If you read up on Terra Preta it is hard not to get excited about the possibilities. Imagine extremely fertile soil that is organic and never needs fertilizer added to it! One main ingredient is Bio-Char...but there is a catch. You need to sort of pre-impregnate the Bio-Char with some Nitrogen for it to really work.
Amazonian Terra Preta Can Transform Poor Soil Into Fertile
You might be able to just mix the Bio-Char with animal manure and get the same effect as long as you let it compost a bit. I didn't really study this particular article but there is a lot of info on the web. The original Terra Preta was suspected to have a lot of human waste in it (not that I'm recommending THAT!) But...human urine is sterile, high in Nitrogen, and practically free.
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Here's a better link:
Terra preta - Wikipedia, the free encyclopedia
Here they stress "liquid" (urine) to "charge" the Bio-Char. It looks like you might need a special South American worm to really get the job done right.