Potentiale zur energetischen Nutzung von Biomasse in der ... - EPFL

Anhang 39
Bundesamt für Energie BFE
Anhang 10: Fuel Alcohol: Technology status and perspectives
Introduction
Generalities
In the present context of depleting fossil reserves, crude oil promises to be gradually scarcer and more
expensive in future. Even in the most pessimistic scenarios, nevertheless, the price of oil would never
exceed a certain limit, which would be the cost of substitution by another energy resource such as
coal, nuclear energy, gas, electricity or even bituminous shale. This argument, however, does not
apply to the case of transportation, as for yet many decades, vehicle fuels shall be in liquid form, with
a high energy density. Hence, the dependence of the sector on oil is likely to remain strong, whatever
its price will be, if no alternative is developed.
Ethanol has an authentic history as a vehicle fuel and actually dates back to the debut of the
automobile industry (1876: first combustion engine running on ethanol and gasoline; 1908: Ford's
Model T designed to operate with any mixture of alcohol and gasoline). Since the beginning of the
20 th
century, ethanol has been used on and off, being essentially considered as an alternative to
conventional gasoline in periods of uncertainty. The safeguarding of supplies was most often the
factor determining the use of alcohol. This argument has more recently tended to slip into the
background in favour of the environmental potential that bio-based alcohols provide.
The first major fuel-ethanol programme (Pro-Alcohol) started in Brazil in 1975, followed by similar
programmes in the USA in 1978 and more recently in several European countries. Although many
countries produce ethanol for fuel and other purposes, major production has only occurred in those
countries with especially favourable agricultural and economic conditions.
The blending of small amounts of alcohols or ethers is a method which could be used to quickly
introduce alcohols on a large scale. The use of ethers (typically MTBE and ETBE) involves few or no
changes to conventional gasoline. Several oxygenates (alcohols and ethers) are already available on
the market as components for blending into gasoline. One factor limiting the blending of ethanol into
gasoline has been the hesitation of car manufacturers over providing guarantees for such running.
However, a change is in the way, as modern vehicles have greater fuel flexibility and many
manufacturers are now prepared to provide guarantees for ethanol blends of up to 10%.
The various uses of fuel-ethanol have been widely investigated and its large scale utilization put into
practise successfully in several countries. According to various sources, bioethanol represents one of
the best short-term alternatives to fossil fuels in the transportation sector, in terms of sustainability.
Today, more and more countries around the world are considering the introduction of ethanol in the
vehicle fuels market as a serious option for the very near future.
In practical terms, fuel-ethanol is used in a variety of ways. Today, the major use of ethanol is as an
oxygenated fuel additive. In the US, today, practically all of the ethanol sold is used in a mixture of
10% (vol.) alcohol with gasoline, or so-called “gasohol” (also commonly referred to as E10), which
accounts for approximately 15% of all light-vehicle fuels sold in the country. The European Union has
recommended a 5% admixture of ethanol in all gasoline for internal combustion engines before
2010. As an additive, ethanol must compete with methanol and two petroleum derivatives, namely
methyl and ethyl tertiary-butyl ether (MTBE and ETBE, respectively). The latter is made from ethanol
and both ethers are preferred by the petroleum industry, although MTBE pollution is causing concern
because of its toxic and alleged carcinogenic properties.