Author(s): Saba Aghdam Tabar; Usman Safder; Recep Kaan Dereli; Sarah Cotterill; Eoin Casey
Linked Author(s): Usman Safder
Keywords: Biological biogas upgrading Anaerobic digestion Renewable energy Green hydrogen Curtailment BSM2
Abstract: The global push for renewable energy has led to the increasing challenge of energy curtailment, where surplus renewable energy is wasted due to supply-demand imbalances. At the same time, biogas, a renewable energy source, often requires upgrading due to its low methane content and impurities that limit its grid injection. This study investigates the use of surplus renewable energy for hydrogen production and biogas upgrading as a dual solution to both mitigate energy curtailment and enhance biogas quality. Anaerobic Digestion Model No. 1 (ADM1), within Benchmark Simulation Model No. 2 (BSM2), is modified to simulate hydrogen injection into the digester. The modified model is capable of accommodating both variable and constant energy inputs, enabling comparisons to assess the impact of surplus energy variability on anaerobic digester performance and to contrast ideal versus realistic conditions for hydrogen injection. The effect of a hydrogen storage system was evaluated to examine the impact on mitigating surplus energy fluctuations. To determine the optimal conditions for utilising surplus renewable energy while upgrading biogas, various scenarios were simulated with variations in energy availability, the presence of a storage system, and CO2 control strategies. The results demonstrated significant improvements in methane (CH4) content, reaching up to 89% under unlimited energy conditions, compared to 62% in the baseline BSM2 scenario. When excess renewable energy was synchronised with the grid, methane content still reached 86% with PI control and hydrogen storage, despite fluctuations in surplus energy availability. Energy recovery rates of over 50% were achieved by converting surplus energy into biogas. This paper provides insights into the feasibility of surplus renewable energy utilisation through biogas upgrading with the overall aim of climate change mitigation.
Year: 2025