Pyrolysis is the heating of organic material in the absence of oxygen. It is used in the chemical industry to produce ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood, or to produce coke from coal. It is also used in converting municipal solid waste into its basic carbon components.
It has been proposed as a way of eliminating heavy metals and toxic industrial compounds from sewage sludge and converting them into raw materials, carbon, and fuel. However, those early proposals are based on the flush toilet-canalization-sewer-wastewater treatment plant paradigm. This means that we would not be changing our habits of flush and forget.
However, there are more recent studies that show the viability of pyrolysis of human excreta from dry toilets, as this research paper demonstrates.
As this study comments, several industrial waste plants successfully use or have used pyrolysis but there is still a big challenge to make pyrolysis economically viable, thus the next studies should focus on the implementation of the latest developments in pilots and on an industrial scale.
Pyrolysis will become an important process in recycling the NPK and other micronutrients from human excreta from dry toilets.