Microbial Diversity in Three-Stage Methane Production Process Using Food Waste

Abstract

Anaerobic digestion is an alternative method to digest food wastes and to produce methane that can be used as a renewable energy source. We investigated bacterial and archaeal community structures in a three-stage methane production process using food wastes with concomitant wastewater treatment. The three-stage methane process is composed of semianaerobic hydrolysis/acidogenic, anaerobic acidogenic, and strictly anaerobic methane production steps in which food wastes are converted methane and carbon dioxide. The microbial diversity was determined by the nucleotide sequences of 16S rRNA gene library and quantitative real-time PCR. The major eubacterial population of the three-stage methane process was belonging to VFA-oxidizing bacteria. The archaeal community consisted mainly of two species of hydrogenotrophic methanogen (Methanoculleus). Family Picrophilaceae (Order Thermoplasmatales) was also observed as a minor population. The predominance of hydrogenotrophic methanogen suggests that the main degradation pathway of this process is different from the classical methane production systems that have the pathway based on acetogenesis. The domination of hydrogenotrophic methanogen (Methanoculleus) may be caused by mesophilic digestion, neutral pH, high concentration of ammonia, short HRT, and interaction with VFA-oxidizing bacteria (Tepidanaerobacter etc.).

Evaluating Feeding of Organic Waste and Stirring Interval to Optimize Anaerobic Digestion

“…Biogas produced by acetogenesis in the anaerobic digestion process with swine manure was 72%, and biogas produced by hydrogenotrophic methanogen was 28% (Lee et al, 2005). However, biogas produced by acetogenesis in the anaerobic digestion process with a mixture of food waste and swine manure was 4%, and biogas produced by hydrogenotrophic methanogen was 96% (Nam et al, 2012). Kafle and Kim et al (2013) reported similar results: they processed a mixture of swine manure and silage that was made with saury and rice bran to supplement protein and fat and obtained 801 mL/g VS of biogas, which was 6% higher than when only swine manure was used (711 mL/g VS).…”

“…Nam et al (2012) investigated microbial community changes of bacteria and archaea in the anaerobic digestion process when using a mixture of food waste and livestock wastewater. They presented a three-step methane production process of livestock wastewater based on acetogenesis, but the process of using food waste was based on hydrogenotrophic methanogen.…”