I am progressively getting convinced that planting tree is NOT a good carbon sink, nor is sequestration in deep well or ocean bottom. Carbon captured in trees is liable to be released back into atmosphere when it is harvested. Deep well and ocean carbon sequestration are subject to earth quarks and untested in sufficient scale.
Do I have a solution? I think I have.
It is biochar. Terra preta has been around for thousands of years and remain stable as carbon. It was estimated that only 2mm thick layer covering all the earth surface with biochar would revert the CO2 back to the pre-industrial level. If all the “excess” carbon dioxide in the atmosphere were converted into carbon and spread across all the earth’s arable lands, there would be 17kg of charcoal per square metre, in a layer 8cm thick. That’s not an unfeasible notion. The Gardening with Biochar FAQ mentions biochar application rates of around 5kg/m2. On the other hand, photos of Terra Preta soils show black layers that are many centimetres thick, so they must contain far more than 17 kg/m2 of carbon. [source]
The task is to develop a business model to make producing biochar and burying into soil economically attractive to investor. Anyone?