## 6 Agro-Industrial Food Waste for Nanocellulose Production  
### Agricultural Waste in Circular Economy  
In the 21 st century, population growth has raised the need for food and energy, which has resulted in a rapid depletion of natural resources over time. This increase in population and demand for resources has put pressure on the food processing industries, which produce large amounts of plant, animal and agricultural residue wastes, thereby accumulating a huge amount of waste throughout the year due to a lack of effective waste management methods [10]. The majority of food waste is produced during its production, harvesting, transportation, industrial processing and consumption [22]. According to estimates, one-third of all food produced worldwide is wasted or lost, with the fruit, vegetable and seafood industries playing a significant role in this. An estimated 1.3-2.0 \(\times\) 10\({}^{9}\) tons of waste (between 33% and 50% of the world's food production) is produced by the food industry annually, with fruit, vegetables and their by-products contributing to the largest amount of approximately 0.5 \(\times\) 10\({}^{9}\) tons per year. Around 100 Mt of food waste and by-products are produced annually solely in Europe, with the fruit and vegetable industry accounting for 14.8% of this total [22; 133; 134]. Moreover, residues from the agriculture industry (agro-industrial waste), which is also one of the types of LB, plays a significant role in waste generation. A total of 998 million tons of agricultural residues of all kinds are produced per year throughout the world, which includes rice/wheat straw, corn stover and a number of other economic crop leftovers [135]. This waste does not only exacerbate the food deficit, but also harms the environment when improperly disposed of, contaminating the land and water sources. Due to a number of obstacles, including the product's stability, pathogenicity, auto-oxidation potential, high water content and strong enzymatic activity, disposal of this waste incineration and landfilling is perilous. Waste products from the agriculture and food industries often contain useful substances that can be recovered and used to produce environmentally benign and viable products.  
The concept of \"circular economy\", which advocates using organic waste from one industry as a source of raw materials for another for the production of value-added products, has gained significant interest in recent years. It is based on the implementation of the 5 Rs principles of sustainable development, which are reduce, reuse, recycle, recovery and restore. These principles overcome the traditional practice of \"take, make, use and throw\" [4; 22]. Therefore, following the practice of \"circular economy\", the agro-industrial waste, being rich in carbohydrates, proteins, lipids, organic acids and other necessary minerals, can be directed toward the production of sustainable products for its value addition. The exploitation of residual agricultural processing wastes is still in its infancy and is primarily defined by low value-added applications, such as direct combustion for heat production or use as a fertilizer/compost. Nevertheless, from economic aspects or environmental advantages outlook, these uses have not yet fully realized their potentials. Moreover, apart from the renowned potential of agricultural waste in producing biofuels, it can also be used to produce NC that possess promising applications in cosmetics, drugs, biomedicine and many other industries [18; 136].