Assessing the Impact of Sustainable Biochar-Enriched Substrates on Safety and Quality of Tomato (Solanum lycopersicum L.) as Relevant Model Crop

Forestry-waste biochar was tested as a commercial substrate (peat:lapillus 1:1 v/v) amendment in growing tomatoes (Solanum lycopersicum L.). Substrates were 0% (control), 5%, 10%, 20%, and 40% (% v/v) biochar-enriched and were characterized for their textural and physicochemical properties. After harvesting, tomato production (i.e., plant and fruits), quality (e.g., nutrition and nutraceutics), and safety (i.e., biochar-related pollutants) were assessed according to the different growing media. 10-to-40% biochar-enriched substrates only exceeded the pH threshold set by L.D. 75/2010. Ni and Mn exhibited a similar trend between substrates and fruits, while Cr, Pb, and Cd were absent. Plant biomass increased (up to 11–29%) according to biochar content, which conversely diminished fruit production (∼25–60% reduction). Only acenaphthene exhibited an increasing profile (11–12 μg kg–1) according to the treatments, nevertheless complying with the European regulations. PLS-DA confirmed practice suitability by substrate–crop correlation, providing prediction models for quality and safety assessment.