>"Human activities released nearly 37 billion tons of CO2 in 2017. That would yield about 84 billion tons of limestone if it were captured as pure calcium carbo

>"Human activities released nearly 37 billion tons of CO2 in 2017. That would yield about 84 billion tons of limestone if it were captured as pure calcium carbonate." Assuming there is a goal is zero net CO2 added to the atmosphere, that 37 Gt emitted is an upper bound of what needs to be sequestered. Apparently the total amount of construction material used is around 50 Gt per year. https://www.concreteconstruction.net/business/global-demand-for-construction-aggregates-to-exceed-48-billion-metric-tons-in-2015_o https://www.concreteconstruction.net/business/global-demand-... So, that doesn't seem unreasonable to me.