Sustainable Leaching Process of Phosphates from Animal Bones To Alleviate the World Phosphate Crisis

A lack of available phosphorus (P) minerals and their very localized regional distribution threatens world food production. Traditional farming methods that recycle various biological wastes and manure for localized fertilization of farmland are our model but come with risks such as hygiene, water toxification, and passed-on diseases. Here, we present a brand-new hydrothermal process which turns animal bones of kitchen waste into secondary P sources for fertilization, showing that this hydrothermal humification (HTH) process under 200 °C for 24 h completely disintegrates the chemical structure of the biomass, while the simultaneously in-situ-prepared artificial humic acid (A-HA) etches even macroscopic bones. Notably, A-HA can solubilize the insoluble P existing in animal bones partly as directly dissolved phosphorus (DP), accounting for 6.36% of total phosphorus (TP) in the bone wastes. Characterization methods indicate that oxygen-containing functional groups (i.e., −COOH and phenolic–OH) of A-HA can help to corrode bones, causing Ca5(PO4)3(OH) to be decomposed into a large number of more active P minerals, furthermore, leading to a high DP (96.79 mg/L) content and formation of new P-based species. Pot-planting experiments show that the resulting liquids were applied as a fertilizer and led to a significant promotion of the growth of seedlings.