Oyster Shell as pH Control Substitute for Two Stage Anaerobic Co-Digestion System

Abstract

Alkali substitute for two-stage anaerobic co-digestion system using kitchen waste, agriculture waste, and horse dung was compared with the standard alkali chemical used for pH control. The substitute used in this experiment is oyster shell waste. The study aims to investigate and evaluate the performance of oyster shells to overcome problems such as pH drops in the hydrolysis stage, greenhouse gas emission from chemical use, and methanogenesis stage performance such as methane gas yield and quality of biogas production. The result shows hydrolysate from control treatment using alkali has the highest volatile solid (VS) (1.18 %) and chemical oxygen demand (COD) (27.7 g/L). Oyster shell treatment has lower VS (1.14 %) and COD (25.01 g/L), but not significantly different from control. One-time oyster shell application can maintain reactor pH throughout the acid phase. Alkali treatment needs multiple doses to maintain the reactor in the intended pH range.