Dynamic analysis of sustainable biogas-combined-cycle plant: Time-varying demand and bioenergy with carbon capture and storage

Anaerobic-digestion degrades organic wastes, producing biogas to drive bioenergy turbines reducing fossil-fuel dependence. This work evaluates the biogas chain fromwaste-to-bioenergy, using models for dynamic simulation of biogas processing, bioenergy generation, and carbon capture. To do this, a dynamic anaerobic digestion model from the literature was expanded to implement dependence on time-varying external temperature and feedstock conditions and to introduce aspects of transient power plants with time-dependent electricity demand. Results demonstrate that external temperature and feedstock oscillations promote dynamic cycles in biogas production which have to be handled in a dynamic biogas-combined-cycle power plant with post-combustion carbon capture to match costs and transient electricity demand. Consequently, dynamic biogas-storage and bioenergy-storage were implemented to cope with demand/production fluctuations. Bioenergy-storage is accomplished via compressed-air-storage during electricity surplus periods to drive pre-heated turboexpanders during deficit periods. The biogas-combined-cycle, without carbon capture and bioenergy-storage, achieves 15 years of payback-time and 2.6 MMUSD net value. On the other hand, the sustainable configurations with/without bioenergy storage – both bioenergy with carbon-capture and storage systems achieving 1030 kg/h of negative emissions – reach feasibility for CO2 prices of 75 USD/tCO2 attaining net values of 2.02 and 0.18 MMUSD with 21 and 31 years of payback-time respectively.This implementation demonstrates that bioenergy storage with carbon negative emissions is feasible for small-scale biogas-fired combined-cycle plants.