## 1 Introduction  
The avocado (_Persea americana_ Mill.) is a tree native to Mesoamerica, whose origin is in the central part of Mexico and some parts of northern Guatema. The name of the avocado comes from Nahuatl (Ahuacatl), a word that means \"tree testicles\" [1]. Avocado belongs to the family Lauraceae [2]. The Lauraceae family is one of the oldest among the flowering plants; particularly, avocado is the most important and only edible fruit of this family and has a high commercial value [3, 4, 5]. Production areas were concentrated in Central and South America, but it is currently cultivated worldwide. Avocado consumption is growing everywhere, and it has caused a large number of countries to invest heavily in avocado production (Figure 1a). Based on the average production between 1998 and 2018, the top 10 avocado producing countries were firstly Mexico, followed by the Dominican Republic, Indonesia, Colombia, United States, Peru, Brazil, Chile, Kenya, and China [6]. Figure 1b shows the production of avocados in these top 10 countries in 1998, 2008, and 2018. It highlights that Mexico is the major producer and the production was generally increased not only in this country but also in all these countries. In 2018, the world's avocado production was around 6.4 million tons, of which these countries produced 77.4% [6].  
Avocado has a dark green, rough find that covers a yellow-green pulp rich in oil [7]. Avocado has a unique texture, a smooth, buttery consistency, and an exquisite taste and aroma compared to most fruits, which present a typically sweet or acidic taste [8]. In addition to its pleasant organoleptic characteristics, avocado consumption has caught consumers' attention owing to its high nutritional value and reported health-benefits, the main driver for buying avocados [9]. An avocado fruit consists of the peel (7-15%), pulp (65-73%), and stone (including the seed) (14-24%) (Figure 2) [10; 11; 12]. The pulp  
Figure 1: Production quantities of avocados by country in 2018 (created with mapchart.net) (**a**) and by the top 10 producers in 1998, 2008, and 2018 (**b**). Based on FAOSTAT data [6].  
of the avocado is consumed fresh or in the form of halves and frozen cubes. Other processed products are also obtained from avocado, such as guacamole, oil, jams, candy juice, ice cream, or as a sauce like dips, chutney, sandwich spreads, mayonnaise, etc. In addition, research has been done on the conservation of avocado fruit by dehydration, freezing, and canning [14; 15].  
The consumption and the industrialization of avocado gives as a result a huge amount of waste, not only the peel and stone but also the waste generated by the pruning practices and oil extraction. As Figure 1b highlights, avocado production has a tendency to grow and thus this waste is going to generate more environmental pressure. However, these biomasses could be converted into raw materials to obtain different types of co-products, but this implies several changes in the use of these resources, the design of efficient production systems, and integration to take full advantage of them. In particular, the integration of several valorization ways to produce a portfolio of products, such as energy, fuels, and/or bio-based products--in a single installation--is attractive; i.e., a biorefinery [16; 17; 18]. Therefore, this review firstly gives a snapshot of those residues generated by the avocado industry. Then, it presents updated information about the valorization ways reported to obtain marketable products from avocado waste in a single process or integrated processes within a biorefinery context. In the framework of a circular bioeconomy, it can be the basis for improving the regional economy, generating jobs in the localities where avocado is grown and processed and promoting economic growth by extending the value chain.