Efficient anaerobic digestate valorization: Nutrient recovery strategy for enhancing soil fertility in arid agricultural regions

Efficient nutrient cycling in agroecosystems is essential for sustainable agriculture, and the utilization of waste products from various industries can contribute to this process. In this study, we investigated the potential of using anaerobic digestate from food industry waste (sugar beets and food waste) as a nutrient source for fertilizer production. Digestates were sanitized using a mixture of inorganic acids (H2SO4 and H3PO4) or alkaline (KOH), with acidic hydrolysate yielding a higher concentration of amino acids (1981 mg/L) compared to alkaline (186 mg/L). The acidic hydrolysate was centrifuged, and the liquid fraction was used to create a foliar fertilizer. The solid fraction, acidic hydrolysate, sewage sludge incineration ash, and additives (ammonium nitrate, urea with urease inhibitor) were employed to formulate three granular fertilizers. Nitrogen balances were analyzed using Sankey charts for each fertilizer formulation. The highest nitrogen losses (45.90 kg N/1 kg formulation) were recorded in the production of fertilizer containing ammonium nitrate. The fertilizers' effectiveness was evaluated through preliminary wheat germination tests. The highest yields observed for the foliar fertilizer (1% dose) and granular with the addition of urea with a urease inhibitor (20% dose) groups, where fresh sprout mass was approximately 18% and 23% higher than the control, respectively. These findings demonstrate the potential of using anaerobic digestate from food industry waste for nutrient recycling in agroecosystems, contributing to sustainable agriculture.