The invention includes a downdraft gasifier having a rotatable auger/grate extending through its reduction zone. The auger at times moves biofuel through the gasifier and at times supports it in the gasifier. A frusto-conical biomass grate funnels biomass onto the auger and is perforate for permitting the passage of gases while retaining the biomass. A guide tube surrounds the auger below the frusto-conical biomass grate. The invention also includes mixing gas or solid particulate fuel in a conduit segment that houses a mixing chamber. Fuel is fed through a fuel inlet port into the mixing chamber. High velocity combustion air from a blower is forced into the mixing chamber through a restricted orifice that generates a suction pressure for drawing gas or solid particulate fuel into the mixing chamber. A combustion chamber supply conduit delivers fuel from the mixing chamber into a burner.