Life cycle carbon footprint and water footprint analysis of solar energy to ethylene glycol

Ethylene glycol (EG), the simplest diol with broad applications in the chemical industry, demonstrates promising prospects. This study systematically evaluates the water footprint (WF) and carbon footprint (CF) of a novel solar high-temperature pyrolysis process for EG production (StEG) within a life cycle framework for the first time, comparing with coal-to-EG process (CtEG). The StEG process comprises three routes: solar-driven high-temperature pyrolysis of CO2 (SCtEG), H2O (SHtEG) and CO2-H2O mixtures (SC-HtEG). Results show that under baseline conditions, the WF for SCtEG, SHtEG, SC-HtEG and CtEG are 2684.27 L H2O/t-EG, 4225.65 L H2O/t-EG, 2587.46 L H2O/t-EG and 4191.11 L H2O/t-EG, with corresponding CF of −188.23 kg-CO2/t-EG, −114.95 kg-CO2/t-EG, −222.7 kg-CO2/t-EG and 1161.32 kg-CO2/t-EG. The EG synthesis stage emerges as the dominant contributor to direct WF (DWF) and direct CF (DCF), while electricity consumption constitutes the primary component of indirect WF (IWF) and indirect CF (ICF). Sensitivity analysis of 20 scenarios showed that an increase or decrease of ±10 % in EG production efficiency had the greatest impact on WF and CF. The impact of WF and CF of 31 provinces in China under different energy mixes was also explored. The ICF of Sichuan, Yunnan, and Qinghai were far lower than the baseline scenario, while the IWF was the opposite. These findings provide critical insights for advancing energy conservation, emission reduction, and cleaner production in future EG production.