Prof Jerry Murphy presents at the International Energy Agency Low-emissions Gases Day 2025

Prof Murphy’s discussion (from 35 minutes to 1 hour and 5) explores circular economy approaches to biogas, and emphasises:

1. The role of micro-algae in upgrading biogas to biomethane and in doing so potentially providing a major source of economic return in the biorefinery system.
2. Conversion of digestate to biochar with carbon content of c. 80% and specific surface areas approaching 400m2/g. Biochar when applied to land increases soil organic content, crop yields, and photosynthesis, and as such is deemed a negative emission technology. But biochar has many more applications including; enhancing fermentation process, and filtering contaminants from water.
3. Bio-electrochemistry, whereby electrodes inserted in anaerobic digestion can double the methane yield from the feedstock; this is effected by increased degradation of feedstock at the anode, while at the cathode, CO2 is converted to CH4. This is a carbon capture and conversion system, with very high percentages of CH4 in the resultant biogas. We see in the future, electrodes produced via 3 D printing using biochar; these electrodes will be alive with bugs inhabiting the extensive pores of the biochar.
4. An integrated biofuel, biorefinery, e-fuel, e-refinery system whereby biogenic CO2 (by-product of biomethane) can be reacted with hydrogen from electrolysis to produce renewable hydrocarbons such as e-methane, e-methanol (for shipping and green chemistry), e-SAF (sustainable aviation fuel) and e-ammonia (green fertiliser). Hydrogen must be sourced from water, which in many regions is a scarce resource. In our integrated industrial eco-system, we see the role of biochar in upgrading wastewater to water of a standard for use in electrolysis.
5. Biogas is not comparable to a wind turbine; we cannot (or should not) assess its marginal abatement cost from the energy vector it produces, but need to consider the bespoke system into which it fits. Biogas is an essential cog in the circular economy, energy and environmental system.