Environmental assessment of ethane and associated NGL products from diverse sources: A process-based life cycle approach

Natural gas liquids (NGLs) are critical components in petrochemical and energy supply chains, with ethane playing a central role as a key feedstock for ethylene production. This study presents a comparative environmental assessment of ethane and associated NGL products, propane, butane, and pentane, sourced from major global producers, namely the United States and Saudi Arabia. Five NGL sources (three from the United States and two from Saudi Arabia) are analyzed to capture variations in feedstock composition and processing. The separation process, including the acid gas removal, dehydration, and NGL fractionation, is modeled using UniSim Design, allowing for detailed simulation of energy use and emissions across each separation stage. These simulations provide the basis for a life cycle assessment (LCA), conducted in accordance with ISO 14040/44 standards, and focus on cradle-to-gate system boundaries. A carbon content-based allocation method is applied to allocate environmental burdens among co-products, reflecting the physical basis of product differentiation. The LCA results reveal notable differences in the environmental profiles of NGL products across source regions. Ethane exhibits up to 21 % variation in life cycle emissions intensity depending on origin, influenced by upstream composition and fractionation energy requirements. This study demonstrates the value of integrating process simulation with LCA to evaluate environmental trade-offs in NGL supply chains. The findings support improved transparency in emissions reporting and offer a basis for more sustainable sourcing strategies in downstream petrochemical applications.