Comparative Industrial-Scale Life Cycle Assessment of Base Case and Heat Recovery Scenarios for Carbon Capture from Natural Gas Combined Cycle Power Plants Using Aqueous Ammonia

Abstract

As social and economic activities return to pre-COVID-19 levels, greenhouse gas emissions continue to rise, exacerbating climate change. This study explores carbon capture and sequestration (CCS) technologies to mitigate carbon dioxide (CO₂) emissions from natural gas combined cycle (NGCC) power plants, proposing aqueous ammonia as a solvent due to its high reactivity and lower energy regeneration requirements. A life cycle assessment (LCA) was conducted to compare a base case with a heat recovery scenario for capturing 300 kilotonnes of CO₂ annually from NGCC flue gas. The cradle-to-gate LCA, using a functional unit of 1 tonne of CO₂ input, encompasses the process from flue gas extraction to the production of purified CO₂. The heat recovery scenario outperformed the base case in all environmental impact categories. The LCA results indicated a net carbon abatement of 94.49 kg CO₂ eq for the base case and 508.69 kg CO₂ eq for the heat recovery scenario. Key contributors to global warming potential (GWP) included electricity consumption and heat production, while the human toxicity potential (HTP) and marine aquatic ecotoxicity potential (MAETP) were significant environmental impact categories. Sensitivity analysis and Monte Carlo simulation highlighted critical parameters and uncertainties, and scenario analysis examined additional variables for a comprehensive assessment. Aqueous ammonia not only lowers emissions but also provides cost-effectiveness and high absorption efficiency, positioning it as a viable option for large-scale CO₂ capture. Additionally, it has potential for future integration with the carbonation of municipal and industrial solid waste, contributing to sustainable waste management and carbon sequestration.