A meta-analysis of iron-based additives on enhancements of biogas yields during anaerobic digestion of organic wastes

Abstract

The profitability of biogas industries largely depends on substrate biodegradability. Most of the substrates for sustainable energy recovery via anaerobic digestion like lignocellulosic materials contains complex polymeric substances and requires some enhancements to achieve optimum biodegradability. Previous studies have reported that the use of iron additives improved both degradability of such substrates and biogas yield, but iron-based enhancements have shown variability in the input and yield results. This evidence-based study used meta-analysis in determining the performances of iron-based additives on biogas yield. Previously published articles on the subject were systematically identified and compiled based on set inclusion criteria. The database was used to analyze the influence of iron-based additives on the enhancement of biogas yield during anaerobic digestion of organic wastes. The pooled effect estimates at 95% confidence interval was generated with the use of Random-effects model. The overall result of the meta-analysis performed showed that iron-based additives supplementation significantly enhanced biogas yield at Standard mean difference = 1.451, 95% CI: 1.280–1.622, p < 0.001. Restricted subgroup analysis indicated that all the moderators had a significant influence on biogas yield of iron-based treated anaerobic digestion processes at p < 0.001. Evidence of heterogeneity was observed, while meta-regression analysis indicated that most of the sources of heterogeneity were explained by the additive-types, substrate-types, dosage range and research location at p < 0.05. The result of this study showed the potential of iron-based additives supplementation to improve biogas yield during anaerobic digestion of organic wastes. The information from this study avails important suggestions on policy advancements and sustainable usage of iron-based enhanced anaerobic digestion processes in biogas industries.