Hydrochars produced with by-products from the sucroenergetic industry: a study of extractor solutions on nutrient and organic carbon release

Hydrothermal carbonization transforms biomass into value-added material called hydrochar. The release of nutrients (P, N, Ca, Mg, and K) and organic carbon (TOC) from hydrochar in different extractive solutions was investigated in this study. Two sets of hydrochar were produced: (i) hydrochar prepared from sugarcane bagasse and vinasse mixture (BV-HC) and (ii) hydrochar prepared by the addition of H3PO4 to this mixture (BVA-HC). Both hydrochar types released significative amounts of nutrient and organic carbon, mainly Ca (5.0 mg g−1) in the mixture (KCl, K2SO4, NaOH, 1:1:1) extractive solution and TOC (72.6 mg g−1) in the NaOH extractive solution, for BV-HC. Nutrient release was influenced by pH and ionic strength. The release of P, Ca, and Mg was affected by the presence of insoluble phosphate phases in BVA-HC. The release of nutrients P, N, Ca, Mg, and K and organic carbon demonstrated that hydrochar has potential for soil application purposes.