The issue with pizza ovens specifically is that they reach operating temperatures (450-500C / 840-930F) where black carbon does not accumulate, it oxidises away into the air. I see this happen every time I use my pizza oven and leave some flour behind in it.
Yeah I was going off at a tangent from pizza ovens.
Pyrolysis happens when you heat wood in a chamber with low ventilation (low oxygen) , which causes flammable gases (methane, CO etc) to be emitted, leaving black carbon. The flammable gases are then burned separately, to sustain the process and also to heat whatever you want. Methane burns at hot enough temperatures to power a pizza oven; so in theory you could construct one powered by pyrolysis, but it isn't going to happen in an unmodified one. A normal one should be constructed to ventilate the wood well, to avoid emitting too much CO.
There is a video on youtube of some guy pyrolizing some wood by putting a metal box with it in in his oven - it's not rocket science. But I live in a city, so in the end it didn't seem like a good idea to experiment with it.
