Waste to Wealth: Sustainable Valorization of Walnut Shells into High-Value Bio-Based Materials

Abstract

Sustainable management of agricultural wastes has gained more and more attention in the world particularly in the production of value added products that are renewable and rich in carbon. Moreover there is the necessity to offer low cost and lower energy alternatives to active carbon and removal of contaminants in water. The walnut shell is an organic abrasive of hard nature and is environmentally and cost effective. Ash made of walnut shells, which is rich in alkali and alkaline earth elements has potential as a catalyst in transesterification reaction. Besides walnut shells can be converted to biochar through pyrolysis and this product is a low cost adsorbent that is useful in the removal of arsenic. Iron loaded biochar (ILB) which is a product of waste walnut shells has a significant arsenic adsorption capacity. Being a renewable resource, the walnut shell biomass has a broad spectrum of applications in bio based products such as biofuels bioenergy biochemicals and biomaterials. A review will be done on the different thermochemical conversion processes with emphasis on liquefaction of wood and how biomass composition affects the liquefaction process and chemical properties of the weakening biomass liquefied product. Walnut shells (WS) are a good example of hazardous material removal bio sorbents owing to their extraordinary absorbency and bio sorbent properties. WS powder has also antioxidant compounds as well as useful substances such as charcoal and pyroligneous acids. In addition to bio sorbent walnut shell is also handy in reinforcement filler to thermoplastic composites especially in outdoor applications where the component has to be very dimensional stable. Their versatility and potential are evidenced by its use in various industries, which show the flexibility and innovativeness of the walnut shell.