# An Overview on Management and Valorisation of Winery Wastes
## 1 Introduction  
The circular economy presents a compelling argument for how a new economy should use and produce goods. The objective is to achieve \"zero waste\" by maintaining a constant flow of supplies between producers and consumers. Since this system is supposed to have low environmental impact and high economic activity [1], it addresses global issues related to climate change, pollution, waste, and biodiversity [2]. Food waste has negative impacts on the environment and the economy, and its reduction is an urgent necessity. Some methods that can be used to accomplish this goal are represented by dehydration, green extraction, and microwave- or ultrasound-assisted extraction, ensuring food safety and recovering bio-compounds from by-products [3; 4; 5]. The production of wine is one of the industries that must support sustainable development. Given its significance to society and the economy, it is imperative that actions be taken in accordance with the circular economy's assertions regarding the proper use of resources and the restoration of the natural order. Compared with other domains, the wine industry is considered to have a lower environmental influence [6; 7]. Although various studies on sustainability and environmental impact in winemaking technologies have been developed in recent years, one can observe that this was achieved in a disconnected way [6]. This observation served as an impetus for this overview, which aims to highlight whether the application of the circular economy to winemaking technologies will have positive social, economic, and environmental effects. Grapes represents one of the most important fruit crops that are grown on Earth. In 2020/2021 grape production was estimated at about 24.52 million metric tons [8]. Winemaking also produces a high amount of waste (Figure 1), which must be addressed. This waste is rich in biodegradable compounds and suspended solids [9]. Briefly, the resulting residues include plants remains from the de-stemmed grapes, bagasse from pressing, or sediments after clarification. The wastewater resulting from the unification lees has grape pulp, seeds, skins, or dead yeast used in the alcoholic fermentation. In order to increase the overall efficacy and to minimise the environmental impact of the winemaking technologies, various measures have been established, allowing the minimization, management, and efficient recuperation of waste streams in accordance with the circular economy perspective [10]. This approach allows and integrates each element from the production chain and increases the awareness, which is essential to target a real shift towards sustainability, with efficient resource usage and valorisation of by-products and wastes [10]. In this respect, the wine-making industry is urging recycling options to benefit from the wastes through their use as raw materials for value-added products. The most important (in terms of abundance and composition) by-product of the wine-making process is the grape pomace, which constitutes a major source of bioactive compounds, such as dietary fibres, lipids, minerals polyphenols, and proteins [11; 12]. It can be used as a substitute for obtaining various products, as Figure 2 depicts. The by-products resulting from winemaking can be applied for various purposes. Thus, grape pomace and seeds can be used to obtain anthocyanin colourants, oils, or catechin polymers [13]. Moreover, the lees have been used as a supplement in animal feed; however, the yeast content possesses poor nutrient value, and were deemed unsuitable for this purpose [13]. The use of grape pomace is a perfect example of a circular economy. It is estimated that more than 79 million tons of grapes are used annually, with about 30% being represented by grape pomace [14]. It can be used as animal feed and for pharmaceutical purposes, due to its high content of bioactive compounds, mainly phenolics [14], which have antioxidant and anti-inflammatory effects [15].