Valorization and Environmental Impacts of Pecan Waste: A Critical Review

Pecan (<i>Carya illinoinensis</i>) cultivation generates a substantial number of byproducts, particularly nutshells, which are often discarded despite being rich in bioactive and structural compounds. These agro-industrial residues, comprising nearly 50% of the total nut mass, contain high levels of phenolics, flavonoids, dietary fiber, and lignocellulosic matter, making them suitable for circular economy applications. This review critically evaluates the potential of pecan shell waste for value-added applications in environmental remediation, food and pharmaceutical formulations, and green materials production. It explores innovative green extraction techniques, such as ultrasound-assisted, microwave-assisted, and subcritical water extraction, to recover valuable compounds like ellagic acid and tannins with high efficiency and minimal environmental impact. Moreover, the review highlights the conversion of pecan shells into activated carbon for wastewater treatment and soil remediation. Pecan byproducts have been used as sustainable feedstocks for catalyst support, contributing to energy conversion and biomass catalysis. The bioactive compounds also offer therapeutic properties, including antioxidant, anti-inflammatory, and antimicrobial effects, supporting their inclusion in nutraceutical and cosmetic applications. Through a comprehensive synthesis of recent studies, this work highlights the role of pecan shell valorization in reducing waste, improving public health, and increasing economic resilience within agro-industrial systems. By aligning with sustainable development and circular economies, the utilization of pecan byproducts provides a low-cost, eco-innovative pathway to mitigate environmental pollution and promote sustainable development.