Biochar is interesting. It seems to be dependent on the temperature your pyrolysis occurs at and likely many other variables. It also encourages microbial growt

Biochar is interesting. It seems to be dependent on the temperature your pyrolysis occurs at and likely many other variables. It also encourages microbial growth that can help sustain and even add to the carbon content. There are studies that show it can sequester carbon from dozens to hundreds of years potentially, and patches of "terra preta" found in the Amazon are found to be self regenerating (growing at 1cm/yr) and were originally set down between 450-950BCE. Fascinating stuff.