Highly efficient coproduction of electrical power and synthesis gas from biohythane using solid oxide fuel cell technology

Alleviation of greenhouse gas emissions and air pollutants will require innovative deployment of efficient and clean energy technologies combined with optimal management of waste and renewable resources. This paper describes a novel and highly efficient method of utilising renewable and industrial waste gases using state-of-the-art solid oxide fuel cell (SOFC) technology. Coproduction of energy and useful chemicals using SOFCs is demonstrated experimentally through investigations into the utilisation of biohythane, a gaseous mixture consisting of 60/30/10 vol% CH4/CO2/H2 that is produced from an optimised two-stage anaerobic digestion (AD) process. In this work, the gain in energy yield from two-stage AD is shown to be supplemented with additional gains in SOFC efficiency due to the presence of H2 in biohythane, giving up to 77% increased electrical energy yields from biomass overall compared with utilisation of biogas from single-stage AD in SOFCs. The results therefore show that biohythane production rather than biogas is a highly advantageous route to energy production from biomass. Electrochemical measurements and quadrupole mass spectrometry were combined to gain clear new insights into the fuel conversion mechanisms present. The wide range of products that can be obtained via coproduction has been demonstrated and the techniques reported could be used to dispose and add value to many problematic renewable and industrial waste gas streams.