Footprint family of China's coal-based synthetic natural gas industry

China's increasing demand for natural gas and concerns related to energy security have expanded the coal-based synthetic natural gas (CBSNG) industry. The accompanying intensive environmental and economic impacts are evaluated based on static design or simulated data, but their industrialized performance at both the project-specific and national levels remains unclear. The objective of this study is to estimate an energy-water-pollutant-carbon-economic footprint family of China's CBSNG industry. To this end, a comprehensive accounting methodology for the multiple footprints of CBSNG was developed and the first-hand dynamic operation and economic data of four commercialized projects were surveyed. Accompanied by the technology learning curve, scenarios towards 2035 were designed to predict future trajectories of these footprints. The results show that the project-specific energy-water-pollutant-carbon footprints generally reduced by 10–30 % from 2020 to 2022, while the economic footprints increased slightly. The total energy-water-pollutant-carbon footprints, driven by scale expansion, increased by less than 10 % and the total economic footprint increased by over 30 %. They were predicted to approximately double by 2025 and increase fivefold by 2035, which suggests the deployment of green hydrogen and a circular economy, optimization of spatial layout, and fortification of separate statistics and economic policies for sustainability.