with V is digester volume (m3
), a is safety factor, and is retention time (days).
The amount of fertilizer resulted is calculated by assume the solid fertilizer as the solid residue that not be
degraded by microorganisms. The solid residue is the deduction of total solid in raw material with the amount of
organic compound in raw material that be degraded by microorganisms to produce biogas in anaerobic digestion
process. The nutrition that is used for microorganisms growth will be leaved in the sludge residue and together with
organic compounds that not be degraded can be utilized as fertilizer. The organic compound degraded is the
multiplication of organic content in raw material with conversion factor. The fertilizer resulted, mp (kg/day), is
calculated by