Making Roman concrete produces as much CO2 as modern concrete

Martinez et al. analyzed three Roman concrete recipes using different slaked lime-to-pozzolan ratios, measuring greenhouse gas and air emissions during production. Roman concrete's emissions of CO2 per volume rival those of modern concrete, but it results in significantly lower nitrogen oxide and sulfur oxide emissions. Roman concrete's durability could reduce environmental impacts through decreased maintenance needs. The comparison remains complex due to differences like steel reinforcements in modern concrete. The findings suggest that using alternative fuels may be more effective for reducing modern cement's carbon footprint than simply adopting ancient practices.

Martinez et al. tested three different Roman concrete recipes with varying slaked lime-to-pozzolan ratios (1:2, 1:3, and 1:4), and assessed greenhouse gas and air emissions for each production stage based on known Roman construction practices. The results surprised the scientists. Per volume of concrete, the production process for Roman concrete ended up emitting as much and, in some cases, more CO2 than modern formulations.

Roman concrete emits much lower volumes of such air pollutants as nitrogen oxide and sulfur oxide—between 11 percent and 98 percent less, depending on whether the energy source was fossil fuels, biomass, or renewable energy. Roman concrete is also more durable and hence would require less maintenance and replacement over time, which might further offset any negative environmental impacts.

'Contrary to our initial expectations, adopting Roman formulations with current technology may not yield substantial reductions in emissions or energy demand,' said Martinez. 'Using biomass and other alternative fuels to fire kilns may prove more effective in decarbonizing modern cement production than implementing Roman concrete formulations.'

'there's a lot of lessons we can draw from'… That statement hints at the potential for learning from ancient practices while developing new, more sustainable construction methods.

Read at Ars Technica