Benefits and Limitations of Using Hydrochars from Organic Residues as Replacement for Peat on Growing Media

New technologies for the production of peat-substitutes are required to meet rising demand growing media in horticulture and need preserve natural peatlands. Hydrothermal conversion organic residues into char materials, hydrochars, with peat-like properties may produce such substitutes, reducing environmental impacts CO2 emissions from improper management. To assess their potential as a component media, cress seed germination tests used hydrochars digestate (D), spent coffee grounds (SCG), grape marc (GM). Pre- post-treatments (extraction, washing, drying) applied remove phytotoxic compounds associated process waters retained on nitrification bioassay water is predict toxicity. All achieve similar or better results compared feedstock, showing replace at least 5% peat media. SCG GM show inhibition above 5%, while all post-treated D-hydrochar mixtures >3 times longer roots than control. The test shows high sensitivity good agreement trends found water. Such can be way optimize combinations hydrothermal replacements.