Steering the product spectrum in high-pressure anaerobic processes: CO₂ partial pressure as a novel tool in biorefinery concepts

Background: Elevated CO₂ partial pressure (pCO₂) has been proposed as a potential steering parameter for selective carboxylate production in mixed culture fermentation. It is anticipated that intermediate product spectrum and production rates, as well as changes in the microbial community, are (in)directly influenced by...

Steering Product Formation in High-Pressure Anaerobic Digestion Systems: The role of elevated partial pressure of carbon dioxide (pCO2)

Anaerobic processes such as Anaerobic Digestion (AD) and mixed culture fermentation (MCF) are important technologies in the bioeconomy context since they can be used to convert (waste) biomass feedstock into gaseous energy carriers and chemical commodities, theoretically without the use of any additional energy source. AD is a multi-step...

Modelling of autogenerative high-pressure anaerobic digestion in a batch reactor for the production of pressurised biogas

Background: Pressurised anaerobic digestion allows the production of biogas with a high content of methane and, at the same time, avoid the energy costs for the biogas upgrading and injection into the distribution grid. The technology carries potential, but the research faces practical constraints by a.o. the capital investment needed in high...

Pre-incubation conditions determine the fermentation pattern and microbial community structure in fermenters at mild hydrostatic pressure

Fermentation at elevated hydrostatic pressure is a novel strategy targeting product selectivity. However, the role of inoculum history and cross-resistance, that is, acquired tolerance from incubation under distinctive environmental stress, remains unclear in high-pressure operation. In our here presented work, we studied fermentation and...

Directional Selection of Microbial Community Reduces Propionate Accumulation in Glycerol and Glucose Anaerobic Bioconversion Under Elevated pCO₂

Volatile fatty acid accumulation is a sign of digester perturbation. Previous work showed the thermodynamic limitations of hydrogen and CO₂ in syntrophic propionate oxidation under elevated partial pressure of CO₂ (pCO₂). Here we study the effect of directional selection under increasing substrate load as a...

Improvement of Biogas Quality and Quantity for Small-Scale Biogas-Electricity Generation Application in off-Grid Settings: A Field-Based Study

Small-scale electrical power generation (<100 kW) from biogas plants to provide off-grid electricity is of growing interest. Currently, gas engines are used to meet this demand. Alternatively, more efficient small-scale solid oxide fuel cells (SOFCs) can be used to enhance electricity generation from small-scale biogas plants. Most...

Direct and Indirect Effects of Increased CO₂ Partial Pressure on the Bioenergetics of Syntrophic Propionate and Butyrate Conversion

Simultaneous digestion and in situ biogas upgrading in high-pressure bioreactors will result in elevated CO2 partial pressure (pCO2). With the concomitant increase in dissolved CO2, microbial conversion processes may be affected beyond the impact of increased acidity. Elevated pCO2 was reported to affect the kinetics and thermodynamics of...