Membrane applications for biogas production and purification processes: an overview on a smart alternative for process intensification

Abstract

Biogas is the result of a complex conversion process that takes place because of the metabolic activity of various types of bacteria. The anaerobic digestion (AD) plants are characterized by many different criticisms, which risk their failure. One of these is the washout phenomena that imply a premature removal of the active biomass, owing to a vigorous addition of organic matter. There is also the possibility of generating an excess of digestate with high nitrogen and phosphorous content that can induce water eutrophication if left freely in nature. In this sense, membranes can be useful; with their high separation power, they can be employed for both the stabilization of the exhausted digestate and the enhancement of the solid retention time (SRT). Membranes are promising, even in the field of final biogas separation for bio-methane production. To date, various types of setups have been tested for capturing CO₂, and the results indicate a possible stable application for anaerobic digestion plants. Therefore, membranes are a good choice for the development of advanced processes optimized for both gas and semi-liquid phase handling.