The best environmental option for residual waste is to phase it out, as prevention, reuse and recycling are all more environmentally beneficial than residual waste treatment; but is there a preferred treatment method for residual waste in environmental terms? As levels of recycling municipal solid waste increase, there will be a greater need to differentiate between the fate of different materials. Residual waste after recyclables are removed is likely to contain considerable quantities of green waste. The preferred method for treating this part of the waste stream might be anaerobic digestion which produces both energy from waste and a soil improver if it is used to treat source separated biodegradable waste. Residual waste will contains materials which are either non-recylable through their not having been separated out early on, or materials for which their is no commercial market, including some plastics and metals. Residual waste will also contain a proportion of inert waste materials, for which neither MBT/RDF or direct incineration has much to offer as a disposal route for such materials; and a proportion which will eventually require landfill.