Utilization of nanoparticles for biogas production focusing on process stability and effluent quality

One of the most important techniques for converting complex organic waste into renewable energy in the form of biogas and effluent is anaerobic digestion. Several issues have been raised related to the effectiveness of the anaerobic digestion process in recent years. Hence nanoparticles (NPs) have been used widely in anaerobic digestion process for converting organic wastes into useful biogas and effluent in an effective way. This review addresses the knowledge gaps and summarizes recent researchers’ findings concentrating on the stability and effluent quality of the cattle manure anaerobic digestion process using single and combinations nanoparticle. In summary, the utilization of NPs have beneficial effects on CH 4 production, process optimization, and effluent quality. Their function, as key nutrient providers, aid in the synthesis of key enzymes and co-enzymes, and thus stimulate anaerobic microorganism activities when present at an optimum concentration (e.g., Fe NPs 100 mg/L; Ni NPs 2 mg/L; Co NPs 1 mg/L). Furthermore, utilizing Fe NPs at concentrations higher than 100 mg/L is more effective at reducing H 2 S production than increasing CH 4 , whereas Ni NPs and Co NPs at concentrations greater than 2 mg/L and 1 mg/L, respectively, reduce CH 4 production. Effluent with Fe and Ni NPs showed stronger fertilizer values more than Co NPs. Fe/Ni/Co NP combinations are more efficient in enhancing CH 4 production than single NPs. Therefore, it is possible to utilize NPs combinations as additives to improve the effectiveness of anaerobic digestion. Article highlights Single NPs (e.g., Fe, Ni, and Co NPs) in low concentrations are more effective in increasing CH 4 production than reducing H 2 S production. Optimal Fe, Ni, and Co NP concentrations enhance anaerobic digestion process performance. Addition of Fe, Ni, and Co NPs above tolerated concentration causes irreversible inhibition in anaerobic digestion. Effluent with Fe, Ni, and Co NPs showed stronger fertilizer values. Nanoparticle combinations are more effective for increasing the CH 4 production than signal NPs.