Recent advances in anaerobic digestion of lipid-rich waste: Challenges and potential of seaweeds to mitigate the inhibitory effect

Abstract

• Lipid-rich waste (LRWs) represents a potential feedstock for biogas production. • Microbial structure and activity play a significant role in LRWs digestion and biogas yield. • Foaming, fatty acids accumulation, and nutrients imbalance are the main challenges. • Seaweeds provide a complementary co-substrate and a synergistic action to mitigate the effect. • Co-digestion of LRWs and seaweeds enhance the economic feasibility up to 18.9-times. Considerable attention has been devoted towards anaerobic digestion of lipid-rich waste (LRWs) due to their higher energy content comparing to other waste rich in carbohydrates and proteins. However, there are still many challenges for LRWs anaerobic digestion which are mainly attributed to floatation, foaming, long-chain fatty acids (LCFAs) accumulation, and nutrients imbalance resulting in reactor instability and failure. The present review aims to report the recent progress in LRWs production, with a special focus on the main challenges for anaerobic digestion and the recent advances to enhance the digestion process including pretreatment, microbial acclimatization, dosing of trace elements, carrier addition, and co-digestion. Regarding the later, main characteristics and potential of seaweeds to mitigate the toxic effect of LRWs towards enhanced anaerobic digestion through cascading approach was discussed. Considering the low nitrogen content in LRWs and moderate nitrogen content in seaweeds with very low lipid content and negligible lignin, seaweeds could be a potential co-substrate for anaerobic digestion with LRWs. Co-digestion of seaweeds with LRWs results in synergistic action leading to nutrient balance and enhanced anaerobic performance. In addition, developing a cascading approach for high bioenergy recovery from LRWs through co-digestion with seaweeds/residues could further provide optimum conditions for enhanced biogas production and economic feasibility. The economic analysis estimated US$ 15.27 million annual net profit from co-digestion of LRWs and seaweeds, which was 1.0- and 18.9-times higher than that from mono-digestion of LRWs or seaweeds, respectively. The present article suggests a new perspective for efficient anaerobic digestion of LRWs towards enhanced energy recovery through integrated cascading approaches.