Effect of organic loading rate on anaerobic digestion of pig manure: Methane production, mass flow, reactor scale and heating scenarios

Abstract

The effect of organic loading rate (OLR) with total solid (TS) control (3%-8%) on the performance of anaerobic digestion of pig manure (PM) using completely stirred anaerobic reactor was investigated. Based on the lab data, how OLR affects mass flow, construction scale and heating requirement in a farm-scale biogas plant was calculated. And three scenarios of typical reactor-heating technology were comparatively analyzed. The optimal OLR was 1.89 g volatile solid (VS)/(L^.d) with methane yield of 438.38 mL/gVS in the lab condition. The lower OLR, the larger amount of water and energy consumption, lower methane production and larger amount of liquid digestate was observed. Thus, the reactor with low OLR was suitable in tropical regions with the main target of disposing PM and fertilizer production. High OLR has advantage in the investment, but owns risk of instable process for a long-term run. In our study, among the three heating supply scenarios, biogas boiler was the best option for the designed biogas plant with the given breeding scale under moderate OLR. Combined heat and power (CHP) has potential advantage for the biogas plant under high OLR.

Keywords: Anaerobic digestion; Biogas plant; Mass flow; Organic loading rate; Pig manure.