From biogas upgrading to CO2 utilization and waste recycling: A novel circular economy approach

Herein a novel process to synergize biogas upgrading, CO2 utilization and waste recycling is proposed. Our study emerges as a promising strategy within the circular economy. In this work, the technical feasibility of Flue-Gas Desulfurization Gypsum as precipitant for definitely CO2 storage is studied. The precipitation stage is evaluated through two key factors: the quality of the carbonate product and the precipitation efficiency obtained. The physicochemical characterization of the solid carbonate product was analysed by means of Raman, X-Ray diffraction and scanning electron microscopy. The precipitation efficiency is evaluated through the variation of the main precipitation parameters (temperature, molar ratio and time). For this purpose, two groups of experiments were performed. The first group was aimed to model the precipitation system through experiments designed with DesignExpert vs.12 software. The second group of experiments allows to compare our results with pure species as precipitants, as well as to validate the model designed. The physicochemical characterization performed reveals high purity calcite as product. Encouraging precipitation efficiencies were obtained, ranging from 53.09–80.09% (66 % average). Furthermore, the model reveals a high influence of the molar ratio (3–5 times higher impact than other parameters) and low influence of temperature, which evidences the low energy consumption of the proposal. To optimize energy consumption, the model suggests 33 sets of parameters values. Examples of these values are 20 °C, 1.5 mol/mol, and 30 min, which allow to obtain a 72.57 % precipitation efficiency. Overall, this study confirms the technical feasibility of this circular economy approach