Experimental Hydrogen Purification from Biogas of Pineapple Residues Using Coconut Husk Biochar: Energy Recovery and Sustainability Assessment

Agro-industrial residues, such as pineapple waste and coconut husk, offer significant potential for dark-fermentative biogas production and waste valorization by anaerobic digestion (AD). This study evaluates pineapple residues and coconut husk biochar for biohydrogen production and purification, respectively, aiming to optimize biohydrogen generation and support sustainable waste-to-energy solutions. Maximum hydrogen fractions of 71.8% (before biochar treatment) and 81.7% (after biochar treatment) were achieved in dark-fermentative (DF) biogas (H2 and CO2) on days 16 and 17, respectively. The coconut husk biochar purification system demonstrated a maximum CO2 removal efficiency of 65.7% as a preliminary concept. Biochar saturation begins on day 19. The functional groups on the biochar in CO2 adsorption indicate their involvement in the adsorption process. Structural changes, such as pore filling, were observed after CO2 adsorption. Electricity generation from 1 ton of pineapple waste was 144.17 moles of H2, which could generate 4.75 kWh of electricity using a 50% efficient fuel cell. Fuel cells offer a clean energy solution and are suitable for a range of applications, including stationary electricity generation and vehicle propulsion. The Path2Green metric achieved a score of 0.523; the AGREE metric scored 0.62; and the GAPI metric scored 85, all indicating strong adherence to green analytical principles and sustainability. The conclusion highlights the potential of pineapple residues and coconut husk biochar for biohydrogen production and purification.