17 - Valuable energy resources and food-grade CO2 from biogas via membrane separation

Abstract

The circular economy is presented as a cutting-edge perspective to maintain economic development while preserving the environmental quality for future generations. This strategy aims to reduce wastes and residual products as much as possible by their valorization into new valuable products or energy, thus contributing to avoiding depletion of natural resources. This perspective is especially interesting by considering the increasing levels of anthropogenic CO2 emissions during last decades and their direct influence on global warming. The current chapter goes into deep on this concern, analyzing the simultaneous production of valuable energy resources and food-grade CO2. The purity of both compounds is a key factor for the intended applications and selective membranes could provide important advantages against other alternatives. After some general concerns about CO2 emissions, capture processes, and biogas production, two general strategies are distinguished: (1) separation of CH4 and CO2 directly coming from biogas and (2) biogas valorization into green-H2 and further purification. In this context, a general overview of both strategies is pointed out to describe current technological approaches and typically required operating conditions. Moreover, dedicated sections for the most relevant insights reached for a wide variety of CO2 and H2-selective membranes have been addressed.