Biochar (aka terra preta) is the new darling of organic gardeners.  Everyone's talking about it, and no wonder since terra preta in the Amazon has turned poor ground into high fertility soil that seems to last hundreds of years without any additional input of fertilizer.

What most people don't realize, though, is that biochar is more than just charcoal buried in the ground.  Amazonians probably stumbled upon the mixture accidentally when they combined human waste, crop residue, charcoal from their cooking fires, animal bones, and plain old trash in their midden heaps.  Scientists aren't quite sure why the resulting mixture is so good for plant growth, but until a biochemist tells me otherwise, I'm going to assume that all of the traditional elements are necessary to create true biochar.

Mark and I have decided to experiment with our own biochar composting toilet as a method of adding fertility to our young forest garden.  Our first incarnation is simply a four foot pit dug in the ground.  We'll poop in the hole and intersperse our humanure with leaves, charcoal and ashes from the woodstove, and the poultry bones we need to hide from Lucy.  Presumably, the nearby fruit trees will begin to send their roots into the terra preta as it ages and will get a good meal.  Meanwhile, our system won't require us to handle the humanure at all, unlike most composting toilet systems, so there's absolutely no risk of contamination.  Maybe the biochar composting toilet will replace composting toilets in the near future.