Techno-economic-environmental assessment framework considering temporal effects for industry parks decarbonization from an energy supply perspective: A chlor-alkali production demonstration case

Industrial parks are critical drivers of economic development but must adopt low-carbon strategies to meet the United Nations' Sustainable Development Goals (SDGs), particularly those related to climate action and sustainable production. Chemical parks, characterized by complex production chains and strong dependence on onsite combined heat and power (CHP) systems, face the challenge of balancing economic performance, environmental benefits, and long-term transition dynamics. This study proposes a techno-economic-environmental assessment framework that explicitly integrates upstream energy supply transitions, product-level carbon allocation, and temporal effects of grid decarbonization and carbon pricing. Using caustic soda production as a representative case, we systematically quantified how allocation principles and co-firing strategies reshape carbon emission distribution across main and co-products, an aspect rarely addressed in existing studies. Product-level carbon intensity of caustic soda ranges from 1.17 to 2.43 kgCO₂eq/kg. Compared with mass-based allocation, molar mass-based allocation induces only minor changes, whereas value-based allocation substantially redistributes emissions, highlighting its sensitivity for high-value co-products. Biomass co-firing at ratios above 60% reduces carbon intensity by up to 23%, while sludge co-firing increases emissions by up to 32%, revealing contrasting environmental outcomes of alternative low-carbon fuels. By introducing temporal effect analysis and carbon price tolerance, the study further quantified the long-term decarbonization limits and economic viability of CHP systems, showing that co-firing provides limited long-term carbon benefits under rising carbon prices, while China's current low carbon price favors CHP deployment. Overall, this work advances a transferable assessment framework to support evidence-based decarbonization pathways for electricity-intensive industrial parks.