Ancient technique helps with modern problem

It looks like our forebears knew a thing or two that we seem to have forgotten in modern times.

" Scientists have revealed that an ancient plowing technique can be successfully employed in the fight against global warming and climate change. Burying charred plants into the soil during plowing season virtually stores them indefinitely, while at the same time provides cultures with an abundant source of fertilizers that can maximize production."

The technique buries biochar into the ground, trapping carbon dioxide in the soil for potentially thousands of years; sort of an ancient form of carbon sequestration.

Full story from SoftPediaNews.

My one question is - how much CO2 is released as stuff is partly burnt to produce the biochar?