Environmental Engineering Reference
In-Depth Information
ascertain the impact of ethanol-blended fuels. Researchers report benzene emissions
reduction up to 50% with the ethanol-blended fuels. Emissions of 1,3-butadienes
were also substantially decreased in the range from 24 to 82% [196].
8.3.3 Effect of Ethers as Biofuels in Spark Ignition Engine
Performance Properties
The industrial production of tert-alkyl ethers has a rising interest for refineries,
due to reformulated gasoline obtained with respect to EURO standards applied in
Europe, Australia and New Zealand [197]. The asymmetric ethers are synthesized
through an addition reaction between the alcohols and the tertiary olefins of high
reactivity which may be found in the hydrocarbons flow coming out of destruc-
tive processes such as catalytic cracking and pyrolysis [197]. In this way, ethers
including ETBE (C
4
H
9
-O-C
2
H
5
), and TAEE (C
5
H
11
-O-C
2
H
5
) can be prepared
as alternative fuels. In France, Spain and Germany, ETBE is usually mixed with
gasoline in proportions up to 15 vol% [198]. It is produced by the etherification
of isobutene, usually present in a mixture of C4 isomers, with ethanol [188, 190,
197, 198]. ETBE is an adequate substitute for methyl tert-butyl ether (MTBE), an
oxygenating additive that is currently prohibited in many countries due to its tox-
icity and contamination of underground waters [199]. These ethers offer several
advantages with respect to ethanol in terms of low latent heat of vaporization, low
solubility in water and higher combustion enthalpy [200].
8.4 Future Prospects and Challenges
8.4.1 Future Prospects: 1st Vs 2nd Generation Biofuels
Various interesting conclusions can be drawn from the use of first and second gen-
eration biofuels. 1st generation biodiesel and bioalcohols have many advantages as
petrol-fuel replacements but also important disadvantages. The main concern related
to the production of first generation biofuels comes from the fact that the conven-
tional biofuel production process generally involves the use of 'food' crops. This
issue has generated much controversy in a world where the limited area of arable
land and grain reserves may contribute to skyrocket the food prices if we carry on
using such food crops extensively for biofuel production. That and other issues that
arise related to deforestation, global warming and biodiversity threatening, in partic-
ular in developing countries (e.g. Malaysia as a consequence of the use of vegetable
oils (e.g. palm oil) for the production of biodiesel) encouraged the search for alter-
native technologies and feedstocks for biofuels production and the development of
second generation biofuels.
The production of biofuels from second generation biofuels from non-edible
feedstocks has interesting features. Non food crops can be cultivated in alternative
