Exploring the Potential and Obstacles of Agro-Industrial Waste-Based Fertilizers

Conducted in Southern Italy’s Calabria region, this study aimed to repurpose olive wastes, which are still a source of valuable biomolecules including plant nutrients, flavonoids, polysaccharides, and phenolic compounds, into compost to be used in sustainable agriculture as fertilizers, in alternative to synthetic substances. The compost underwent chemical analysis and soil fertility testing to support eco-friendly agricultural practices. Factors like extraction process, waste composition, and percentage of waste in composting were studied for their impact. The research evaluated compost fertilizing effectiveness by analyzing soil chemical and biological properties 180 days after the application. The results demonstrated that the proportion of olive oil waste and the olive oil extraction method significantly impacted compost quality and its environmental footprint. All composts improved soil properties but to a different extent. Compost olive waste 3 (OWC3; 34% olive oil waste, 33% buffalo manure, and 33% straw) was the most effective in enhancing soil fertility. Compost olive waste 1 (OWC1), with the same olive waste percentage as compost olive waste 2 (OWC2) but from a different extraction process, outperformed OWC2 in enhancing soil fertility and microbial activity. The research highlighted the importance of organic matter addition to soil and the significant role of both raw material percentage and extraction process in compost quality. Life cycle assessment indicated that OWC3 had the lowest environmental impact and the highest fertilizing power. Composting represents a practical way to manage organic wastes and improve soil quality, providing essential nutrients for soil health and ecosystem functioning.