Fig. 1: Process diagrams of conventional CCU and BICCU.

A Conventional CCU. B BICCU. The conventional CCU process captures CO₂ by absorbing it in capture agents and utilizes thermal energy for CO₂ desorption. This process is followed by downstream compression and dehydration for storage and transport of the CO₂ to a CO₂ utilization unit of methanation for producing grid injectable CH₄. In contrast, the BICCU process captures CO₂ by absorbing the CO₂ in a capture agent followed by combined microbial-mediated desorption and utilization by using renewable produced H₂ to convert the CO₂ directly into grid-injectable CH₄. The energy balances for both systems are presented, with values expressed as GJ t⁻¹ CO₂ captured. Heat integration for the biomethanation process has not been considered. The numbers in parenthesis represent a scenario where electrolysis has no energy loss. All numbers are sourced from ref. ³⁸.