The technology is stunningly simple, working much like a self-cleaning stove : Unsorted garbage is dumped into a chamber; the door is sealed; the temperature is raised to around 380 degrees Celsius and then the contents are turned to vapour and a pile of inert ash. The process, called thermal oxidation, sprung out of rural southern Iowa when the closure of a landfill led two local inventors to collaborate on a cost effective solution to waste disposal. They adapted a machine one of them had been created to generate heat from corn husks and soyabeans. They found that not only could it make garbage disappear, but since it becomes nowhere near as hot as an incinerator, it also left recyclables such as aluminium and glass intact.