Comparison of Two Process Schemes Combining Hydrothermal Treatment and Acidogenic Fermentation of Source-Separated Organics.

Long Lin,Bipro R Dhar,Elsayed Elbeshbishy,Hisham Hafez,Ehssan Hosseini Koupaie,Armineh Azizi,Amir Abbas Bazyar Lakeh

doi:10.3390/molecules24081466

Abstract

This study compares the effects of pre- and post-hydrothermal treatment of source- separated organics (SSO) on solubilization of particulate organics and acidogenic fermentation for volatile fatty acids (VFAs) production. The overall COD solubilization and solids removal efficiencies from both schemes were comparable. However, the pre-hydrolysis of SSO followed by acidogenic fermentation resulted in a relatively higher VFA yield of 433 mg/g VSS, which was 18% higher than that of a process scheme with a post-hydrolysis of dewatered solids from the fermentation process. Regarding the composition of VFA, the dominance of acetate and butyrate was comparable in both process schemes, while propionate concentration considerably increased in the process with pre-hydrolysis of SSO. The microbial community results showed that the relative abundance of Firmicutes increased substantially in the fermentation of pretreated SSO, indicating that there might be different metabolic pathways for production of VFAs in fermentation process operated with pre-treated SSO. The possible reason might be that the abundance of soluble organic matters due to pre-hydrolysis might stimulate the growth of more kinetically efficient fermentative bacteria as indicated by the increase in Firmicutes percentage.

Highlights

In the world, about 1.2 billion tonnes of food are wasted every year through the food supply chain, accounting for one-third of the food production [1]
In system-1, raw source separated organics (SSO) was fermented followed by post-hydrolysis of dewatered solids from the fermentation process
Previous studies have reported the fermentation of model hemicelluloses by Prevotella strains and Butyrivibrio fibrisolvens [23]. Those unidentified genera sorted to the family Ruminococcaceae and the order Clostridiales (Firmicutes) were substantially higher in relative abundance in system-2, which contain a variety of fermentative bacteria [2,25]. These results indicated that there might be different metabolic pathways for volatile fatty acids (VFAs) production in the fermentation process with pretreated SSO

Summary

Introduction

About 1.2 billion tonnes of food are wasted every year through the food supply chain, accounting for one-third of the food production [1]. In Canada, more than 27 million tonnes of food waste are disposed of annually [2]. The large amount of organic waste may cause significant social, environmental, and economic challenges. Source separated collection has been an effective management strategy to separate organic waste from other waste streams at the source, thereby minimizing the contamination of organic waste for the downstream process. SSO contains other organic components, including yard trimmings (grass, leaves, etc.), fibres (paper towels, napkins, tea bags, etc.) and wood waste [4]

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Conclusion