Mesophilic and Thermophilic Anaerobic Digestion of Organic Fraction Separated during Mechanical Heat Treatment of Municipal Waste

Slawomir Kasinski

doi:10.3390/app10072412

Abstract

The objective of this study was to investigate the effect of process temperature on semi-continuous anaerobic digestion of the organic fraction separated during autoclaving of municipal waste. Tests were carried out in reactors with full mixing. Biogas production was higher in thermophilic conditions than in mesophilic conditions (0.92 L/g volatile solids at 55 °C vs. 0.42 L/g volatile solids at 37 °C, respectively). The resulting methane yields were 0.25-0.32 L CH4/g VS and 0.56–0.70 L CH4/g VS in mesophilic and thermophilic conditions, respectively. In both variants, the methane share was over 70% v/v. This work also discusses the potential impact of Maillard compounds on the efficiency of the fermentation process, which were probably produced during the process of autoclaving of municipal waste. These results indicate that, after autoclaving, the organic fraction of municipal waste can be an effective substrate for anaerobic digestion in thermophilic conditions.

Highlights

Mechanical Heat Treatment (MHT) is a relatively new and poorly investigated technology for processing municipal solid waste
The largest fraction obtained during MHT is the organic remaining fraction (ORF), mechanically separated after full-scale autoclaving of unsorted municipal solid waste (Figure 1)
The objective of this study was to investigate the effect of process temperature on anaerobic digestion of the organic remaining fraction mechanically separated after full-scale autoclaving of unsorted municipal solid waste

Summary

Introduction

Mechanical Heat Treatment (MHT) is a relatively new and poorly investigated technology for processing municipal solid waste. MHT uses a combination of mechanical and thermal-based technologies to separate a waste stream into several component parts and enable further options for recycling and biological treatment. The separated utility fractions produced by MHT, including pre-residual derived fuel (pre-RDF), account for up to 80% of the initial waste mass [1]. The most common method of thermally treating municipal waste is autoclaving. This technology is used by the majority of existing European MHT plants operating on a technical scale [2]. The largest fraction obtained during MHT is the organic remaining fraction (ORF), mechanically separated after full-scale autoclaving of unsorted municipal solid waste (Figure 1)

Objectives

Methods

Results

Conclusion