Effect of Natural Mineral on Methane Production and Process Stability During Semi-Continuous Mono-Digestion of Maize Straw

Abstract

The effect of natural mineral on the mono-digestion of maize straw was evaluated in continuously stirred tank reactors (CSTRs) at 38 °C. Different strategies of mineral addition were studied. The organic loading rate (OLR) was varied from 0.5 to 2.5 g volatile solid (VS) L(-1) d(-1). A daily addition of 1 g mineral L(-1) in reactor 2 (R2) diminished the methane production by about 11 % with respect to the initial phase. However, after a gradual addition of mineral, an average methane yield of 257 NmL CH4 g VS(-1) was reached and the methane production was enhanced by 30 % with regard to R1. An increase in the frequency of mineral addition did not enhance the methane production. The archaeal community was more sensitive to the mineral than the bacterial population whose similarity stayed high between R1 and R2. Significant difference in methane yield was found for both reactors throughout the operation.

Bioavailability and dosing strategies of mineral in anaerobic mono‐digestion of maize straw

“…The experiments were performed in two 1-L (0.8 L effective volume) CSTRs as described by González-Suárez et al [11] for a period of 117 days of investigation. The reactors were operated under mesophilic conditions at a temperature of 37 ± 1°C.…”

“…Volumetric biogas production was continuously measured online with a Ritter Milligas Counter (Ritter, Germany) and methane content of biogas was determined using a gas chromatographic analysis (Shimadzu GC-2010) as described González-Suárez et al [11]. Volumetric biogas production was continuously measured online with a Ritter Milligas Counter (Ritter, Germany) and methane content of biogas was determined using a gas chromatographic analysis (Shimadzu GC-2010) as described González-Suárez et al [11].…”

“…Feeding was carried out once a day with amounts of the feedstock (according to the applied OLR) and mineral previously defined. Volumetric biogas production was continuously measured online with a Ritter Milligas Counter (Ritter, Germany) and methane content of biogas was determined using a gas chromatographic analysis (Shimadzu GC-2010) as described González-Suárez et al [11]. The maximum expected methane yield from maize straw was obtained by a modified biochemical methane potential (BMP) test (data not shown) according to Pagés et al [13].…”

“…Others research on trace elements supplementation in mono-digestion of straw and silage with the goal to enhance the performance and stability of the process [2,3,5]. 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]. The previous data resulted from addition of trace metals in form of salts.…”

“…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.…”