Environmental Engineering Reference
In-Depth Information
Biodiesel from Used Vegetable Oils (UVO) and Fats
UVO and animal fats are also considered as very attractive feedstocks for the
production of biodiesel due to their lower market value compared to virgin oils
and the fact of being recycled materials from other industrial sectors [70, 71].
The processing of the oil often requires a reduction of the high content FFA via
acid catalysed esterification before the actual raw material can be transesterified to
biodiesel [50].
Kulkarni et al. have recently reported the use of a heterogeneous solid acid cata-
lyst that is able to carry out a simultaneous esterification of the free fatty acids and
transesterification of the triglycerides, giving high FAME yields [72]. Efficient and
low energy intentive protocols of the production of biodiesel from waste oils and
animal fats combining lipases with alkali catalysts have also been reported [73].
Biodiesel from Microbial Oil (Via Transesterification)
Biodiesel from algae oil
. Research is currently ongoing into the production of
biodiesel from microalgae, which are believe to afford greater oil yields than any
known feedstock as has been recently reported [74, 75].
Microalgae are sunlight-driven cell organisms that convert atmospheric CO
2
(via
photosynthesis) into a plethora of chemicals including methane, hydrogen, polysac-
charides and oil [74-76]. The production of microalgal oil is remarkably more
efficient compared to conventional oil crops, providing higher oil yields (up to a
75% dry weight) and lower land area utilisation (Tables 8.1 and 8.2).
The process involves the extraction of the oil from microalgae and subsequent
transesterification with alcohols using homogeneous or heterogeneous catalysts (in
a similar way to that of biodiesel obtained from (non) edible feedstocks) to give
biodiesel.
Significant advances in the field have been recently reported with biodiesel from
microbial oil. Cellana, a joint venture of Shell and HR Biopetroleum recently started
the construction of a pilot facility in the Kona coast of Hawaii Island to grow algae
as biofuel feedstock [77].
Biodiesel from other microbial oils
. Many reports can be found on the subject
using different microbes including various yeast and bacteria [78-80]. A sum-
mary of the main reported microorganisms and their respective oil yields have been
included in Table 8.3.
Table
8.1
Microbial oil content (% dry weight) of various algae species [74
, 75]
Microalgae
Oil content (% dry wt)
Botryococcus braunii
25-75
Chlorella
sp.
28-32
Cylindrotheca
sp.
16-37
Nannochloropsis
31-68
Nitzschia
sp.
45-47
Schizochytrium
sp.
50-77
