Environmental Engineering Reference
In-Depth Information
lands included the so-called “wastelands”, tropical zones or even arid regions as they
are more likely to proliferate at relatively extreme conditions (e.g. plagues and dry
environments) with a low fertiliser input. Many of the biomass feedstocks are also
self-seeding crops (they do not need to be planted and re-seeded after harvested)
and require little or virtually no fertilizer input. These approaches can therefore be
applied to “marginal lands” where the soil cannot/should not support food crops
[201]. In this way, they will not interfere with the land dedicated to food crops.
They can also provide a solution for the production of quality biofuels in develop-
ing countries (e.g. India) where, for example, a blend of biodiesel obtained from
jatropha and palm has been reported to have a right balance of physical properties
conferring the product with an adequate cold low performance and oxidation stabil-
ity [62], also falling within the acceptable by the American and European biodiesel
standards.
However, the switch to these non-edible feedstocks poses various concerns. The
cultivation patterns of the crops are still under investigation and early studies have
shown relative differences depending on the approach taken to crop cultivation and
oil production management [202]. The crops have only been employed by local
communities for different uses (e.g. soap production and natural crop protection
for the inedible nature of the oil and toxicity of the seeds, respectively) [203, 204].
Therefore, the evaluation of the sustainability index needs of more data to estimate
the real global impact of these crops. Furthermore, the technologies available for
the majority of the second generation biofuels are still in their infancy and need
major developments to be able to sustain a scaled-up production of biofuels for
transport. The economics of the processes may play a key role in the successful
implementation of many of these technologies.
A full discussion on these important topics, with a thorough evaluation of socio-
economic, environmental and related issues, has been recently reported [205]. Some
of the most relevant prospects and challenges for the future of second generation
biofuels will now be detailed.
8.4.1.1 Second Generation Biodiesel
The use of cheap feedstocks (e.g. waste oils and fats) and the potential commer-
cialisation of glycerol (and glycerol derived products) can considerably reduce
the biodiesel production costs, specially taking into account that 70-90% of the
biodiesel cost arises from the cost of the oil [206]. However, the use of high tem-
peratures in the transesterification, incomplete conversion and variability of the
incoming feedstock (with marked differences in water content and FFA depend-
ing on the source, location and usage) are problems related to such feedstocks for
biodiesel production.
The production of methyl esters from algal oil has also recently attracted a
great deal of attention. The enormous diversity of species of algae with high oil
content that require a tiny land utilisation compared to oil crops offers an inter-
esting possibility of industrial exploitation of such organisms in the production of
biodiesel.
