Biodiesel was probably the first of the alternative fuels to really become known to the public. The great advantage of biodiesel is that it can be used in existing vehicles with little or no adaptation necessary. Biodiesel is, naturally, a compromise for this reason, but still balances positively on the energy scales. There are energy plants available that will produce a higher yield in kWh per area, but the simplicity of having a fuel that is fully compatible with present fuel and engine technology makes it very attractive.
Cars running on BioEthanol, which is produced from agricultural crops, sugar cane or bio-mass, are governed by the same law of physics as those using gasoline. That means both emit CO2, as an inevitable consequence of the combustion process. But there is a crucial difference: burning ethanol, in effect, recycles the CO2 because it has already been removed from the atmosphere by photosynthesis during the natural growth process. In contrast, the use of gasoline or diesel injects into the atmosphere additional new quantities of CO2 which have lain fixed underground in oil deposits for millions of years.
Biogas is becoming increasingly interesting as an alternative to natural gas. It is especially useful that the composition is practically identical, so the same burners can be used for both fuels. Biogas can be produced from plant or animal waste, or a combination of both. There are many different methods used dependent on the starting material and quantity involved. A mixtrue of both has proven to be the best method. The animal waste produces the nitrogen needed for growth of the bacteria and the vegetable waste supplies most ofthe carbon and hydrogen necessary.
Biomass can be a practicable alternative for small district heating schemes in rural areas. Traditional biomass is wood residue and excess straw from agriculture being burned to provide heat or power. There are also gasification plants that produce a gas composed mainly of carbon monoxide and hydrogen from plant material. This has the advantage of being capable of transportation by pipeline or being filled into cylinders for distribution. Pyrolyis, as it is known, is being investigated in many countries presently.
Pyrolysis of Biomass
Pyrolysis of Biomass is used to produce a mixture of three combustible products from biomass: tar, gas and coke are formed in varying proportions. After cleaning the gas can be used to drive turbines or gas motors. The tar is also suitable for the plastics industry and the coke can also be burned in the conventional way.
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