Apple pomace represents an important agro-industrial residue with high moisture content and significant environmental burden if improperly managed. This study investigated its thermochemical valorisation into biochar via two processes, followed by comprehensive physicochemical characterization and agronomic evaluation. Elemental analysis revealed carbon enrichment from 47.89% in raw material to 77–78% after the thermal process, evidencing a progressive aromatization. Scanning electron microscopy, Fourier transform infrared spectroscopy, and Raman analysis confirmed a temperature-dependent transition from partially amorphous carbon (400 °C) to more ordered aromatic structures (450 °C), while excessive thermal treatment (550 °C) increased structural defects. ICP-OES revealed an enrichment in thermally stable metals (Fe, Al, Mn) and limited Cd accumulation. Germination assays using Triticum aestivum L. demonstrated that biochar produced at 400 °C significantly improved the germination uniformity and seedling height (14.1 mm), as well as biomass accumulation compared to the control soil sample. The fertilizer addition increased the soluble Na and electrical conductivity (up to 643 µS/cm), potentially inducing transient salinity stress. Soil chemical analysis indicated increased K availability in soils amended with biochar produced at 400 °C, whereas the combination of biochar obtained at 450 °C with fertilizer conducted to elevated concentrations of certain trace metals, mainly Ni and Cr, highlighting the demand for careful monitoring. Overall, the biochar produced at 400 °C yielded to an optimal balance between structural stability, nutrient enrichment, and agronomic performance, evidencing that apple pomace may be a viable feedstock for sustainable biochar production within circular bioeconomy frameworks.

The management of agri-food waste is a major environmental and economic challenge. Potato peels are a significant by-product of the food industry. They are rich in dietary fiber, phenolic compounds, residual starch, vitamins, and minerals. Valorization of potato peels into value-added products is a promising solution. Biochar and bio-oil can be produced via pyrolysis and hydrothermal carbonization. Hydrothermal carbonization converts wet biomass into hydrochar under moderate temperature and pressure, while pyrolysis decomposes peels in the absence of oxygen into solids, liquids, and gases. Potato peel biochar enhances soil fertility, sequesters carbon, adsorbs pollutants, and reduces greenhouse gas emissions. Chemical analyses confirm high nutrient and phenolic content with trace heavy metals, ensuring safety and efficiency. Overall, these treatments transform potato peel waste into renewable resources, supporting circular economy practices and climate change mitigation.