Dave Elliott: Green gas is being talked up of late as one new way forward for decarbonisation. So what exactly is green gas? It could, in fact, be a lot of different things, some of which are far from green. In general, that depends on the sources and the counterfactuals of using/not using them. Biomass use can be near carbon-neutral, if the replanting rate keeps up with its use, but destroying natural carbon sinks (e.g. by aggressive use of forest products for fuel) means there can be net carbon dioxide rises, while greenhouse gas (GHG) emissions from using fossil gas may be reduced if carbon capture and storage (CCS) is included. In between these extremes there are all sorts of options, including synthetic gas made using surplus renewable power-to-gas electrolysis (P2G). A helpful new report for the European Commission (EC) from The International Council on Clean Transportation offers a three-part classification system. Electricity-generating renewables will obviously rule the roost, as costs continue to fall, and electricity has many good end-uses, but there are also other options that can play a part in meeting energy needs and in balancing variable green electricity power sources. Green gas is one.
Physics World 9th Oct 2019 read more »