Livestock manure-derived hydrochar is more inclined to mitigate soil Global Warming Potential than raw materials based on soil stoichiometry analysis

Hydrothermal carbonization is a green and sustainable efficient technology for treating manure-based wet waste and achieving nutrient recovery. Agricultural application of its products (hydrochar) disrupts the soil's original stoichiometric balance and affects greenhouse gas emissions. However, relationships between soil stoichiometry with methane (CH 4 ) and nitrous oxide (N 2 O) efflux under manure and manure-derived hydrochar application remain unclarified. Pig and cattle manure (PM and CM) and their derived hydrochar (PCs and CCs) were added into agricultural soils to investigate relationships between soil stoichiometry and manure-derived hydrochar input as well as soil CH 4 and N 2 O efflux through incubation experiments. The results showed that PCs and CCs addition increased soil organic carbon and total phosphorus by 8–14% and 12–35%, respectively, compared to PM and CM. Moreover, PCs reduced CH 4 efflux by 58–99%, whereas PCs at low doses (0.5%, w/w) increased N 2 O efflux by 30–202% relative to PM. Manure-derived hydrochar at high doses (1.5%, w/w) reduced global warming potential relative to manure. Furthermore, feedstock and temperature of manure-derived hydrochar were essential factors for soil CH 4 and N 2 O efflux. Our findings contribute to a better understanding of the impacts of manure-derived organic matter-induced changes in soil stoichiometry on greenhouse gas emissions from agricultural sources. Graphical abstract