Trace element requirements of agricultural biogas digesters during biological conversion of renewable biomass to methane

► The availability of trace metals plays a very significant role on the performances of agricultural biogas digesters operated with biomass. ► Poor performance efficiency without any obvious reason should be related to unavailability of trace metals. ► This article presents an overview of research studies carried out on trace metal requirements of anaerobic digesters operated with biomass. ► Use of advanced molecular biology techniques could help in understanding the trace element requirements of Archaea.