Co-digestion of Ensiled Napier Grass and Commercial Bakery Wastewater for Bioenergy Production

Abstract

Bioenergy derived from anaerobic digestion has gained attention for a decade because of its ability to convert waste into biogas. The advantages of this biotechnology could substitute conventional energy, lower greenhouse gas emissions, and produce less biodegradable waste. This study focused on methane production from ensiled Napier grass (Pak Chong 1) by co-digestion with anaerobic mixed cultures of an Expanded Granular Sludge Bed (EGSB) from a bakery factory. The ratio of co-digestion between ensiled Napier grass feedstock and inoculum (F/I ratio) was 1:1 and 1:3 based on volatile solids (VS). The potential of methane production was evaluated using a batch experiment for 30 days in the laboratory at room temperature (32-35 ± 5 ºC). To enhance biogas production, an alkaline pre-treatment of Napier grass was prepared by adding 1% NaOH. The results demonstrated that the methane production potential of the F/I ratio at 1:1 and 1:3 was 311.11 ± 29 and 255.56 ± 91 mL CH₄/g COD, respectively. The maximum energy production based on methane production was approximately 9.17 kJ/L. The range of pH was 6.96 ± 0.2 to 9.93 ± 0.2 and the percentage of SS, TS, and COD removal were 60.10, 24.69, and 48.63, respectively. The results of this study indicated that the feedstock and inoculum ratio (F/I) including pretreatment of feedstock and inoculum is necessary for biogas potential production. The potential biogas production of the CSTR reactor and its economic feasibility should be further considered.