A system and method uses a combustor and gasifier to burn a primary dirty fuel, such as waste materials or high-polluting fossil fuels, and a secondary low-polluting fuel, such as biomass fuels, for co-generation of electricity while reducing harmful emissions. The primary fuel is burned at least partially through the use of an improved burner tube. Dirty exhaust from a combustor is scrubbed by a gasifier by reforming the combustors exhaust gases into a clean-burning producer gas (syn-gas). The secondary fuel and oxygen are added to the dirty exhaust in the gasifier to create gas, char and ash. The gas powers an engine or turbine that turns a generator, or a boiler, Stirling engine, or Organic Rankine Cycle power plant, and releases a cleaner exhaust.