“…The previous data resulted from addition of trace metals in form of salts. However, in recent studies, the trace metals supply from natural mineral has demonstrated to have a similar effect during the biodegradation of microcrystalline cellulose (synthetic model substrate) and maize straw in batch and semi-continuous experiments, respectively [10,11]. From their findings, the highest methane yield of 397 and 257 mL CH 4 g −1 VS, were obtained in the AD of microcrystalline cellulose and maize straw, respectively, with mineral addition, which was 31% higher than that the substrates without mineral supply.…”