A Circular Economy Perspective: Recycling Wastes through the CO2 Capture Process in Gypsum Products. Fire Resistance, Mechanical Properties, and Life Cycle Analysis

In recent years, the implementation of CO2 capture systems has increased. To reduce the costs and the footprint of the processes, different industrial wastes are successfully proposed for CO2 capture, such as gypsum from desulfurization units. This gypsum undergoes an aqueous carbonation process for CO2 capture, producing an added-value solid material that can be valorized. In this work, panels have been manufactured with a replacement of (5 and 20%) commercial gypsum and all the compositions kept the water/solid ratio constant (0.45). The density, surface hardness, resistance to compression, bending, and fire resistance of 2 cm thick panels have been determined. The addition of the waste after the CO2 capture diminishes the density and mechanical strength. However, it fulfills the requirements of the different European regulations and diminishes 56% of the thermal conductivity when 20%wt of waste is used. Although the CO2 waste is decomposed endothermically at 650 °C, the fire resistance decreases by 18% when 20%wt. is added, which allows us to establish that these wastes can be used in fire-resistant panels. An environmental life cycle assessment was conducted by analyzing a recycling case in Spain. The results indicate that the material with CO2 capture waste offers no environmental advantage over gypsum unless the production plant is located within 200 km of the waste source, with transportation being the key factor.