The degassed biomass contains all the nutrients that enter the biogas plant with the feedstock. The nutrients are made more accessible to plants during the anaerobic digestion, and the degassed biomass, therefore, has a greater fertilizer value than the incoming feedstocks.
The mechanical separation is especially applicable, when distribution of the degassed biomass to local farmland is not possible. Solid biofertilizer, which is the solid fraction from the mechanical separation, is a storage stable product with a high fertilizer concentration. Therefore, the solid biofertilizer can be transported over long distances.
Mechanical separation of the degassed biomass can be a decanter centrifuge or a screw press. The degassed biomass is separated into two fractions: a fiber fraction (solid biofertilizer) containing most of the dry matter, and a thin liquid fraction (reject water) primarily containing water soluble nutrients. The reject water can be treated further in Renew Energy’s concept for advanced nutrient recovery.