Integrating biogas in regional energy systems to achieve near-zero carbon emissions

Abstract

Recent years have witnessed an increasing proliferation of biomass technologies since biomass is recognized as a natural carbon-neutral fuel. Existing studies have paid extensive attention to the concept and modeling of zero-carbon energy systems or buildings. However, few studies have explored the multi-energy coupling method and techno-economic evaluation of biomass to achieve near-zero carbon systems. Therefore, we propose an optimal sizing framework for integrating waste-to-biogas in regional energy systems to achieve near-zero carbon emissions. To establish energy balance between supply and demand and regional self-sufficiency, biomass is added to the existing natural gas energy framework. Biomass produces biogas through anaerobic digestion reactions, and the biogas output can be constructed as an analytical function related to the anaerobic reaction environment temperature and reactant volume. Furthermore, this paper constructs a planning model with the goal of minimizing the investment and operating costs of biomass, solar and storage, respecting carbon emission constraints induced by local electricity and gas energy flows. The impact of carbon emission regulations on the investment of each component of the energy system is determined using a sensitivity analysis of carbon emissions. To solve the nonlinearity issues of the biogas production function, we propose a convexification method based on least squares fitting. Case studies based on realistic datasets demonstrate that, under the constraints of carbon emissions, the integration of biogas can significantly improve the supply adequacy of the energy system, reduce investment costs by up to 77.07%, and carbon emission reduction intensity is 5.11 kg CO2 kg-1 Biogas, all while lowering the Levelized Cost of Energy (LCOE). In comparison to prior research, the model provided in this paper more accurately portrays the biogas production process, lowers the system investment cost and LCOE, and emphasizes the benefits of biomass.