Sustainable strategy for the agri-food chain: examples towards a circular economy

Over the past decades, the agricultural sector has undergone a profound transformation driven by rising global food demand, rapid technological innovation, and the urgent need to mitigate the environmental impacts of conventional production systems. This doctoral thesis contributes to the scientific debate on the transition toward a circular, bio-based, and sustainable agricultural model by addressing three interrelated research domains: the valorization of organic fertilizers, the upcycling of agro-industrial by-products, and the functional role of beneficial microorganisms within the rhizosphere. The first research line investigated the conversion of poultry manure through the AFRODITE® aerobic fermentation process, which produces stable and nutrient-rich organic fertilizers. This approach supports soil fertility enhances microbial biodiversity, and reduces greenhouse gas emissions, in accordance with the European Fertilizing Products Regulation (EU 2019/1009). In parallel, the thesis explored the valorization of agro-industrial residues such as coffee silver skin, orange peels, and artichoke by-products for the development of biodegradable and functional biocomposite materials designed for agricultural and packaging applications. These bio-based materials, enriched with bioactive compounds, exemplify the principles of the circular economy by closing carbon and nutrient cycles while reducing dependence on fossil-derived plastics. Finally, studies on plant growth-promoting rhizobacteria (PGPR) demonstrated their capacity to enhance crop yield, nutrient use efficiency, and nutraceutical quality, emphasizing the pivotal role of the rhizosphere microbiome and its synergistic interactions with organic amendments. Overall, the results presented integrate biotechnology, microbiology, and materials science in order to promote the regeneration of agri-food systems, increase soil health, and improve agricultural production.