BIOREFINERIES: INTEGRATION OF DIFFERENT TECHNOLOGIES - Biomass as a Sustainable Energy Source for the Future - page 498

Agriculture
(cultivation, harvesting,
deshelling)

Air emissions

Raw materials

Extraction and reining
(mechanical/chemical)

Wastewater

Energy, machinery
and infrastructure

By-products

Biodiesel production
(catalyzed transesteriication)

Seed cake

Auxiliary materials

Methanol
recovery

Separation and puriication

Jatropha biodiesel

FIGURE 15.8 Jatropha biodiesel generation, a generic scheme of processing.

production, since substantial soil capacity is required. However, as older
plants are able to sequester carbon, absorbing around 7.9 kg of CO 2 annu-
ally, Jatropha harvesting can serve purposes other than filling the looming
fuel gap. A study by Yale University has confirmed that renewable jet
fuel made from Jatropha oil can reduce greenhouse gas emissions by as
much as 91% (Bailis and Baka, 2010).
Oil extracted from the Jatropha has characteristics similar to fossil-based
diesel fuel. Due to this similarity, it can be used in most diesel engines, and
others can run on it with slight modifications (Nahar and Ozores-Hampton,
2011). The oil can be used directly in fuel combustion engines or may be sub-
jected to transesterification in order to produce biodiesel. In this example, we
will be taking this extra step to produce biodiesel.
The Jatropha oil is obtained by simply mechanically extracting it from the
seeds by using a screw press. In order to produce biodiesel, an esterification
process is used to produce the biofuel, which then only needs to be purified.
This process is shown in Figure 15.8, which also shows the extra ingredients
(left side) and by-products (right side) of this process.
Various processes can yield different rates of extraction; we choose high-efficiency
mechanical extraction, which is 91% efficient and uses 0.4 kWh

kg −1 (Nahar and
Ozores-Hampton, 2011). The seeds contain on an ar mass basis between 27 and
40% oil, with an average of 34% (Achten et al., 2007). The residue of the seed is
substantial and can be used in various industries including in our own process.