Isolation of Thermally Stable Cellulose Nanocrystals from Spent Coffee Grounds via Phosphoric Acid Hydrolysis

As the world's population exponentially grows, so does the need for the production of food, with cereal production growing annually from an estimated 1.0 billion to 2.5 billion tons within the last few decades. This rapid growth in food production results in an ever increasing amount of agricultural wastes, of which already occupies nearly 50% of the total landfill area. For example, is the billions of dry tons of cellulose-containing spent coffee grounds disposed in landfills annually. This paper seeks to provide a method for isolating cellulose nanocrystals (CNCs) from spent coffee grounds, in order to recycle and utilize the cellulosic waste material which would otherwise have no applications. CNCs have already been shown to have vast applications in the polymer engineering field, mainly utilized for their high strength to weight ratio for reinforcement of polymer-based nanocomposites. A successful method of purifying and hydrolyzing the spent coffee grounds in order to isolate usable CNCs was established. The CNCs were then characterized using current techniques to determine important chemical and physical properties. A few crucial properties determined were aspect ratio of 12 +/- 3, crystallinity of 74.2%, surface charge density of (48.4 +/- 6.2) mM/kg cellulose, and the ability to successfully reinforce a polymer based nanocomposite. These characteristics compare well to other literature data and common commercial sources of CNCs.