues by covering multiple
markets/niches, synergy effects of different technologies, sharing manpower and
equipment, and potential achievements of energy self-efficiency via biogas produc-
tion or inert fiber material burning. Therefore, during the past 10years, research
focused on integrated utilization of plant-derived waste to produce various products
has flourished.
In general, a biorefinery can be divided into three phases (phase I, phase II, and
phase III) regarding biomass, targeted products, and processes used [111]. In phase
I, a biorefinery has little flexibility during the whole process, and it normally uses
one type of biomass and one process to produce one targeted product. In a phase II
biorefinery, more products can be produced during the process. A phase III biorefinery
has an even higher flexibility than a phase II biorefinery. It is not only able to produce
multiple value-added products, but also use different types of feedstocks and
processing methods. Therefore, a phase III biorefinery can ensure a stable supply
for the process during the whole year and improve the economic feasibility of agri-
culture waste valorization.
In a biorefinery design, there are three key points that should be considered: bio-
mass feedstock, final produc,t and route (technologies). Rice bran as a byproduct of
rice milling has the potential as a biorefinery raw material with the valorization of
nonedible fractions (lignin, cellulose, and hemicellulose) for the synthesis of platform
molecules for chemicals, energy, fuels, and materials. This is similar to other ligno-
cellulosic feedstocks but also with the recovery of minor compounds with high-added
value that can be economically very beneficial for the biorefinery process. The com-
position of rice bran is shown in Table 9.9.
It is well known that acid-catalyzed alcoholysis of glycerides is a slow process and
the rate of methanolysis and the final fatty acid methyl ester (FAME) content in the
product depend on the initial FFA content in the RBO. Therefore, a substantial amount
of unreacted glycerides was still detected even after 24h of reaction time if the starting
RBO contains more than 20% of FFA [6]. Dewaxed/degummed RBO with FFA con-
tents of 24.5% and 49.5%, respectively were used as the feedstock in acid-catalyzed
methanolysis at atmospheric pressure, T¼ 100°C, molar ratio oil/methanol of 1/10 and
2 wt% of sulfuric acid used as catalyst for 24 h of reaction time, the FAME content in
the product were 62% and 73%, respectively [6]. With noncatalytic in situ
trans(esterification) of rice bran (initial FFA content of 37.6%) using a subcritical
water-methanol mixture under optimum conditions (T ¼200°C, P ¼4MPa under
CO 2 atmosphere, 3h reaction time, and 43.8wt% methanol), 100% oil in the bran
can be recovered and 66.1% FAME content can be achieved [4]. Complex