From biogas to biomethane: A process simulation-based techno-economic comparison of different upgrading technologies in the Italian context

Abstract

Biogas production and its upgrading to obtain biomethane for use as a transportation fuel has been receiving increasing attention, particularly in Italy. In this work, three commercially developed technologies (Pressure Water Scrubbing, Hot Potassium Carbonate and Pressure Swing Adsorption) are critically compared. Accurate process simulations were carried out to evaluate and optimize the performances in terms of biomethane (and CO2) purity and recovery, as well as specific energy consumption and operating costs, considering a biogas throughput of 500 Nm3 h−1. Results from process simulation were used to develop a detailed Discounted Cash Flow analysis of the different technologies, taking into account the recent subsidies issued on March 19th, 2018 by the Italian legislation to promote biomethane development. All the three processes here considered are able to recover more than 90% of biomethane, with a purity higher than 98%. The economic analysis revealed that, according to the new incentive mechanism set by the Italian so-called Biomethane Government Decree (Government Decree 19/3/2018) the investment payback time would range between 3 and 6 years and the Net Present Value would be positive, whereas in the absence of any incentive the investment would not be profitable for any of these technologies.