Nano-array material enhanced electro-fermentation system for methane production

Published: August 12, 2021

Research project at Zhejiang University, China
Nov. 2020 - Aug. 2021
Supervisor: Prof. Jun Cheng
Keywords: microbial electrofermentation, biomass energy, decarbonization

Introduction

This project aims to design an electro-fermentation methane production device for treating organic wastewater in breweries to solve the following problems:

The existing wastewater recovery device has low organic resource utilization, high cost (about 1 Chinese Yuan/m3), and high energy consumption.
The traditional anaerobic fermentation degradation method has a slow gas production rate, which not only produces harmful gases such as H2S and CO, but also the high concentration of CO2 in the product will inevitably aggravate the greenhouse effect.
The existing electro-fermentation method has high energy consumption and low production efficiency.

Advantages

Design of new reinforced electrodes effectively solves the problems of high cost and low bioattachment of existing electrodes.
Use microbial electrosynthesis system to convert byproduct carbon dioxide into methane, improve the stability and efficiency of methane production in the reactor, and reduce greenhouse gas carbon dioxide emissions.
Energy comes from distributed energy and almost no additional energy consumption is required. Using this device, the methane content can be increased by about 35%, reaching the use standard of Class II biogas product gas, so it can be combined with the current natural gas pipeline and achieve zero carbon dioxide emissions.

Achievements

Design of a high-purity methane production device using electro-fermentation
Simulation and experiment of a new type of turbulent fermentation device
- Blade design and qualitative simulation
- Design of baffles and determination of their inclination angles
- Relationship between device voltage and methane production
Study on the catalytic efficiency of enhanced electrodes
- Comparison of methane production efficiency over different catalysts
- Comparison of reaction current and Faraday efficiency of different catalysts
- Effect of in-situ growth of hierarchical nanoarrays of catalyst materials on electron transfer rate

The innovative anaerobic digestion-microbial electrolysis coupling reaction device can achieve high, stable, and continuous production of high-purity methane. The electric energy provided for the electrolysis of the reaction device comes from wind and solar power, which reduces energy consumption. At the same time, this method relieves the inhibitory effect of by-products on the fermentation reaction during the reaction process and improves the efficiency of the methane-producing system. The CH4 purification chamber further purifies the gas and improves the purity of methane in the produced gas. At the cathode of the reaction chamber, oxygen product is additionally obtained. In addition, an aeration structure is used when gas is introduced into the purification reaction chamber, which can more fully dissolve carbon dioxide and water, improve the efficiency of the reaction, and further increase the yield of methane.
The electrode material of the cathode of the device was optimized. This material can not only promote the attachment of methanogens, but also promote the transfer of extracellular electrons, which significantly increases the reaction rate. It greatly improves the performance of existing nickel-based catalysts, and compared with currently used platinum-based catalysts, it reduces economic investment, has no pollution to the environment, and greatly improves the feasibility of popularization and application.