In using the pyrolysis and gasification reactor and microwave plasma torch 100, 200 to pyrolyze a supply of waste, a volume of the supply of waste is loaded into the reactor chamber 520 of the reactor unit housing 510. The microwave plasma troch 100, 200 is then powered to apply a stream of plasma to the supply of waste at a suitable temperature. In some embodiments, the specific value of this suitable temperature may be determined based at least in part on the contents of the supply of waste. The application of the stream of plasma from the microwave plasma torch 100, 200 produces a volume of at least one useful product gas, where the at least one useful product gas can be extracted from the reactor chamber 520 via the gas outlet conduit 540 for further processing and/or purification.