**2.4 Classification of biomass from an ecological point of view**

a.Primary biomass: Primary biomass includes organic matter formed directly by photosynthetic organisms (algae, green plants, and other autotrophic organisms). This group includes natural and anthropogenic biomass (**Figure 3**). Natural

*Valorization of Biomass as a Raw Material to Obtain Products of Industrial Interest DOI: http://dx.doi.org/10.5772/intechopen.104108*

biomass is that which is produced spontaneously in nature without any human intervention. The resources generated in the natural pruning of a forest are an example of this type of biomass. Anthropogenic biomass includes biomass obtained by human activity such as agricultural residues. Primary biomass is classified into energy crops, agricultural residues, and forestry residues. This group

includes all plant biomass, including energy crops (rape, thistle, eucalyptus), algal biomass (microalgae and macroalgae), agricultural waste (straw or pruning residues), and forestry waste (forestry treatments: obtaining firewood, cleaning to prevent fires and improve access).

