Valorization of agri-food wastes: impacts of vinasse, olive pomace, and tomato peel biochars on plant physiology, soil health and sustainability

Introduction: Utilizing agri-food by-products and residues to create soil improvers reduces waste and promotes environmentally friendly agriculture within a sustainability framework. This study evaluates the agronomic, biological, and economic impacts of biochars produced from three agri-food residues: vinasses, olive pomace, and tomato peels. Methods: Biochars were applied to tomato (Solanum lycopersicum cv Heinz 1301) and wheat (Triticum durum cv Svevo) in a greenhouse experiment at concentrations of 0.1-0.25-0.5% w/w, to assess their effects on plant biomass, physiology and gene expression, total countable microorganisms, enzymes involved in nitrogen mineralization (arylamidase), cellulose degradation (β-glucosidase) and phosphorus release (phosphatases). Economic and environmental assessments were also carried out. Results and discussion: Vinasse biochar contained the highest levels of nitrogen (12000 mg/kg), potassium (11700 mg/kg), and phosphorus (4200 mg/kg), performing comparably to vinasse-based compost. A concentration of 0.5% biochar derived from vinasses increased canopy cover in tomato (+125%), and stem length (+13%), fresh and dry root weight (+97% and 57%, respectively), and stem weight (+41% and 44%, respectively) in wheat. The same biochar modulated genes involved in plant growth and development, cell wall biogenesis, nutrient transport, hormone signaling, and stress response in both plants. All biochars, particularly those derived from vinasses, enhanced arylamidase activity in tomato plants compared with the control. The same biochar enhanced activity of β-glucosidase when added at 0.5% in wheat (+ 29%) and tomato (+20%) over the control. Biochar derived from tomato peels at 0.5% enhanced the phosphatase activity (+27%) in tomato plants, while biochar derived from olive at 0.5% enhanced the same activity (+45%) in wheat. Economic and environmental evaluations revealed that these biochars were better than composts derived from the same residues, in terms of sustainability and economic value.