Hydrochar, digestate, and process water impacts on a soil's microbial community, processes, and metal bioavailability

Hydrothermal carbonization converts organic wastes into potentially soil-improving solids. The nutrient-rich process waters generated are prospective fertilizers. Two hydrochars were produced from maize (Zea mays L.) biogas digestate after 1 or 6 h of carbonization. Nutrient concentrations the digestate, hydrochars, and determined. A 28-d incubation, in which added to a sandy loam soil, assessed their effects on microbial biomass, community composition, respiration, nitrification. became enriched Fe Zn but featured lower macronutrient than feedstock. application as fertilizers could be hindered by electrical conductivity nitrite levels. All amendments stimulated nitrification C mineralization. losses latter add during hydrochar production. Growth biomass was induced particularly due its high bioavailable fractions nutrients. Fungal thrived hydrochar-amended soils, possibly combination aromaticity elevated micronutrient concentrations. separate 56-d incubation tested amendments’ impact metal bioavailability an artificially contaminated substrate. In reducing Cd, Cu, less effective whose likely led increased complexation sorption. However, substrate permitted superior growth; higher surface area porosity may have provided improved habitat. Hydrochar soils benefit hydrothermal is not advantageous where goal sequestration increasing feedstock nutrient availability.