Biomethane upgrading to transportation fuel quality using spent coffee for carbon dioxide capture in pressure swing adsorption

Biomethane upgrading from raw biogas is a potential fuel for transportation to minimize the greenhouse gases emissions from the transport sector. Biomethane upgrading a binary biogas comprising 32% CO2 and 68% CH4 by pressure swing adsorption of two beds-four steps process, mediated by spent coffee was experimentally studied. Breakthrough curves experiment was conducted to investigate the methane/carbon dioxide adsorption over spent coffee adsorbent at pressure of 2 bar. From the experimental results, a model was developed using Aspen Adsorption platform to estimate the temperature profile of the spent coffee's bed at four positions of 1 cm, 5 cm, 7.5 cm, and 10 cm. In addition, the upgrading process performance in the presence of three different moisture contents of 3%, 5%, and 10% was also investigated. The experimental data showed that the developed model could represent the process performance with high degree of accuracy. Results from this study reveal that spent coffee with PSA system operated under specific operating conditions yielded biomethane with purity of 97% and recovery of 95.43%. Introduction of moisture with concentration up to 10% improved the CO2 removal rate and accordingly the biomethane purity. This study presents raw coffee as an effective adsorbent, competing other classes of carbon-based materials in separating CO2 to produce high biomethane purity that matches the transportation fuel quality.