**3.1 Whey protein**

*Waste in Textile and Leather Sectors*

industries [7].

economy.

**2.3 Leather wastes**

than cationic) [10].

for alternative raw material sources [8].

attractive feedstock for chemical, material and biofuel production [7]. Conscious consumption allied with ethical and sustainable values is increasing the consumers' concern in the moment of purchase: "What is the nature of the raw material?"; "What is the life cycle of the product?". This tendency has made the producers look

It was found that the typology of vegetable wastes most produced varies from year to year, with the most abundant being materials unsuitable for consumption or processing, biodegradable wastes and vegetable textile wastes [9]. The most promising vegetable and agroforestry wastes for textile application are, for example, sawdust, coffee grounds, pine bark, eucalyptus bark and others. Sawdust and composites of sawdust (in powder and in pieces) are very abundant wastes as a result of the wood processing industry such as furniture industry. Coffee grounds are highly abundant because the cultural habit of people is drinking a lot of coffee. Pine bark is a highly abundant waste that is very easy to adapt for textile coating applications, which can result in a brown powder that gives rise to coatings with a dark colour and a very attractive shade. Olive stones are also abundant, resulting from the production of olive oil or from the ginning of the olives. Almond or nutshell wastes can create coatings with very attractive colours and visual effects. Rice husk, due to its low nutritional value, is not a viable resource as food for animals, and the burning or landfill deposition of this type of waste has important environmental impacts, as it has a slow biological degradation (high silica content). Eucalyptus bark is also abundant, resulting from the paper and wood processing

The transformation of animal skins into leather allows for the recycling of what would be an organic waste from the food industry into added-value products. In this context, the animal skin is considered a by-product, as it is not reintroduced in the same productive cycle and its reuse contributes to a more sustainable and a circular

There are several applications for leather, and the manufacture of leather upholstery for furniture, airplanes and automobiles has been one of the main markets in the last two decades. Although leather waste recycling has been the subject of hundreds of studies, landfilling remains the most frequent option, wasting all resources contained in leather. Also, due to environmental restrictions, the study and development of sustainable alternatives for the recovery of this waste for the

The valorization of leather wastes such as leather shavings aims to the reduction of the presence and usage of Cr (VI), oil, hydrocarbon, and solvent absorber; adsorbent of chlorides, fats, tannins, surfactants, and dyes, used in the tanning process. Leather powder has already been applied as an oil and crude absorber, while carding powder has been used as an adsorbent for textile dyes (more anionic

This type of waste can be physically processed by crushing and grinding methods. For certain uses, its mixture with resins and catalysts for subsequent pressing between metal moulds with various configurations and sizes can produce multilayer or composite structures. Final products are obtained with a very good appearance, without the need for any additional finishing, with good sound insulation and even good thermal insulation [11]. Applications in furniture, floors and footwear components are some of the examples. Through these processes leather wastes have been used in leather-like materials and construction materials, as additives for thermoplastic composites and as filler materials for reinforcing rubbers [10].

manufacture of new, more sustainable materials are urgent [10].

**108**

Whey exhibits many unique functional properties such as antibacterial and antioxidant activity and odour and water vapour absorber, among others. Therefore, whey has become an attractive product for its versatile applications in different fields, including textile industry. Many of these applications are also reported in the development of new functional products in the food and pharmaceutical fields, due to the properties (such as antimicrobials, antioxidants, and anticancer drugs) and structures of whey protein and its fractions. **Table 2** shows some examples of applying these fractions to obtain the functionalities described.

Another application for whey or milk fractions is related to the production of microcapsules. In fact, globular proteins had been used as a vehicle for the micro-/ nanoencapsulation of bioactive compounds. Milk proteins, namely, whey protein, have been used for the microencapsulation of aromas. Using serum protein isolate and gum arabic, it is possible to encapsulate β-carotene. The same gum arabic had already been shown to be effective in promoting self-aggregation, and consequent capsule formation, of β-lactoglobulin [28–30]. Another aspect is the microencapsulation of β-lactoglobulin with another polysaccharide, chitosan, and this has a


**Table 2.** *Whey, protein fraction and dairy by-product functionalities.* stabilizing effect on serum proteins, protecting them from denaturation at temperatures up to 90°C. Due to its structure, β-lactoglobulin can also form complexes with vitamins and nutraceuticals, such as folic acid. β-Lactoglobulin/folic acid complexes exhibit particle sizes below 10 nm and exhibit stability over a wide range of pH values [31–33].
