Case study: Valorisation of biowaste in the United States: Distributed biogas upgrading to Renewable Natural Gas (RNG) using biomethanation
Valorisation of biowaste in the United States: Distributed biogas upgrading to Renewable Natural Gas (RNG)using biomethanation
Renewable natural gas deployments in the United States have increased significantly in recent years. As of 3/31/2020, there are 119 operational projects with a further 88 under construction. Renewable natural gas upgrading is a mature technology that processes biogas into high purity methane. Historically, amine, membrane, water scrubbing, or pressure-swing adsorption technologies have been used to perform this gas upgrading through the separation of carbon dioxide and methane. The process of biomethanation instead converts the carbon dioxide into additional methane through the addition of hydrogen.
In addition to increased yields of methane compared to incumbent separations approaches, biomethanation offers potential as a grid-scale energy storage technology by utilizing otherwise curtailed low-carbon electricity to produce the hydrogen needed by the organisms. Being a biological process, the hydrogen and carbon dioxide conversion is quickly ‘rampable’. There have been several pilot- and demonstration-scale installations of the technology and this case study explores some of the economic and environmental considerations.