Abstract

Food waste (FW) utilized as substrate for anaerobic digestion (AD) to produce biogas is promising. Simultaneously, waste is handled and value-added products such as biogas and fertilizer are produced. Palm oil mill effluent (POME) is used as the co-substrate. This study aims to simulate the complete process flow of anaerobic co-digestion (AcoD), consisting of pre-treatment of feedstock, biogas upgrading, wastewater treatment and sludge dying using SuperPro Designer. Parameters, namely hydraulic retention time (HRT), recycle ratio of sludge, water to FW ratio (kg/kg) and co-substrate to FW ratio (kg/kg), would affect the performance of digester. The optimization of these parameters is performed using Design-Expert software, involving response surface methodology (RSM). The effects on responses such as methane flow, chemical oxygen demand (COD) and volatile solid (VS) removal efficiencies are analyzed. In treating 25,000 kg/h of feed, the optimized values for HRT, recycle ratio, water to feedstock ratio, POME to FW ratio are 37.2 days, 0.381, 0.027 and 0.004, respectively. The methane yield is 0.30 L CH4/g of COD removed, with COD and VS removal efficiencies of 81.5% and 68.9%, respectively. The project is profitable, with a payback period of 6.14 years and net present value (NPV) of $5,680,000. A comprehensive understanding of AD matures it for commercialization purposes.

Highlights

  • The disposal of Food waste (FW) poses an environmental issue due to the emission of methane gas and must be handled properly. As it is a suitable feedstock for anaerobic digestion (AD), waste can be transformed into energy via a sustainable method

  • response surface methodology (RSM) was used to investigate the effects of independent variables such as hydraulic retention time (HRT) (A), recycle ratio of anaerobic sludge (B), water:feedstock ratio (C) and Palm oil mill effluent (POME):FW ratio (D) on response variable such as methane flow, chemical oxygen demand (COD) removal efficiency

  • The model’s fit and accuracy is evaluated using the coefficient of variation (CV) and coefficient of determination, R2

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Summary

Introduction

The disposal of FW poses an environmental issue due to the emission of methane gas and must be handled properly As it is a suitable feedstock for AD, waste can be transformed into energy via a sustainable method. AcoD of FW is a promising technology that offers substantial benefits in aspects such as social, economy and environmental This method helps in moving up the waste hierarchy and reduce methane emission. The parameters affecting the methane produced, COD and VS removal efficiencies will be analyzed using Design-Expert software. This provides a comprehensive understanding on how to optimize and maximize the biogas production. Improvements were listed to increase the reliability of the simulation

Characteristic of Feedstock
SuperPro Designer Simulation
Pre-Treatment of Feedstock
AD Process
Biogas Upgrading
Wastewater Stabilization and Sludge Drying
Statistical Analysis Using Design-Expert Software
Methane Flow
COD Removal Efficiency
VS Removal Efficiency
Optimization Using RSM
Economic Analysis
Limitations and Improvements
Conclusions
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