Upgrading of Biogas to Biomethane by using Biochars as CO2 Sorbent in a Pressure Swing Adsorption Device

This work investigates the use of biochar-based materials for the selective simultaneous capture of CO2 and CH4 by Pressure Swing Adsorption (PSA) in simulated feeds of biogas to biomethane. Two biochar batches were produced by pyro-gasification at Equivalence Ratios (ER) of 0.15 and 0.30, in a bench scale rotary kiln fed with vineyard pruning pellets. Samples of these two batches underwent activations treatments with KOH and HCl. Biochar-based materials were tested in a laboratory-scale packed-bed rig, performing PSA of a CO2 (46.50 vol%) / CH4 (53.50 vol%) synthetic mixture, 5-9 bara at ambient temperature. The highest CO2 and CH4 sorption capacities were obtained at all pressures by the material treated with both KOH and HCl, which had by far the highest surface area. The biochar produced with ER=0.30 showed higher the selectivity towards CO2. Results are promising to develop selective sustainable materials for the PSA upgrading of biogas