The influence of the temperature regime on the formation of methane in a two‐phase anaerobic digestion process

Abstract

The influence of different temperature levels on the formation of methane in a two‐phase anaerobic digestion process using rye silage and barley straw as feedstocks was investigated in this study. This process comprised a leach‐bed reactor (LBR), a reservoir for leachate from the LBR, and a separate downstream fixed‐film anaerobic filter (AF), with immobilized micro biocoenosises. The degree of degradation of the volatile solids was similar in both studies and was almost equal at 75 Ma.‐%VS. When both reactor phases were operated at thermophilic conditions, the main substrate turnover was observed in the LBR (58% of the total methane yield, with an average methane content of 41 Vol.‐%). Only the excess of organic fraction in the process‐liquid was transformed in the AF (42% of the total methane yield, with an average methane content of 74 Vol.‐%). When the parts of the reactor system operated at different temperature regimes, thermophilic hydrolysis/acidogenesis phase and mesophilic methanization, a separation of carbon dioxide and methane production, was observed. A total methane yield of 88%, with an average methane content of 85 Vol.‐%, was formed in the AF. The generated biogas with high methane concentrations is suitable for feeding the purified biomethane into the natural gas grid. Furthermore, it can be used as fuel for cars and tractors.