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International audience; Biogas production via anaerobic digestion could approach thermal autarky (less biogas self-consumption and better energy efficiency) using enhanced solutions for thermal insulation based on new multimembrane gasholder configurations, loss avoidance, and heat recovery strategies. In this study, a predictive and configuration-dependent dynamics energy model is developed to daily and seasonally assess the thermal efficiency and heating requirements of industrial biogas plants involving wet digesters with upper multimembrane gasholders. The model is validated using experimental data from a full-scale biogas plant in operation over a one-year period.The energy model involves a set of dynamic energy balances defined for each compartment of the digester and gasholder. All possible heat sources and sinks (ambient air temperature, wind, rain, and solar radiation) and heat exchanges or losses via advection, convection, and conduction, as well as a complete representation of the infrared radiative networks between the surfaces of the digester, are included for each compartment depending on the operating and design parameters. These heat exchanges are subject to fluctuating environmental conditions (e.g., ambient air temperature, wind, rain, and solar radiation).The results indicate that triple-membrane gasholders with a third insulation membrane made of a suitable material and thickness, together with the involvement of heat recovery from the digestate advective heat, are capable of reducing the overall thermal losses by more than 95 % (e.g., −51 % of the gasholder cover loss and − 81 % of the advective digestate loss) and when the waste heat from biogas purification is also valorized, the biogas plant can become thermally self-sufficient.

International audience; In a circular economy approach, heterogeneous wastes can be upgraded to energy in the form of syngas via pyrogasification, and then to methane via biomethanation. Working at high pressure is a promising approach to intensify the process and to reduce gas-liquid transfer limitations. However, raising the pressure could lead to reaching the CO inhibition threshold of the microorganisms involved in syngas-biomethanation. To investigate the impact on pressure on the process, a 10L continuous stirred tank reactor working at 4 bars and 55 °C was implemented. Syngas (40% CO, 40% H2, 20% CO2) biomethanation was performed successfully and methane productivity as high as 6.8 mmolCH4/Lreactor/h with almost full conversion of CO (97%) and H2 (98%) was achieved. CO inhibition was investigated and carboxydotrophs appeared less resistant to high CO exposition than methanogens.

This paper deals with the control of the start-up phase in anaerobic digestion systems by using monitoring parameters already implemented that have been coupled to the control law. Methane yield, as well as methane flow rate, and the ratio of intermediate over total alkalinity have been used as control parameters. These measurements have been included in a switching control strategy to drive the process toward a steady state in which biogas production is optimized avoiding accumulation of volatile fatty acids. Experimental validation of this control strategy has been performed from the results obtained using a 358 litter fixed bed anaerobic digester treating industrial winery wastewater.