Biogas production improvement and C/N control by natural clinoptilolite addition into anaerobic co-digestion of Phragmites australis, feces and kitchen waste

Anaerobic co-digestion (A co-D) performance of Phragmites australis, feces and kitchen waste with addition of clinoptilolite (one main kind of zeolite) was investigated to evaluate the improvement of biogas/methane production and internal mechanism of nitrogen and organics control. A better biogas/methane production was observed by 10% clinoptilolite (v/v) than bentonite and diatomite, with the shortest lag phase of 0.070 d(-1), the max rate of 15.89 L/(kg VS day) and ultimate biogas production of 308.2 L/kg VS as the modified Gompertz equation predicted. Accordingly, the content of methane in the biogas was increased from 44.10% to 65.30%. Furthermore, the clinoptilolite inhibited the acidification of digestion liquid (optimum pH 7.0-7.5) and enhanced the VFAs (acetic acid, propionic acid and butyric acid) destruction. Moreover, 10% of clinoptilolite optimally enhanced the microbial utilization of Ca2+/Mg2+, controlled the C/N ratio, and improved the biogas production as well as NH3-N/NO3-N inhibition efficiency. (C) 2014 Elsevier Ltd. All rights reserved.