The concept of fuel was once entirely limited to what kept the home fires and lamps burning. It was the discovery of easily recoverable coal that created the Industrial Revolution and expanded the definition of fuel to include whatever material might keep power plants generating and engines firing. Coal, then oil and natural gas, and now uranium for nuclear reactors, have become continually cheaper in relative terms as time has passed. These fuels provide a concentrated source of heat energy and have enabled the building of industrial facilities, the creation of large cities and the operation of motor cars and trucks at relatively low capital costs.

Reliance on fossil fuels as the principal source of energy has steadily increased during the last century, a dependency that was clearly demonstrated for the first time in 1973, when the Organization of Petroleum Exporting Countries (OPEC) unilaterally raised the price of oil by 300 per cent. Quite suddenly, there was a need to take a serious look at alternative sources of energy that would reduce the dependency on fossil fuels. In addition, the increasing awareness of the effects of global warming - coal, oil and gas being large contributors - and the limited reserves of fossil fuels have accelerated the quest for solutions in energy consumption. Using biomass to produce various fuels certainly represents one of the most promising.

Below: firewood, a traditional biomass fuel.

What are biomass fuels?

An important path to new ways of producing energy is that offered by biomass. The term "biomass" includes wood, other plant materials (i.e. straw, sugarcane bagasse), animal waste, urban organic refuse, etc. So biomass could come either from cultivation of specific energy crops, from the harvesting of natural vegetation (i.e. trees) and from agricultural, plant or animal wastes. This last option is very interesting since it could double in the elimination of waste products which is a major disposal problem in modern society.

Biomass can be used as a fuel in various ways: from traditional fuelwood used for cooking in a very inefficient way (open fires), to very sophisticated modern biofuels such as methane, methanol and ethanol, which are produced with the help of conversion and refining technologies. A further conceivable option is the generation of electricity or heat directly by combustion of biomass with a low water content, especially matter rich in lignin and cellulose, such as wood.

Gas biofuels

Methane:

Via anaerobic digestion, livestock and even human wastes can be treated to produce methane fuel while retaining nitrogen and other vital plant nutrients in the remaining sludge to be recycled as fertilizer. "Biogas" generation is a versatile process that is widely used in developing countries since it depends on a hot climate and is most efficient when manual labour is used for functioning. It ranges in scale from the village-type "Gobar" system of rural India and the Far East that is supplied by only few animals, to a much more intensive and complex system where relatively large volumes of organic matter are continually available. In China, where they have been using this technology for more than 20 years, there are now more than 10 million biogas digesters using animal waste. The prevalent practice of burning firewood and farm waste to meet energy demand is not sustainable since it rapidly results in problems associated with deforestation on the one hand, and loss of soil nutrients on the other.

Any methane produced from livestock waste in the developed world will almost certainly be used on-site, at least in the foreseeable future. However, in the developing world, and especially in India, China and other Far East countries, such organic wastes can go a long way since they can provide much of the energy required by a large percentage of the population.

Liquid biofuels

Bio-ethanol:

This gas can be derived from the fermentation of starch and sugar crops, such as cereals, potatoes and sugar beets, or from relatively novel crops (i.e. Jerusalem artichoke). It is already added as a component of a cleaner-burning gasoline and has the advantage of being a good anti-knock additive in motors. Sugar production represents an interesting combination of energy from biomass and production of fuel. The biomass left after processing sugarcane, called bagasse, is burned for co-generation of electricity and local power. The sugar produced from cane or beets can be fermented into ethanol. In Brazil they are also famous for using part of the sugar product to produce alcohol used for running cars. They have six million cars running with a mixture of 25 percent alcohol in their petrol. This has the advantage of reducing pollution and avoiding the need to use lead, resulting in lead-free petrol. Corn starch is another major source of agri-plant conversion to ethanol in North America.

Biodiesel:

Below: gas pomp.

The production of this type of alternative fuel is done using well established technology but is currently not economically viable without a subsidy. It is usually derived as RME (Rape methyl ester) from oil-seed rape crops. It is less polluting than diesel but can be used in similar ways.

Vegetable oils:

These oils have a long history of use for food and fuel. Burning vegetable oil has been a major source of light over the centuries, but has been displaced in this century petroleum oil, either directly or as fuel used for generating electricity.

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