This paper critically reviews the impacts of supplementing trace elements on the anaerobic digestion performance.
The in-depth knowledge of trace elements as micronutrients and metalloenzyme components
justifies trace element supplementation into the anaerobic digestion system. Most of the earlier studies
reported that trace elements addition at (sub)optimum dosages had positive impacts mainly longer term
on digester stability with greater organic matter degradation, low volatile fatty acids (VFA) concentration
and higher biogas production. However, these positive impacts and element requirements are not fully
understood, they are explained on a case to case basis because of the great variance of the anaerobic
digestion operation. Iron (Fe), nickel (Ni) and cobalt (Co) are the most studied and desirable elements.
The right combination of multi-elements supplementation can have greater positive impact. This measure
is highly recommended, especially for the mono-digestion of micronutrient-deficient substrates.
The future research should consider the aspect of trace element bioavailability.