Thermodynamic efficiency of carbon capture and utilisation in anaerobic batch digestion process

• Biological carbon capture and utilisation was simulated in a batched anaerobic digestion.
• It was observed overall 29% reduction in pCO2 with 26% compensation of pCH4.
• Anaerobic ammonium oxidising process is strongly related to biological CO2 utilisation.

Carbon capture and storage (CCS) in the oil and water industries is becoming common and a significant consumer of energy typically requiring 150–450 °C and or several hundred bar pressure [1] particularly in geological deposition. A biological carbon capture and conversion has been considered in conventional anaerobic digestion processes. The process has been utilised in biological mixed culture, where acetoclastic bacteria and hydrogenophilic methanogens play a major key role in the utilisation of carbon dioxide. However, the bio catalytic microorganisms, hydrogenophilic methanogens are reported to be unstable with acetoclastic bacteria. In this work the biochemical thermodynamic efficiency was investigated for the stabilisation of the microbial process in carbon capture and utilisation. The authors observed that a thermodynamic efficiency of biological carbon capture and utilisation (BCCU) had 32% of overall reduction in yield of carbon dioxide with complimentary increase of 30% in yield of methane, while the process was overall endothermic. Total consumption of energy (≈0.33 MJ l−1) was estimated for the carbonate solubility (0.1 mol l−1) in batched BCCU. This has a major influence on microbial composition in the bioreactor. This thermodynamic study is an essential tool to aid the understanding of the interactions between operating parameters and the mixed microbial culture.

Relative energy consumption versus reaction coordinate of CCU in anaerobic brewery sludge digestion in case of over saturated carbonates (>0.1 mol l−1); where volatile fatty acids are acetic (HAc), propionic (Hprop) and butyric (HButy).Figure optionsDownload as PowerPoint slide