When is a central CO₂ conditioning system beneficial for CCS from biogas?: A techno-economic analysis of capacities and distances

Biogas plants are expected to play an important role in the future global energy system and hold a large potential for achieving negative CO₂ emissions. In Denmark, CO₂ separation is implemented in the majority of biogas plants. Therefore, their CO₂ is readily available, only requiring the subsequent process steps conditioning, transportation, and storage to exploit the biogenic CO₂ for net-negative emissions. However, biogas plants are relatively small point sources, which may result in high CCS deployment costs. Therefore, this study investigates how two biogas plants could economically benefit from sharing a common conditioning system. The technical performance of the processes are evaluated through process modelling and simulation, and a detailed economic analysis is used to evaluate the costs of the system. Four different options with different degrees of centralisation were considered. It was investigated for which emission levels and transport distances a centralised system shared between at least two biogas plants could be relevant. A shared conditioning system was found to yield economic benefits when two plants were located within 5 km to 10 km and when only the liquefaction and purification subprocesses were centralised. The results show that permanent storage of CO₂ from biogas plants can be cost-competitive with other negative emission technologies. Furthermore, an average cost saving of 13 % can be achieved by relevant existing Danish plants when the CO₂ conditioning process is shared between at least two biogas plants.