Mitigation of Volatile Fatty Acid Build-Up by the Use of Soft Carbon Felt Electrodes: Evaluation of Anaerobic Digestion in Acidic Conditions

Rubén Moreno,Elia Martínez,Olegario Martínez,Rebeca Díez-Antolínez,Xiomar Gómez,Adrián Escapa

doi:10.3390/fermentation4010002

Abstract

Anaerobic digestion and bioelectrochemical systems have great potential to recover energy from waste streams and help overcome common hurdles associated with this process, as integrated technologies. In this study, the benefit of integrating an electrogen-enriched bioanode in a batch anaerobic digester was explored under ambient temperature conditions associated with organic overloading and reactor acidity. An increase in CH4 production was observed in the electrode-containing reactors (0.56 L CH4 kgVS−1 h−1) in comparison with the conventional anaerobic digester (0.14 L CH4 kgVS−1 h−1) during the initial stages of operation. In addition, the mere presence of electrodes operating in open circuit mode resulted in a delay in volatile fatty acid (VFA) build-up. This seems to be associated with the enhancement in VFA consumption due to biomass proliferation on the electrode surface, rather than on electrochemical activity.

Highlights

There have been numerous attempts to utilize geothermal, wind, and solar power as clean and renewable sources of energy for electricity production or cooling processes [1]
Electrogen-enriched electrodes were introduced in a batch anaerobic digester operating under conditions of organic overloading and low temperature
The presence of electrodes improved the initial stages of the operation by delaying volatile fatty acid (VFA) build-up and enhancing the CH4 production rate

Summary

Introduction

There have been numerous attempts to utilize geothermal, wind, and solar power as clean and renewable sources of energy for electricity production or cooling processes [1]. Different technologies are available to turn organic wastes and lignocellulosic biomass into biofuel (i.e., ethanol and biogas) from fermentation processes. The use of wastes allows the recycling of nutrients, in addition to the production of energy, and offers a solution for the disposal of organic materials that are otherwise difficult to reuse (e.g., weeds, animal blood, manure) [3,4]. Anaerobic digestion (AD) has become the main biological process by which to treat organic wastes due to its flexibility and robustness [5]. This process allows the combined treatment of different waste streams taking advantage of their carbon and nitrogen content, making co-digestion a suitable option for increasing biogas yields [6]. Biogas is a renewable energy source that mainly consists of methane and carbon dioxide, and it can be upgraded to about 97% biomethane, which is used as popular renewable forms of energy such as car fuel [7]

Methods

Results

Conclusion