Liquid biofuels
Practical Action
destroying life. These sugar factories were very dirty operations - many still are. Developing a
market for ethanol can form part of a beneficial re-use strategy that can clean sugar factories
and use the residues that previously had no value and were dumped. With advanced
technologies now available, biomass, such as trees and grasses, can also be used as
feedstocks for ethanol production.
A vast variety of oil plants originate in the tropics and subtropics. Many oil-bearing plants,
whose oils are often toxic to humans, grow on low-grade land, or in marginal locations
unsuitable for food crops. Some of these plants are cultivated on waste lands to prevent
further erosion and to inhibit desertification. Use of these oils for energy provision does not
need to compete with food production. Examples of these oil plants are the Physic nut tree
(Jatropha Curcas L.), the castor oil plant varieties (Ricinus communis L.) and the babassú
palm (Orbignya phalerata Mart.), among others.
Some oil plants grow in symbiosis with food plants by being used, for example, as shade trees,
or to provide barriers against animals; jatropha is not eaten by animals so can be used in this
way. Plant oils from seeds such as jatropha (which grow in many regions of tropical and
subtropical countries), can be harvested and the oil extracted using hand tools. This local oil
production strengthens decentralized supply, provides employment and income opportunities
for the local population and promotes sustainability. The presscake, a by-product of the oil
processing, can be used either as fodder or as high-quality fertilizer. In general, all plant oils
which are liquid at ambient temperatures can be utilized as cooking fuel (Stumpf, 2002).
Large-scale cultivation of biofuels
The problems associated with growing biofuels stem from the industrialised world trying to
grow its way out of its dependence on the internal combustion engine, and the huge profits
that are to be made from growing palm oil and other high energy crops. A single hectare of oil
palm may yield five tonnes of crude oil (Mongabay.com) – and where rainforests are cleared,
for example in Malaysia, further profits can be made through the sale of timber from land
clearance. There is evidence that not all cleared land is suitable for palms and that hardwood
is the main objective. This indiscriminate culling of forests has led, for instance, to oil-palm
plantations covering 5.3 million hectares of Indonesia (2004).The destruction of prime forest
has led to major social and cultural upheaval for indigenous peoples whose rights have been
ignored (Mongabay.com).
After 25 years, lands are often so leached of nutrients that they are abandoned and become
scrubland where few plants will grow. In the USA, which is seeking to reduce its dependence
on overseas oil products, subsidies may mask the costs of spraying both pesticides and
fertilizers, and from using of large-scale farm machinery.
How are biofuels made?
Bio-ethanol
Raw material (eg
sugar cane residue)
Grinding or chipping to
reduce size
Breakdown by enzyme
of cellulose into
glucose
Hydrolysis* into simple
sugars & cellulose
Enzyme production through
chemical reaction to break
down cellulose
Glucose
fermentation**
Simple sugar
fermentation**
Ethanol
Carbon dioxide
Woody waste
used to power
process
* Chemical reaction caused by addition of dilute sulphuric acid on the active ingredients in the feedstock
** Series of chemical reactions that convert sugars through action by yeast or bacteria to ethanol and carbon dioxide
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