Chlorine production process can result in discharge of tremendously harmful materials besides it requires high‐energy need, which basically can also lead to additional environmental impacts. This article presents an exergy‐aided life cycle assessment (LCA) to evaluate power generation from natural gas and biomass in the phase of green energy transition to augment the sustainability as much as attainable. A series of statistically discernible scenarios assisted by Monte Carlo Simulation are specified. Results show a reduction in environmental impacts from 2.249E‐02 to 2.180E‐02 MJ‐Eq of nonrenewable energy supplies in accordance with the cumulative exergy demand or from 1.28E‐06 to 7.62E‐07 in accordance with ReCiPe 2008, paving the way toward an environmentally sustainable chlorine production process. LCA is useful to measure the environmental impacts of each chemical constituent accurately, showing that CO2 emitted from this process has much more unfavorable impacts than other harmful materials on human health. Furthermore, LCA discloses that the natural gas could even be less environmentally sustainable than residual fuel oil concerning human toxicity freshwater ecotoxicity, marine ecotoxicity, particulate matter formation, terrestrial acidification, and fossil depletion impacts. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019