@siin Don't have much direct experience with #biochar, but my friend Michael Whitman of BlueSkyBiochar does.
Biochar needs to be inoculated before you add it to the soil or it will suck nutrients out of the soil and into the char instead of the other way around.
So he says a really effective way to use your char is to add a layer on top of your compost pile whenever it's added to. This has the added benefit of capturing the methane and other gases produced by the composting process. And while the pile is cooking, nutrients are getting established inside the char.
Binder