Techno-economic and life cycle environmental assessments of CO2 utilization for value-added precipitated calcium carbonate and ammonium sulfate fertilizer co-production

Abstract

An advanced CO₂ mineralization technology using Flue Gas Desulfurization (FGD) byproduct gypsum, which coproduces value-added precipitated calcium carbonate (precipitated CaCO₃, PCC) and ammonium sulfate [(NH₄)₂SO₄, AS] fertilizer, is being developed to address the technical challenges of achieving simultaneous CO₂ capture and utilization, high CO₂ and calcium conversion, and enhanced energy efficiency. This study aimed to conduct a techno-economic analysis (TEA) and a life cycle assessment (LCA) for this technology. In the TEA, mass and energy balances for CO₂ mineralization integrated with a power plant to utilize all FGD gypsum and approximately 51,000 tonne/year of CO₂ in flue gas were developed through modeling. Major equipment was selected and sized, followed by capital and operating cost analyses. Energy efficiency was improved through the integrated use of both low-grade steam and vacuum from the power plant steam cycle. TEA results revealed that this process was profitable, with a levelized net profit of $328.4 per tonne of CO₂ utilized. The LCA was performed as a cradle-to-gate study for comparative assessments of global warming potential (GWP) and other environmental impacts between the CO₂ mineralization system (i.e., Proposed Production System or PPS) and the conventional processes (i.e., Comparison Production System or CPS). The PPS resulted in a GWP impact of 0.85 kg CO₂-Eq per 1 kg of primary PCC production and 1.32 kg of byproduct AS production, approximately 64 % lower than that of the CPS. The LCA results for other environmental impacts also consistently showed impacts 35–88 % lower for the PPS compared to the CPS.