A very detailed article on biochar and its effects on soil: https://onlinelibrary.wiley.com/doi/full/10.1111/gcbb.12885
Biochar is fairly simple to make at home, using things that would otherwise go to waste. Including “waste”. The charring process kills off any nasties that might be in the material, so it’s also a good way to deal with diseased or infested materials.
Will check it out. Supposed to be great for tropical soils but not so great for heavy soils in temperate climates which is me. I did see where in a study, they used it as a replacement for perlite in a potting mix because it has similar moisture absorption/retention capabilities. Also, part of my property has pale, fast draining soil so biochar might be good for that.