Anaerobic Mesophilic Codigestion of Rice Straw and Chicken Manure: Effects of Organic Loading Rate on Process Stability and Performance.

Abstract

To investigate the effects of organic loading rate (OLR) on performance and stability of mesophilic co-digestion of rice straw (RS) and chicken manure (CM), benchtop experiments (40L) were carried out at OLRs of 3.0, 3.6, 4.2, 4.8, 6.0, 8.0, and 12.0kgvolatile solid (VS)/(m(3)·day) with volatile solid (VS) ratio of 1:1 (RS/CM) which was based on batch tests. Anaerobic co-digestion was slightly and severely inhibited by the accumulation of ammonia when the digester was overloaded at an OLR of 6 and 12kgVS/(m(3)·day), respectively. The recommended OLR for co-digestion is 4.8kgVS/(m(3)·day), which corresponds to average specific biogas production (SBP) of 380L/kg VS and volumetric biogas production rate (VBPR) of 1.8m(3)/(m(3)·day). An OLR of 6-8kgVS/(m(3)·d) with SBP of 360-440L/kg VS and VBPR of 2.1-3.5m(3)/(m(3)·day) could be considered, if an Anaerobic digestion (AD) system assisted by in situ removal of ammonia was adopted.