Health risk mitigation and fruit flavor enhancement: A dual strategy for safe agricultural application of municipal sludge-derived nutrient stimulants

Advancing municipal sludge toward high-value utilization has emerged as an urgent priority for sustainable waste management. This study investigated the efficacy of sludge-derived nutrient stimulants (SNS), produced via alkaline thermal hydrolysis of municipal sludge, as a sustainable agricultural amendment that concurrently addresses waste recycling and fruit quality. SNS application markedly enhanced flavor attributes and nutritional profiles, alleviating bitterness and astringency through promoting the conversion of alcohols and aldehydes into aromatic esters. Meanwhile, it was revealed that SNS application reduced synthetic pesticide reliance, slashing residual pesticide levels by eight-fold and ensuring all measured health risks remained below safety thresholds. Metabolomic analysis indicated that SNS application activated the tricarboxylic acid (TCA) cycle, anthocyanin biosynthesis and Ascorbate-Glutathione (AsA-GSH) cycle, thereby improving carbon-nitrogen metabolism, fruit coloration, antioxidant capacity and potential health benefits. Our findings position SNS not merely as a bio-stimulant, but as a multifaceted tool for circular economy agriculture. It offers an integrated strategy for sludge management, pesticide mitigation and reduced environmental footprint, paving the way for circular agriculture and sustainable environmental management.