Green hydrogen production by brewery spent grain valorization through gasification and membrane separation towards fuel-cell grade purity

Abstract

This study focuses on the potential valorization of brewers' spent grain (BSG) through gasification for ultra-pure green hydrogen production via membrane separation. First, a fundamental physicochemical characterization of BSG samples from two different Spanish brewing industries was conducted, revealing high energy content and good reproducibility of elemental composition, thus providing great potential for hydrogen generation in the context of circular economy for the brewery industry. The syngas composition reached by BSG gasification has been predicted and main operating conditions optimized to maximize the hydrogen yield (25–75 vol% air-steam mixture ratio, GR = 0.75, T = 800 °C and P = 5 bar). For gas purification, two Pd-membranes were fabricated by ELP-PP onto tubular PSS supports with high reproducibility (Pd-thickness in the range 8.22–8.75 μm), exhibiting an almost complete H2-selectivity, good fitting to Sieverts’ law and hydrogen permeate fluxes ranging from 175 to 550 mol m−2 h−1 under ideal gas feed composition conditions. The mechanical resistance of membranes was maintained at pressure driving forces up to 10 bar, thus highlighting their potential for commercialization and industrial application. Furthermore, long-term stability tests up to 75 h indicated promising membrane performance for continuous operation, offering valuable insights for stakeholders in the brewery industry to enhance economic growth and environmental sustainability through green hydrogen production from BSG.