Experimental study of four-step thermal swing adsorption cycle to upgrade biogas obtained from anaerobic digestion

Biogas is a renewable source of energy that when upgraded can be adopted as a reliable and sustainable alternative. This study evaluates the performance of thermal swing adsorption technology applying resistive heating, in upgrading biogas obtained from anaerobic digestion to biomethane. Commercial coconut shell-based activated carbon was used as an adsorbent in the four-step cycle process to capture carbon dioxide, using a fabricated adsorption model. The influence of minor gas constituents of biogas in carbon dioxide breakthrough curves was analyzed. Dynamic adsorption tests were carried out to evaluate the system performance in carbon dioxide capture. The maximum regeneration temperature of 60 °C was found to have peak carbon dioxide concentration of 39% in the waste gas, maximum energy requirements of 0.1538 kWh per cycle, and an energy efficiency of 87%. This is a good trade-off between adsorbent recovery and system energy efficiency. The adoption of thermal swing adsorption technology in biogas upgrading systems is a viable alternative for water-deficient regions.