Performance Monitoring of Anaerobic Digestion at Various Organic Loading Rates of Commercial Malaysian Food Waste

Afifi Zainal; Razif Harun; Syazwani Idrus

doi:10.3389/fbioe.2022.775676

Performance Monitoring of Anaerobic Digestion at Various Organic Loading Rates of Commercial Malaysian Food Waste

Front Bioeng Biotechnol. 2022 Mar 24:10:775676. doi: 10.3389/fbioe.2022.775676. eCollection 2022.

Authors

Afifi Zainal^{1

2}, Razif Harun², Syazwani Idrus³

Affiliations

¹ Department of Generation and Environment, Renewable Energy and Green Technology Unit, TNB Research Sdn. Bhd., Kajang, Malaysia.
² Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Malaysia.
³ Department of Civil Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang, Malaysia.

Abstract

Application of anaerobic digestion (AD) has become common in treating palm oil mill effluent in Malaysia; however, employing AD in treating the organic fraction of municipal solid waste (OFMSW), especially food waste, is still scarce. This study aims to characterize the commercial Malaysian food waste (CMFW) and determine its potential as sustainable bioenergy feedstock through biogas production. The sample was digested via the biomethane potential (BMP) test with the variation of organic loading rates (OLRs), ranging from 0.38 to 3.83 gCOD/L. day, under mesophilic conditions. The digestion process was further evaluated in continuous operation using a 6-L continuous stirred-tank reactor (CSTR). The kinetic properties of the process were also determined. It was found that the CMFW had a significant amount of chemical oxygen demand of 230 g/L and an acidic pH of 4.5 with the carbon to nitrogen (C/N) ratio at 121:1. A maximum methane composition of 81% was obtained at 1.92 gCOD/L in the BMP test with specific methane production (SMP) at 0.952 L. CH₄/L.COD fed. The biogas production was well-fitted with the modified Gompertz model with R ² at 0.9983 and the maximum biogas potential production rate at R_m 0.1573 L/day, whereas in the CSTR operation, a maximum methane composition of 85% was produced at OLR 6 gCOD/L. day with the SMP of 1.13 L. CH₄/L.COD fed. The CSTR system was in high stability as the pH was maintained in a range of 6.6-6.7, with an alkalinity ratio of 0.28. This study indicates the CMFW is a sustainable feedstock for biogas production in Malaysia. Toward a circular economy approach, the authorities shall introduce commercial scale CMFW AD as part of managing municipal solid waste issues in Malaysia.

Keywords: anaerobic digestion (AD); biomethane potential (BMP) test; continuous stirred-tank reactor (CSTR); organic fraction of municipal solid waste (OFMSW); organic loading rate (OLR).