International Journal of Greenhouse Gas Control 35 (2015) 18–29 Contents lists available at ScienceDirect International Journal of Greenhouse Gas Control j ourna l ho me page: www.elsevier.com/locate/ijggc Process Intensification for greenhouse gas separation from biogas: More efficient process schemes based on membrane-integrated systems Adele Brunetti a,∗ , Yu Sun b , Alessio Caravella c , Enrico Drioli a,c , Giuseppe Barbieri a a Institute on Membrane Technology (ITM-CNR), National Research Council, Via Pietro Bucci, Cubo 17C, Rende, CS 87036, Italy b Department of Materials Engineering, Hanyang University, Ansan-si, Gyeonggi-do 426-791, Republic of Korea c Department of Environmental and Chemical Engineering, The University of Calabria, Via Pietro Bucci, Cubo 44A, Rende, CS 87036, Italy a r t i c l e i n f o Article history: Received 27 October 2014 Received in revised form 22 December 2014 Accepted 6 January 2015 Keywords: Biogas Membranes Gas separation Metrics Process Intensification a b s t r a c t The separation of biogas leads to not only recovery and sequestration of CO 2 , but also to much greater purification and recovery of value-added CH 4 able to be used, for example, to directly feed pipelines for domestic or small plants. In this work, an alternative approach for a preliminary design of separation pro- cess based on the use of polymeric membranes is proposed. Two different types of polymeric membranes were taken into account, Hyflon AD60 and Matrimid 5218, the first showing a higher permeability with respect to other membranes but a quite low selectivity (12.9), the second exhibiting a higher selectivity with respect to other membranes (41 and 100) even though a lower permeability. Four possible opera- tion schemes using two different types of membranes in multistage configuration system are analysed as functions of the main design parameters, i.e., pressure ratio and permeation number. The achieved results are compared with certain targets and are also discussed in terms of process metrics, according to the Process Intensification Strategy. This latter analysis, coupled with a conventional one, provides an alternative point of view over the evaluation of the plant performance taking into account not only the final characteristics of the streams but also process efficiency, exploitation of raw material and energy, and the footprint occupied by the installation. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Biogas represents a versatile raw material, which can be used in a number of applications as an alternative to natural gas from fos- sil fuel source. Biogas is mainly composed of methane and carbon dioxide, besides traces of H 2 S, NH 3 , hydrogen, nitrogen, oxygen and steam (Alves et al., 2013). The concentration of each compound can vary depending on the type of biomass residual used during the anaerobic digestion process among animal waste, sewage treat- ment plants or industrial wastewater, landfills, etc. (Muradov and Smith, 2008). Basically, in a biogas mixture the methane concentration can vary from 55% to 70%, carbon dioxide from 30% to 45%, H 2 S from 500 to 4000 ppm, NH 3 from 100 to 800 ppm, whereas hydrogen, nitrogen, oxygen and steam can show percentage lower than 1 vol.% (Lau et al., 2011; Effendi et al., 2005). ∗ Corresponding author. Tel.: +39 0984 402012; fax: +39 0984 402103. E-mail address: a.brunetti@itm.cnr.it (A. Brunetti). In particular, the biogas can be used in a wide range of applica- tions, as its chemical energy can be transformed into mechanical one through combustion processes (Poschl et al., 2010). It can be useful to co-generate thermal energy by producing hot water and steam through engines operated at a high temperature or can be burned to generate heat in boilers. It is also important as a direct fuel for automotive applications or in reforming processes to gener- ate hydrogen to be further supplied to fuel cells (Herle et al., 2004; Papadias et al., 2012; Iulianelli et al., 2015). However, the pres- ence of incombustible and acid gases like CO 2 and H 2 S strongly lower the fuel calorific value and, moreover, their corrosive nature of these gases reduces the possibility to compress and transport over long distances. In addition, the presence of fouling traces including, for examples, siloxanes can induce fouling in engines and turbines. The biogas upgrading is currently one of the most studied options in biogas treatment leading to the production of bio- methane that can be directly supplied to natural gas grids. Activated carbon is the most used material for siloxanes removal, whereas H 2 S can be usually removed by dry oxidation or absorption. http://dx.doi.org/10.1016/j.ijggc.2015.01.021 1750-5836/© 2015 Elsevier Ltd. All rights reserved.