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This study aimed at studying the biomethanation process using a 100 L pilot-scale digester equipped with a dense membrane for hydrogen injection. Hydrogen mass transfer was characterized and the impact of hydrogen flowrate, agitation rate and of the co-injection of CO 2 , on biogas production and composition, was precisely studied. A linear relationship between H 2 flowrate and the CO 2 and CH 4 rates in biogas was found but no impact on biogas flowrate was shown. It was also noticed that, without exogenous CO 2 injection, and for high H 2 injection flowrates, residual H 2 could be found at the digester outlet due to local CO 2 limitation. Thus, this study suggested that biogas production in biomethanation process at the pilot scale was probably rather limited by the dissolved CO 2 transport within the liquid phase than by the hydrogen mass transfer itself., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

We described mathematically the process of peat methanization in a boreal mesotrophic fen. Gaseous and dissolved CH 4 and CO 2 as well as their δ 13 C signatures were considered in the dynamic equations for incubation bottles. In accordance with the model, acetate, H 2 , and CO 2 were produced during cellulose hydrolysis and acidogenesis. 13 C/ 12 C in CO 2 was a key variable reflecting dynamic changes in the rates of cellulose hydrolysis and acidogenesis, acetoclastic and hydrogenotrophic methanogenesis. As CO 2 is the substrate in hydrogenotrophic methanogenesis, δ 13 C-CO 2 increased from the start till the dissolved hydrogen concentration became very low. Thereafter, the rate of acetoclastic methanogenesis with the significant current acetate concentration dominated over the rate of hydrogenotrophic methanogenesis leading to the decreasing δ 13 C-CO 2 and the increasing δ 13 C-CH 4 . The model was validated by describing the system's dynamics under strong and weak inhibition of acetoclastic and hydrogenotrophic methanogenesis by methyl fluoride, respectively. During peat methanization at the lowered temperature of 10 °C, the processes of hydrogenotrophic methanogenesis and homoacetogenesis competing for H 2 may occur. However, based on dynamics of the carbon isotope signatures, especially on dynamics of δ 13 C-CO 2 , the model showed no significant contribution of homoacetogens in peat methanization.

A wide variety of inhibitors can induce anaerobic digester disruption. To avoid performance losses, support media can be used to mitigate inhibitions. However, distinguishing the physico-chemical from the biological mechanisms of such strategies remains delicate. In this framework, the impact of 10  g/L of different types of zeolites and activated carbons (AC) on microbial community dynamics during anaerobic digestion of biowaste in the presence of 1.3 g/L of phenol was evaluated with 16 S rRNA gene sequencing. In the presence of AC, methanogenesis inhibition was rapidly removed due to a decrease of phenol concentration. This abiotic effect related to the physico-chemical properties of AC led to increased final CH4 and CO2 productions by 29-31% compared to digesters incubated without support. Interestingly, although zeolite did not adsorb phenol, final CH4 and CO2 production reached comparable levels as with AC. Nevertheless, compared to digesters incubated without support, methanogenesis lag phase duration was less reduced in the presence of zeolites (5 ± 1 days) than in the presence of activated carbons (12 ± 2 days). Both types of support induced biotic effects. AC and zeolite both allowed the preservation of the major representative archaeal genus of the non-inhibited ecosystem, Methanosarcina. By contrast, they distinctly shaped bacterial populations. OTUs belonging to class W5 became dominant at the expense of OTUs assigned to orders Clostridiales, Bacteroidales and Anaerolinales in the presence of AC. Zeolite enhanced the implantation of OTUs assigned to bacterial phylum Cloacimonetes. This study highlighted that supports can induce biotic and abiotic effects within digesters inhibited with phenol, showing potentialities to enhance anaerobic digestion stability under disrupting conditions., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Slaughterhouses generate highly polluted effluents, and if not treated before discharge can cause major adverse environmental and public health impacts. Treatment of this waste by anaerobic digestion can reduce those impacts while producing a potentially valuable source of energy. The purpose of this study was to investigate this process efficiency under pilot operating conditions for a more accurate scaling up. Blood waste from a slaughterhouse was treated in a pilot‐scale digester of 30 dm3 total volume under mesophilic temperature conditions. Operating parameters such as pH, alkalinity, organic loading, volatile fatty acids, biogas composition, total and volatile solids were monitored in order to study the behavior of the fermentation process. The results show that no significant inhibition were caused by the accumulation of volatile fatty acids, due to the high buffering capacity of treated sludge. An efficient reduction of organic matter was obtained with a COD decrease of about 67% within 40 days of fermentation. The biogas produced was of a good quality with high CH4 yields (above 70%) and low CO2 yields, corresponding to a biomethane potential of 225.9 dm3 CH4/kg TVS. Logistic model described accurately the methane production kinetic and enables an easy process scaling up for industrial applications. [ABSTRACT FROM AUTHOR]

Abstract: Clear economic advantages may be obtained from the management of seasonal fruit wastes by codigestion at existing facilities which are working throughout the year with other residues. We have explored the biomethanization of pear residues in a 5L stirred reactor loaded with sludge from the anaerobic digester of a municipal wastewater treatment plant. Different organic loading rates (OLRs) of fruit waste were tested with two delivery procedures: a discontinuous one (fed once a day) and a pseudocontinuous one. For both procedures, as the OLR increases the pH of the digester drops to acidic values and large OLRs may cause the reactor failure. Nevertheless, the pseudocontinuous delivery allows the treatment of more residue, (10.5 versus 6.0g of volatile solids per litre of reactor and day), maintaining the specific biogas production (0.44L of biogas per gram of volatile solids), with some improvement in methane concentration (44% vs 39%). [Copyright &y& Elsevier]

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