The energy crops are integrated by a number of vegetal species that are grown to produce energy. The crop raw material obtained is the biomass that can be used as fuel or as a raw material for transport biofuels production. As in the case of the traditional agricultural crops, the energy crops can be herbaceous or woody species.
Presently, some agricultural crops are also being used for energy applications. This is the case of some oleaginous species (soja, rape, sunflower, palm etc.), the cereals, the sugar cane and the sugar beet. Moreover, some forest species traditionally used for wood industry are also of interest to be utilized as fuel. This is the case of willow, poplar and eucalyptus. When these last species are used for energy, specific clones and growth conditions (high planting densities, short rotations) are normally used.
Nevertheless, most of the energy crops under development are different to those traditional forest
The vegetal species or varieties of interest for energy use must be characterised by a high rusticity, much higher, in general, than that shown by the traditional agricultural and forest species or varieties.
Therefore, the energy crops must be resistant to frost and plagues and must have a high efficiency in the use of nutrients and water, which, in practical terms, determines lower requirements of fertilizers, pesticides and water than the traditional crops. In fact most of the energy crops are well adapted to dry growth conditions .