Biodiesel From Conventional Feedstocks - Biotechnology in China: Biofuels and Bioenergy - page 57

Taking Jatropha curcas L. as an example, it is widely distributed from dry
subtropical regions to tropical rain forests. Its current production is mainly in
Guangdong, Guangxi, Yunnan, Sichuan, Guizhou, Taiwan, Fujian, and Hainan
Provinces. Other tropical and subtropical regions are also potentially suitable for the
plant to grow. Scientists from Sichuan University and Southwest Forestry Institute
are the main players in J. curcas research and planting, investigating how to increase
the output of the plant seed as well as process the seed oil for biodiesel production.
Since 2003, Guizhou Province has been collaborating with Germany's Daimler
Chrysler in the development of large-scale liquid biofuel production from J. curcas
seed, which aims at improving the barren area by building up ecological protective
systems and promoting rural economic development through sustainable agricul-
tural production, which can improve farmers' income and reduce their migration.
The seed yield of Jatropha curcas can approach to 9.75 ton/ha with 40% oil
based on dry mass. Economic benefits can be further enhanced by the refining of
the feedstock with by-products such as value-added insecticide from the dregs and
fertilizer from the remaining residues [ 8 ]. Currently, the seed of J. curcas is mainly
imported from Thailand and India, but China is developing the cultivars from local
Jatropha varieties. Although J. curcas. is promising as a feedstock for large-scale
biodiesel production, other factors such as the high labor cost of harvesting the
plant seed need to be taken into consideration.
3 Current Technologies for Biodiesel Production
The transesterification reaction is the core of biodiesel production, and refers to
the formation of fatty acid alkyl-ester (mainly methyl ester or ethyl ester) by the
reaction between triglycerides and methanol or ethanol with or without a catalyst.
Various vegetable oils and animal fats as well as waste oils can be used as
the raw materials for the transesterification reaction to produce biodiesel. After
the transesterification reaction, the molecular weight of natural grease falls to
one-third of the original. Although short chain alcohols, such as methanol or
ethanol, can be used for the transesterification reaction, methanol is most widely
used because of its low price, short carbon chain, strong polarity, and fast reaction
rate. The transesterification reaction can occur with the use of acid, alkali, or
enzyme as catalysts, or in a supercritical fluid system without catalyst.
3.1 Homogeneous Catalyst-Mediated Process
3.1.1 Homogeneous Alkali-Catalyzed Reaction
Homogeneous alkali-mediated biodiesel production is a mature technology
with wide applications in the USA and Europe. Commonly used alkali catalysts
include sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium