Steering Product Formation in High-Pressure Digestion Systems

Anaerobic Digestion is a widely used and advantageous technology for wastewater treatment, since besides organic material degradation, biogas is produced (van Lier et al. 2008). Using conventional technology, the methane content reaches 50-75% (IEA Bioenergy, 2009). Previous proof-of-principle research has demonstrated the feasibility of using Autogenerative High Pressure Anaerobic Digestion (AHPD) to produce biogas with improved quality (90-95% CH₄ content) and at a pressure suitable for high-grade use (Lindeboom, 2014a). Furthermore, AHPD has also proved to produce other metabolites (carboxylates), that by themselves or through further conversion, could be interesting for the chemical industry. New insights into waste to bioproduct conversion have established that economically-attractive end-products can be obtained with mixed cultures and complex substrates (Agler et al., 2011). In this context, High-Pressure Anaerobic Digestion (Hi-PAD) offers some interesting features. Based on previous work, it is expected that specific pressure effects influence the kinetics and thermodynamics of mixed culture fermentations (e.g. role of the CO₂ partial pressure). This project aims to further address these effects and determine to what extent they can be exploited to improve the fermentation yield and selectivity.