Perspectives on Bioenergy and Biofuels - Sustainable Biotechnology: Sources of Renewable Energy - page 190

Biodiesel production involving the use of Jatropha curcas (shrub found in
(sub)tropical areas) as a new (alternative) source of fatty acids for its produc-
tion has merited attention in the last couple of years. Jatropha curcas is a
non-food plant (all parts are toxic) that can grow in the wild in arid condi-
tions traditional use has usually been to make soaps and mark land boundaries.
The seeds of the plant can be pressed yielding the oil required for biodiesel
production. Due to growing conditions and non-food properties, it addresses
issues concerning “food-versus-fuel”. While this area is fairly new, entrepreneurs
have already established situations where intercropping of tender agricultural
crops with Jatropha curcas (which protects them from harsh conditions) takes
place. A successful venture in Tanzania has already been established offering
labour to local farmers [33]. Another development is in the production using
algae. The growth of algae is dependant on sun energy and CO 2 and due to
its non-food qualities also helps tackle the “food-versus-fuel” issue. Due to the
depth of penetration and intensity of sunlight required for biomass production,
issues of surface area and location needed have arisen. Interest in the field is
high with Sapphire Energy seeing (new) investments from Bill Gates (Cascades
Investments LLC) [34] as well as Venrock (Rockefeller family venture capital
facility), Arch Venture Partners and Wellcome Trust [35]. As well as this KLM
announced in May 2008 that aims to use biodiesel derived from algae in some of
its aircraft, thus further innovation, development and commercialisations in the
area are reasonably expected.

• Use of (lignocellulosic) rest streams from primary agricultural production, as in

the case of second generation bioethanol and biogas.
It is reasonable to expect that improved biorefinery of agricultural materials will
produce sufficient quality food and will lead to suitable biomass waste streams
that can be used for biofuel production and other fractions that could be used
for value added applications. As discussed elsewhere (Perspectives on chemicals
from renewable resources), biorefinery is taking place for a number of renew-
able raw materials although it will require further development in order to obtain
all (useful) fractions separated from biomass. However with such rest streams
in hand technology is currently well placed in utilising them for bioethanol
production.
The (effective) pretreatment (and hydrolysis) of biomass often uses reagents
such as mineral acids where most effort is involved on improving economics and
reducing waste and focuses on the downstream processing of aqueous streams
to isolate and reuse these reagents. For such materials this is often not trivial.
Alternative strategies either using reagents that don't need to be removed
(because of low cost and innocuous nature) or require less complex procedure
for reuse e.g. direct feeding back into pretreatment should be considered. Where
biotechnological techniques are implemented there are possibilities in obtaining
fermentable sugars from pretreated biomass using cellulases and the conversion
of glucose, xylose (and arabinose) to bioethanol using specially engineered yeasts
and bacteria. Development of cellulases by Novozymes had already led to a
twelvefold reduction in the enzyme cost contribution in bioethanol production to