Coffee beans are traditionally roasted by utilizing electricity, whose production may or may not be clean. Introducing PuroSole, a company whose solar method of roasting coffee beans is eco-friendly.
Its system uses sunlight reflected from self powered autonomous mirrors to directly roast coffee beans. This working principle is very similar to a solar furnace or heliostat, as using solar mirrors is cheaper and requires less resources.
There’s much more to this efficiency, of which is explained in much detail (and I mean lots) on their website. Apparently, coffee roasting is a very sophisticated science and process. One of the interesting facts in coffee roasting is that after the coffee beans reach a specific internal temperature, it starts to self-combust, heating itself!