Strategic waste management obviates the need to define tradeoffs between agriculture and environmental stewardship by supplying plant-essential nutrients otherwise obtained through industrial processes or mining. Pyrolysis-based sanitation is one such climate-smart option, particularly suited for communities lacking sewerage infrastructure which also suffer from soil fertility constraints. Pyrolysis stabilizes 40% of carbon in human solid waste (HSW) which would otherwise be converted to carbon dioxide or methane in roadside dumps and waterways. In addition, phosphorus (P) and potassium (K) recovery are greater than in animal and green manures, averaging 2.5% (w/w) each. While the high nitrogen (N) content of pyrolyzed HSW, 3.5%, is not immediately plant-available, mineral N in urine, the 'other waste product', can be intercalated into the char matrix by up to 5% (w/w), providing an alternative fertilizer containing 5-2.5-2.5 NPK. This is more than double the concentrations in composted HSW from the same latrines, 1.5-0.8-0.5. Pyrolyzed HSW also had 300-1800% lower lead concentrations than composted HSW, pointing to the fact that quicker sanitization with pyrolysis has advantages in reducing contamination from the ambient environment, which may be exacerbated from long retention time in composting windrows.
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