Influence of digestate recirculation and recirculation percentage on biogas production from lawn grass via anaerobic digestion

Recirculation of digestate either in the form of liquid or solids has proven to enhance biogas production from energy crops including lawn grass. The explanation to this is that digestate contains suitable bacteria and trace elements (nutrients) needed by methanogens. Influence of digestate recirculation and recirculation percentage in biogas production from lawn grass via anaerobic digestion was studied in laboratory scale digester (1L plastic bottles) at mesophilic condition. Three scenarios were used: digester without recycle digestate (control) (WRD), digestei's with recycled liquid digestate (RLD) and digesters with recycled solid digestate (RSD). Liquid recycled digestate was added in percentages variation ranging from 10%-60%, solid recycle digestate was added in percentages variation ranging from ll)%-50%. The maximum biogas production with methane content of 55% was obtained in the digester with 60% RLD on the 8lh day. During the study of recirculation of solids, highest biogas yield with methane content of 53% was observed in a digester with RSD of 40% on the 5th day. Retention time for both digesters with recycled digestate was reduced and biogas production rate was increased compared to the digester with no recycled digestate.