Biogas purification and enrichment: sustainability metrics analysis of dry anaerobic digester with cashew apple bagasse substrate

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This study hypothesizes that cashew apple bagasse‐based anaerobic digestion, combined with biochar purification, enhances biogas quality and sustainability. This study aims to investigate the performance and sustainability of a biochar‐based biogas purification technology using cashew apple bagasse as a substrate, with a focus on environmental and energy benefits. The experimental result was the production of 53.7 L of biogas. Thus, the anaerobic digestion of 1 ton of cashew apple bagasse could generate 70 m 3 of biogas with a methane concentration of 63%, which could subsequently be purified to produce 44 m 3 of CH 4 . The purification process effectively increased the methane content from 71% to 78% by the 22nd day, using a 50:50 mixture of activated carbon and zeolites. Sustainability analysis indicated that the cashew apple bagasse‐based biogas purification process achieved a Path2Green score of 0.412, outperforming Study 1 (0.447) and Study 2 (0.232), while matching Studies 3 and 4 (0.447). Regarding the AGREE metric, the process scored 0.50, surpassing Study 2 (0.58) but falling slightly behind Studies 3 and 4 (0.58 each). For the GAPI metric, the process earned a score of 74, higher than Study 2 (85) yet lower than Studies 1, 3, and 4 (85 each). Overall, the results demonstrate the method's alignment with green chemistry principles and its potential for sustainable biogas purification.