Abstract
Anaerobic digestion for the valorization of organic wastes into biogas is gaining worldwide interest. Nonetheless, the sizing of the biogas plant units require knowledge of the quantity of feedstock, and their associated methane potentials, estimated widely by Biochemical Methane Potential (BMP) tests. Discrepancies exist among laboratories due to variability of protocols adopted and operational factors used. The aim of this study is to verify the influence of some operational factors (e.g., analysis frequency, trace elements and vitamins solution addition and flushing gas), feedstock conservation and the source of inoculum on BMP. Among the operational parameters tested on cellulose degradation, only the type of gas used for flushing headspace of BMP assays had shown a significant influence on methane yields from cellulose. Methane yields of 344 ± 6 NL CH4 kg−1 VS and 321 ± 10 NL CH4 kg−1 VS obtained from assays flushed with pure N2 and N2/CO2 (60/40 v/v). The origin of inoculum (fed in co-digestion) only significantly affected the methane yields for straw, 253 ± 3 and 333 ± 3 NL CH4 kg−1 VS. Finally, freezing/thawing cycle effect depended of the substrate (tested on biowaste, manure, straw and WWTP sludge) with a possible effect of water content substrate.
Highlights
The effect of trace elements and vitamins in the anaerobic medium was investigated results are in contradiction to the results reported by Koch et al [14,15]
These results suggest that the influence of inoculum source on methane yields is dependent on several factors, such as microbial community and, enzymatic activities within the inoculum, and of the methanogenic ones [19] and the concentration of trace elements and vitamins in the inoculum [9]
Results showed that the type of gas used for flushing headspace of Biochemical Methane Potential (BMP) assays with pure N2 or a mixture N2 /CO2 had showed a significant difference on the methane yields of the studied substrates
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Addition of basic anaerobic medium containing trace elements and vitamins is highly dependent on the inoculum characteristics and/or source [9] Another parameter of significance in BMP assay preparation is the type of gas used to flush the headspace in order to create anaerobic condition in the assays. Use of CO2 in the flushing gas mixture has been shown to increase the methane production [13,14], no such results were noticed in inter-laboratory studies [15,16]. The effect of inoculum source and substrate storage on the methane potential of different organic wastes (i.e., bio-waste, cow manure, straw and WWTP sludge) was evaluated
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