How sustainable was ancient Roman concrete?

The remarkable longevity of Roman concrete has long fascinated researchers and hinted at its potential as a sustainable alternative to modern concrete formulations. However, rigorous assessment of its environmental impact-particularly in the context of modern production technologies-has been lacking. Here, we follow the life cycle assessment methodology to systematically quantify the impacts of various Roman concrete formulations relative to modern technologies. Our findings reveal nuanced insights into the sustainability prospects of Roman concrete, shedding light on its greenhouse gas emissions, energy demand, particulate matter emissions, and water utilization. Contrary to initial expectations, adopting Roman formulations with current technology may not yield substantial reductions in emissions or energy demand unless used in conjunction with other decarbonization advancements. Nonetheless, our findings underscore the importance of Roman practices, particularly the reliance on biomass as a fuel source, which presents opportunities for decarbonizing modern cement production.