Hi gb

Venus would've lost next to zero CO2 - it's just too heavy. There's no way Earth ever outgassed 10,000 bar of CO2 in the last 2 billion years. The mass alone is the equivalent of ~40 kilometres of crustal rock over the whole surface. Falkowski's original quote is talking about biomass sequestration. There's only ~ 10 trillion tons of carbon in the biosphere. There haven't been that many (1.5 million) total burials of the biosphere in 2 billion years and only 25 billion tons of sediment hit the oceans in a year, not just sequestered organic carbon. I suspect the real figure is 15E+18 kilograms. The estimated mass of buried carbon as coal is just ~ 10-20 E+12 tons, for comparison.