Content of the essential and other elements in residues left over after fermentation in a biogas plant

Abstract

The chemical composition of the residues left over after fermentation in a biogas plant depended on the source material that was used. The dry matter content in the liquid residue ranged from 4.83 to 6.82%, pH from 7.80 to 8.20, whereas the content of organic matter in the dry matter of the liquid residue varied from 72.33 to 80.30%. Ash content varied from 19.70 to 27.67%, nitrogen from 2.84 to 3.92%, phosphorus from 0.51 to 0.62%, potassium from 5.07 to 6.86%, calcium from 1.77 to 2.35%, and magnesium from 0.26 to 0.30%. Concentrations of essential micronutrients (Fe, Cu, Mn, Zn and Ni) and Cd and Pb varied within the limits laid out to dry matter of manure. Concentrations of heavy metals were significantly lower than the MAC in the dry matter of fertilizers. Based on the above it can be concluded that the residue left over after fermentation in a biogas plant is, by its chemical properties, suitable organic fertilizer that may be used not only in conventional but also in organic crop production.

Keywords

• biogas plant
• residues left over after fermentation
• chemical characteristics
• essential elements
• heavy metals