The minimum requirements for nickel and cobalt as trace metals in thermophilic biogas fermentation of palm oil mill effluents

Abstract

This paper reports the minimum requirements of nickel and cobalt as trace metals in the formation of biogas from the digestion of palm oil mill effluent (POME). Anaerobic digestion was conducted in a two-liter continuous stirred tank reactor (CSTR) and operated at a thermophilic condition of 55 oC. As raw material, a non-treated liquid waste from the mills was used. Hydraulic retention time (HRT) of the digesters was preserved at six days.The results come to the conclusion that the decrease of trace metals concentration didn’t influence the total solid, volatile solid concentration and also M-alkalinity. Based on the analyzed parameter, the reduction of trace metals concentration up to 97% of the initial nickel and cobalt concentration, 0.49 and 0.42 mg/L for nickel and cobalt, still allows the fermentation to obtain optimum biogas production, where the 90% reduction of trace metals produced the average volume of biogas 10.5 L/day at the rate of VS degradation 52-53%.