Anaerobic digestion consists on the degradation of organic matter in absence of oxygen and through the action of some specific microorganisms. As a result of this process, the biomass is decomposed resulting in a gaseous product called biogas and a liquid subproduct known as digestate. Biogas is formed mainly by methane (CH4) and carbon dioxide (CO2), therefore it has interest as biofuel. Digestate is formed by inorganic compounds rich in nitrogen, phosphorus and potassium, therefore it can be used as compost for the field or for the production of fertilizers.
Composting is a microbial degradation process of the organic matter in aerobic conditions (in presence of oxygen), which results in a solid product called compost with good properties as an organic fertilizer in agriculture. It consists on a product with a medium degradation grade that stimulate the absortion of water and nutrients from the plants and it reduces the soil erosion. For the compost process all types of easily degradable biomass can be used.