The biomasses are made from material of biological origin which can be used as an energy source. With the term biomass are considered generically all organic substances, solid, liquid and gaseous, which can be used as energy sources directly or through changes in other substances.

The current legislation provides several definitions of "biomass".
The Legislative Decree n ° 3 2011 28 March, recepente the European Directive 2009 / 28 / EC on the promotion of renewable energy sources, in Article 2 defines biomass as "the biodegradable fraction of products, waste and residues from biological origin agriculture (including vegetal and animal substances), forestry and related industries including fisheries and aquaculture, the cuttings and prunings from the public and private green, as well as the biodegradable fraction of industrial and municipal waste. "

As the biomass organic material originating from non-fossil biological cycles (plants and animals), is available and renewable within the limits of reproducibility of the cycle of origin. Ultimately, the energy provided by biomass energy from the sun, which is converted through processes of photosynthesis.

Although the biomass to be an important source of energy, both for the direct know, both for the production of biofuels and biogas, it is necessary that their exploitation is sustainable throughout the supply chain.
From this point of view CHP is an important tool to make the most of this precious resource.