1 Introduction

The term biomass encompasses a large number of materials of an extremely heterogeneous nature. We can state that everything that has an organic matrix is a biomass. Plastics and fossil materials have been excluded, even though they belong to the family of carbon compounds, because they do not have anything in common with the characterization of the organic materials discussed here. In scientific terms, the word biomass includes every kind of material of biological origin; it is so linked to carbon chemistry which directly or indirectly derives from the chlorophyllian photosynthesis.

The biomass is the most sophisticated storage of solar energy. In fact, through the photosynthesis process vegetables are able to convert the radiant energy into chemical energy and to stock it as complex molecules with high energy content. For this reason, the biomass is considered renewable and unexhaustive, if appro­priately used as a resource; that is, if the use tax of the same does not exceed the regeneration capacity of the vegetable forms.

The biomass is also an energy source that considers as neutral the aim of the greenhouse gas emissions increment. In fact, vegetables, through photosynthesis, contribute to the subtraction of atmospheric carbon oxide and carbon fixation in the textures (a total of 2 x 1011 tons of carbon are fixed in a year, with an energy content of the order of 70 x 103 MTep, which is equivalent to ten times the world’s energy requirements).

The quantity of carbon oxide released during the decomposition of biomasses, if it happens both naturally and through energy conversion processes (even if it is through combustion), is equivalent to that absorbed during the growth of the same biomass.

There is no contribution to the increase of the CO2 level in the atmosphere. There­fore, in this case the improvement in the quotation of the energy produced using bio­masses, rather than fossil fuels, can contribute to the reduction of the CO2 that is emitted into the atmosphere. For this reason, the use of biomass for energy applications is considered one of the priorities of the post-Kyoto development policies [2, 4-6].

Legislative Decree no. 387 of 29 December 2003 defines biomass as ‘the biodegradable part of the products, wastes and coming from agriculture residuals

(comprehending vegetable and animal substances) from the forestry and from the connected industries, as well as the biodegradable part of the urban and industrial wastes.’

There are other terms which are associated with the term biomass, and they are now commonly used in the renewable energy sector, such as ‘bio-fuel’, which generally means ‘every organic substance that is different from petrol, natural gas, carbon or from their derivatives, and which is usable as combustible’, and ‘bio-energy”, which represents the energy produced from biomasses [7].