The first commercial coffee roasters were wood fired. There is a certain romantic and artisanal feeling to using such a traditional medium.
The whole operation is very hands on. Wood is chopped. Ash box is emptied. A fire is built with kindling. Control of the roast is achieved by putting in more or less pieces of wood to fuel the fire and by adjusting air flow. Roast profiles rely on sight, smell, sound and a simple bean temperature probe.
Wood fire provides a gentle and moist heat source. This is beneficial to roasting coffee since the heat penetrates the bean allowing for even development and a round flavour profile.