Carbon Capture and Utilization via Green Ammonium Bicarbonate Production: A Process Modeling and Economic Analysis

Kurzfassung

The Chilled Ammonia Process (CAP) has emerged as a promising post-combustion carbon capture (CC) technology, offering high CO₂ capture efficiency (>90 mol.%) with lower regeneration energy requirements compared to conventional monoethanolamine (MEA)-based systems (Darde et al. 2010). CAP utilizes an aqueous ammonia solution to chemically absorb CO₂ at low temperatures (5-15 °C), forming ammonium bicarbonate (NH₄HCO₃, ABC) as the primary reaction product. This work presents a novel departure from traditional CAP configurations by diverting the CO₂-rich ammonia solution from the absorber bottom directly to a crystallization unit for the recovery of solid ABC. While methodologies devised for the optimized production of ABC exist, they rely on the supply of high-quality CO2, while not addressing flue gas capturing (Zhuang et al. 2012). Preliminary modeling results suggest that the concentration of CO₂ in the ammonia-rich solution is the most critical factor for ABC production, and that the uncrystallized solution contains significantly less CO₂ compared to the traditional CAP configuration. The uncrystallized lean solution is regenerated, makeup water and ammonia are added, and the regenerated stream is recycled back to the absorber. (Zhuang et al. 2012) This approach not only greatly diminishes the high energy penalty associated with solvent stripping but also transforms captured CO₂ into a valuable commodity – ammonium bicarbonate – thereby enabling carbon utilization (CCU) within a circular economy framework. Ammonium bicarbonate is a well-known chemical with applications in the food, pharmaceutical, and agricultural sectors. As a fertilizer, ABC offers several agronomic advantages over urea: it releases bioavailable NH₄⁺ ions without generating inhibitory levels of ammonia in soil, enhances local CO₂ concentrations near plant roots to stimulate photosynthesis, and exhibits lower groundwater contamination potential (Luo et al. 2025; Mühlbachová et al. 2021). Despite its lower nitrogen content (17 wt.%), ABC’s environmental profile and soil compatibility make it an attractive “green” alternative, particularly in sustainable agriculture. However, industrial production of ABC typically relies on synthetic ammonia derived via the Haber-Bosch process—a highly energy-intensive route responsible for around 2.4 ton CO₂ per ton of NH₃ produced—undermining its sustainability credentials. This study introduces a fully integrated process model developed in Aspen Plus®, based on operational data from a 1.7 MWe Process Development Unit (PDU) operated by the Electric Power Research Institute (EPRI) in collaboration with Alstom (now GE Steam Power) (EPRI 2011); the data used refers to the period of June to September 2009. The PDU achieved a 90 mol.% CO₂ capture rate from pulverized coal flue gas using CAP. Our model extends beyond capture by incorporating downstream crystallization, solvent recycle with water washing to minimize NH₃ emissions, and integration with a green ammonia production system powered by renewable electricity. Green ammonia synthesis includes air separation (via pressure swing adsorption, PSA), water electrolysis for H₂ production, and Haber-Bosch synthesis using electric compression—enabling near-zero-emission ammonia feedstock. The primary objective of this work is to evaluate the technical feasibility and economic viability of producing "green ABC" using captured CO₂ and renewable hydrogen-based ammonia. We conduct a detailed mass and energy balance analysis, estimate capital and operating costs, and compare the levelized cost of ABC production via this integrated pathway against conventional manufacturing routes. This work fills a critical research gap in the intersection of carbon capture and green fertilizer production, proposing a synergistic pathway that aligns decarbonization goals with sustainable agriculture, offering a scalable CCU solution with co-benefits in food security and soil health. By valorizing captured CO₂ into a high-demand chemical, the proposed concept enhances the economic outlook of carbon capture technologies while supporting the transition to a low-carbon circular economy.