The feasibility of trace element supplementation for stable operation of wheat stillage-fed biogas tank reactors.

The aim of this study was to investigate the effect of trace element supplementation on operation of wheat stillage-fed biogas tank reactors. The stillage used was a residue from bio-ethanol production, containing high levels of sulfate. In biogas production, high sulfate content has been associated with poor process stability in terms of low methane production and accumulation of process intermediates. However, the results of the present study show that this problem can be overcome by trace element supplementations. Four lab-scale wheat stillage-fed biogas tank reactors were operated for 345 days at a hydraulic retention time of 20 days (37 degrees C). It was concluded that daily supplementation with Co (0.5 mg L(-1)), Ni (0.2 mg L(-1)) and Fe (0.5 g L(-1)) were required for maintaining process stability at the organic loading rate of 4.0 g volatile solids L(-1) day(-1).