The UN has a target of raising the organic Carbon content of soils by 4 parts per thousand in order to offset atmospheric Carbon dioxide growth and global warming.
In a short report in “The Auger” (one of the journals of the British Society of Soil Science) the work of Johnson A E, et al. in The European Journal of Soil Science concluding that, using crop production with mineral fertilisers and Nitrogen from legumes, such a target probably could not be achieved.
They have much greater knowledge than I and my limited knowledge would concur with that view. However, fertilising crops based on composting urban wastes could easily achieve, and surpass that target. It has been done. See https://www.amazon.co.uk/Reversing-Global-Warming-Profit-environmentally/dp/1904312810
Bill Butterworth, Land Research Ltd