Sardo, Alma (2025) Valorisation of animal blood for the production of slow-release solid biofertilizers: development of beads and hydrogels, evaluation of agronomic effects and applications in meat-based products. [Tesi di dottorato]

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Abstract

The increasing global demand for food, together with the urgent need to reduce the environmental footprint of intensive agriculture, has intensified the search for sustainable alternatives to conventional chemical fertilizers. Modern agricultural systems depend heavily on synthetic nitrogen inputs, whose production is energy-intensive and contributes to greenhouse gas emissions, soil degradation, and water eutrophication. At the same time, the agri-food industry generates large quantities of organic by-products, such as animal blood, which remain largely underexploited. Within the framework of the circular bioeconomy, the valorisation of such residual biomaterials as nutrient sources for crops represents a promising strategy to close nutrient cycles, minimize waste, and promote soil health. This doctoral research investigates the sustainable valorisation of animal blood, a by-product of the meat industry, for the development of innovative slow and controlled-release biofertilizers. The study focused on the formulation of blood meal (BM)-based fertilizers encapsulated within sodium alginate matrices, either as pure blood-based beads or in combination with the beneficial fungus Trichoderma afroharzianum (strain T22). The agronomic, biochemical, and physiological effects of these formulations were evaluated on four economically and nutritionally relevant crops: lettuce (Lactuca sativa L.), rocket (Diplotaxis tenuifolia L. DC), wheat (Triticum aestivum L.) and Tomato (Solanum lycopersicum L.). Greenhouse and open-field trials demonstrated that BM, particularly when associated with Trichoderma, significantly enhanced plant productivity, nutrient use efficiency (NUE), and soil fertility. In leafy vegetables, BM application notably reduced nitrate accumulation in edible tissues (0.019% vs. 0.793% in controls) and improved nutritional quality by increasing ascorbic acid content (+53%) and total phenolic content. The synergistic BM × Trichoderma interaction stimulated root growth, nutrient availability, and nitrogen assimilation. In wheat, the combined treatment modulated the expression of genes involved in nitrogen metabolism (amt3.1, pdr1, nia7, gs2), confirming a molecular regulatory effect. In tomato BM, with or without T22, significantly affected yield and fruit quality, with the combined treatments generally showing the most favourable responses. Extracts obtained from tomatoes grown under selected BM fertilization were also tested as natural additives in beef burgers. However, they didn’t exhibit antimicrobial activity and their effect on lipid oxidation was modest, with only slight reduction in TBARS during storage, while pH, water activity, and colour remained largely stable. These results suggest that, when included at 1%, tomato extracts provide limited functional benefits but represent a safe and sustainable ingredient for meat products. Future studies could explore higher concentrations, alternative extraction methods, or different plant tissues to enhance their antioxidant or antimicrobial potential. Overall, the results demonstrate that animal blood, when properly processed and biologically enhanced, can serve as an efficient bio-based fertilizer, supporting the transition toward sustainable and circular agricultural systems.

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