The ancient Amazonian Indians knew how to do it! https://news.nationalgeographic.com/news/2008/11/081119-lost-cities-amazon.html
Well, I was just thinking of the new book out called, "1491" and how it goes into how the Americas were a giant food forest already that was destroyed... ..this kind of goes hand in hand with that book.
Apparently the terra preta soils took hundreds of years to create and do not just contain charcoal, but bones, pottery, and other debris, piled up or buried for generations. In other words, biochar is not the same as terra preta and the two should probably not be conflated. One of many articles on the website: https://permaculture.org.au/2010/11/21/biochar-potential-or-pitfall-carbon-storage-vs-soil-quality/
Permaculture: a path toward a more sustainable Amazon? Was going to post this as a separate news item but it seems to belong here Permaculture: a path toward a more sustainable Amazon? https://news.mongabay.com/2012/0503-park-interview-eco-ola.html