Synergetic effects of anaerobic co-digestion of food waste and algae on biogas production

Anaerobic co-digestion of food waste and algae was assessed to offset the drawbacks of anaerobic mono-digestion of each substrate. Batch test results indicated that a food waste and algae mixture ratio of 8:2 facilitated the highest CH4 yield (334 mL CH4/g CODInput). This ratio was applied to the anaerobic co-digestion reactor, resulting in a CH4 yield that was twice that of the anaerobic mono-digestion reactors, thereby facilitating high operational stability. In contrast to the anaerobic mono-digestion, anaerobic co-digestion resulted in stable CH4 production by overcoming volatile fatty acid accumulation and a decreased pH, even under a high organic loading rate (3 kg COD/m3∙d). Furthermore, a comparative metagenomic analysis revealed that the abundance of volatile fatty acid-oxidizing bacteria and hydrogenotrophic and methylotrophic methanogens was significantly increased in the anaerobic co-digestion reactor. These findings indicate that the anaerobic co-digestion of food waste and algae significantly improves CH4 production and process stability.