Alleviation of ammonia inhibition in dry anaerobic digestion of swine manure

Abstract

The effects of granular activated carbon (GAC) and organic load rate (OLR) on semi-continuous dry anaerobic digestion of swine manure were investigated. A kinetic model of anaerobic digestion provided a good description of the quantitative effect of OLR on the methane production rate, with a maximum methane production rate of 1.46 and 1.60 LCH4/L/d without and with addition of GAC, respectively; this rate reached approximately 80% of the reported maximum methane production rate for the wet anaerobic digestion of swine manure, thus suggesting favorable application prospects of dry anaerobic digestion of swine manure. With an increase in OLR from 1.0 to 5.0 g TS/L/d, the ammonia nitrogen concentration increased from 3433 to 4094 mg/L; after the OLR reached 7.0 g TS/L/d, the ammonia nitrogen concentration decreased, to 3654 mg/L at 7.0 g TS/L/d and 2324 mg/L at 9.0 g TS/L/d, and ammonia inhibition was alleviated. The improvement in the biogas production efficiency with the addition of GAC was apparent at the start-up stage and under high OLR (≥7.0 g TS/L/d).