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Sustainable development: the hydroelectric energy.
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Generally speaking, with the term biomass we can consider the whole material of organic origin, both vegetable and animal. Intuitively this definition refers to a great deal of very heterogeneous material. It’s possible to distinguish real raw materials (arboreal and herbaceous crops) and products of discard derived by manifold activities that interest the agricultural-forest compartment (residual of agricultural-forest, zoo technical activities), the industrial compartment (discards in wood industry, discards in agriculture and food industry and paper industry) and finally the sector of the urban solid waste. The solid, liquid or gaseous fuels derived from these materials (directly or following a process of transformation) are defined bio-combustible, while any energy obtained from a process of conversion of bio-fuels is defined bio-energy. The energetic conversion mainly happens through thermo-chemical and biochemical operations. The thermo-chemical processes are:
Combustion: it is simpler than the thermo-chemical process and consists in the total oxidation of the fuel to H2O and CO2;
Gasification: the gasification process consists in the transformation of a solid or liquid fuel, in the case of biomass, into gaseous fuel, through a thermal decomposition (partial oxidation) at high temperature. The gas produced is a mixture of H2, CO, CH4, CO2, H2O (steam) and N2, with addition of ashes in suspension and hydrocarbon traces. The proportion among the various gaseous components considerably changes depending on various types of gasifiers, of fuels and their damp content.
Pyrolysis: it is a process of thermal degradation of a material (in the specific of the biomass) in absence of agents oxidizing (air or oxygen) who takes to the production of components solid, liquid and gaseous.
At present co-combustion and co-gasification processes are being developed in order to use, in the same system, biomasses and traditional fuels such as the coal.
The biochemical processes essentially regard the anaerobic digestion, that is the degradation of the organic substance in oxygen absence due to a few bacterial stumps. This process concerns the biomass with a high degree of humidity (zoo technical reflows, the organic part of the solid urban waste) leading to the biogas production (CO4 and CO2) and it can happen both in rubbish tips and reactors suitably planned called digesters.