Enhanced Methane Production using an Integrated Anaerobic Digestion and Bioelectrochemical System

Afrooz Bayat (University of Canterbury), Ricardo Bello-Mendoza (Univestity of Canterbury)

Energy sustainability is becoming an integral part of New Zealand’s society as the country is moving towards carbon-neutral approaches and a net-zero carbon emissions target by the year 2050. In particular, through decarbonisation of
energy and industry emission. As a result, many industries, such as dairy producers, have pledged to change their energy source from fossil fuel to renewables and biomass energy. Biomethane via waste-to-energy is a potential source of renewable energy that can be produced on-site and can replace the coal and petrol used in industry.

Anaerobic digestion (AD) is a well-known technology that have been used worldwide for wastewater treatment as well as biogas production. Anaerobic digestion not only treats wastewater but also generates renewable gas that can be used for heating and electricity generation. Biogas composition can vary depending on the source of wastewater; however, in general, biogas contains 50-60% methane gas, and the rest is mainly carbon dioxide.

The ability to convert waste to valuable energy, as well as treat wastewater, makes anaerobic digestion an interesting process for industries and local government. However, due to the relatively low methane content of the biogas, there is interest for studying ways to improve AD performance in terms of methane output. In this regard, bioelectrochemical systems have been introduced as a potential means of improving biogas composition as well as improving the treatment process. The aim of this research is to study the potential of a bioelectrochemical system integrated to an anaerobic digester to improve methane production efficiency.

Results show that the integrated system does improve the performance of the anaerobic process including higher biogas methane content, COD removal, and solids removal. Methane yield is improved by 17.5% compared to an anaerobic digester alone. COD removal is also improved by 7.3 % while less solids were produced in the integrated system. The results show that integrated AD with bioelectrochemical systems can lower the carbon dioxide content of the biogas and provide a high calorific source of energy obtained from waste.