Characterization and Risk Assessment of Different-Origin Biochars Applied in Agricultural Experiments

This study aimed to assess the impacts of biochar amendments derived from different feedstocks (sewage sludge (SS), olive-mill waste (OMW), compost, and sawdust) in land applications. Tomatoes were used as a test crop in four experiments both under greenhouse and field conditions. SS, OMW, and compost biochar treatments presented 17% to 178.5% higher tomato productivity than control, verifying that biochar behaves as a plant-growth bio-stimulant. This impact is related to the raw material since sawdust biochar did not present results as positive as the other types of biochars. The physicochemical characterization of biochars and their comparison with international and European standards confirmed the safety of their use. A risk-assessment analysis of tomato consumption was conducted in order to explore unfavorable effects on human health. The estimation of cumulative non-carcinogenic risk, found to be between 8.25 × 10−3 and 4.23 × 10−2, and cancer risk for Cr(VI), found to be between 6.56 × 10−6 and 5.2 × 10−5, suggested no risk of potential chronic exposure due to tomato consumption cultivated in biochar-amended soils. This study may be used as a recommendation for farmers and agriculturists for maximizing the yield of agricultural crops in the Mediterranean region, improving soil health, and contributing to the sustainable management of agroecosystems.