I made a batch of biochar that looks similar to that, but not quite as done last year. I left it in a plastic barrel that filled up with water over the winter. Mind you, this was pure charcoal. No inoculation, no ammonia, no seeds, no dirt, nothing added.

I was questioning whether or not it was going to be good as well. So I'm not suggesting it is optimal, but I saw a few seedlings growing in it under about 2 inches of water and they looked quite happy. I'm not saying it is optimal, but I'm confident it's going to be just fine.