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Trace elements (TEs) supplementation to an anaerobic digester provides the necessary bio-catalysis required for process resilience against perturbations that induce decline in efficiency during methanization. The need for TEs supplementation is obvious from the poor TEs balance and low concentrations of nickel (Ni), cobalt (Co), selenium (Se) and molybdenum (Mo) in substrates commonly used for methanization. Co and Se are particularly limiting in methanization substrates. Complex substrates such as grease trap residues, blackwater and sludges have large reservoirs of TEs, but in rather unbalanced composition. Balance in TEs composition and concentrations are important and resulted in average of 50% increase in the methanization processes of substrate degradation and methane formation in mesophilic operation. Lower proportions of methanization enhancement were achieved in thermophilic condition. Volatile fatty acids (VFAs) concentration determines the extent of TEs influence and the significance of TEs interactions during methanization. TEs supplementation based on VFAs concentration offers the most significant methanization enhancement. The TEs mixture that is optimized for different methanization phases also produced comparable enhancement, but with specific weaknesses. Generally, TEs supplementation enhanced microbial substrate affinity in thermophilic systems and microbial maximum substrate conversion rate in mesophilic systems. Significant change in microbial population due to TEs supplementation was not observed during methanization. Bioavailability of TEs during methanization is influenced by TEs adsorption to digester solids. Ni and Co have about 40 - 60% bioavailability; and TEs mixture composition influenced the bioavailability of Ni and Co, but not Se and Mo. Se has about 60% bioavailability and Mo is about 60% bio-unavailable. The quality of methanization digestate regarding TEs content was not compromised due to TEs supplementation. Optimum supplementation range for Ni is below the legal limits set by both the European Directive 86/278/EEC and the German adoption of the European Directive for total Ni concentration in methanization sludge intended for use in soil amendment. There are no such limits for Co, Se and Mo in digestate but optimum concentrations of Ni, Co, Se and Mo for methanization, and their respective levels in digestate are in similar ranges.