Membrane biogas upgrading processes for the production of natural gas substitute

The biogas processing and production of natural gas substitute have gained importance in recent years. It is often considered to be superior to the production of electricity with internal combustion engines mainly because of the better energy utilisation. The processed biogas in the form of natural gas substitute can be supplied to the already developed natural gas grids and delivered to households and industry. Alternatively, it can be used as a fuel for CNG-vehicles.The present work reviews the literature information that is available on the biogas upgrading processes, the biogas compositions and the permeation of biogas components through typical polymeric membranes. Subsequently, the membrane configurations for biogas upgrading are discussed and thoroughly simulated using numerical modelling. The work proposes basic concepts for the integration of membrane biogas upgrading plants into biogas plants while taking into account the permeate utilisation and the heating requirements of biogas plants.The membrane gas permeation systems provide enough flexibility for heat integration within biogas plants. The expected energy requirement for a single produced cubic meter of natural gas substitute is equal to around 0.3 kWh.