# Blyproducts as a Sustainable Source of Cosmetic Ingredients
## 2 Byproducts in Cosmetics
### Animal Byproducts  
The main contributors in this category are the fisheries and meat industries. The former includes fish, crustaceans, and other aquatic animals (but not algae) and is credited with its byproducts accounting for almost 55% to 65% of each year in catch dry weight. Considering that the Food and Agriculture Organization (FAO) estimated that in 2020 over 214 million tons of seafood were produced, one can estimate that roughly 139.1 million tons (65% of total weight) of fisheries byproducts were produced in this year alone [8; 9]. This weight can be mainly attributed to three distinct sources: fish, crustaceans, and molluscs. Heads, intestine, skin, bones, and scales are the byproducts obtained from fish processing, and derived from them are bioactive peptides, collagen, gelatin, fish oil, and calcium phosphates. From crustacean, carapaces and heads are the products generated, and the main compounds obtained are calcium carbonate, chitin, chitosan, protein, and astaxanthin. Lastly, from molluscs, the shell is the byproduct produced and can account for up to 90% of its weight, and proteins, polysaccharides, and calcium are the main compounds obtained [10; 11; 12; 13; 14]. The main applications and products produced with these byproducts can be found in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Source**} & **Sbyproduct** & **Compounds** & **Application** & **Types of Products** & **References** \\  & **Example** & **Extracted** & & & & Face creams, body \\ \hline \multirow{8}{*}{Fish} & Skins, intestines & Collagen and its & Skin elasticity, moisturizing & lotions, shampoos, & \\  & and scales. & peptides, gelatin. & and wound healing. & sunscreens and oral & [15; 16; 17; 18] \\  & & & & & supplement. & \\ \cline{2-6}  & Fish off-cuts (skin & & Skin reaction to UV, acne & & \\  & with stuck & Oil rich in PUFA. & decrease, MMP-1 & Oral supplement. & [19; 20; 21] \\  & muscle). & & production inhibition. & & \\ \cline{2-6}  & Fish bones. & Natural calcium & & & \\  & phosphates. & UV protection. & & & \\ \hline \multirow{4}{*}{Crustaceans} & \multirow{4}{*}{Carapaces.} & \multirow{4}{*}{Chitin and chitosan.} & Delivery systems of active & & \\  & & & compounds, structural & Sunscreens, cosmetic & \\ \cline{1-1}  & & & component and & mask, shampoo. & [24; 25; 26] \\ \cline{1-1}  & & & antimicrobial. & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Fish byproducts’ main cosmetic-related applications. PUFA: polyunsaturated fatty acids; MMP-1: matrix metalloproteinase-1. When considering examples of the applications given in Table 1, one question stands out. How are the referenced materials attained? In the literature, various examples can be found for the different categories considered. For fish byproducts, one can consider the work of [PERSON], [PERSON] [31] in which, through a combination of acid and alkaline treatments with an autoclave (pression and temperature)-based extraction, collagen hydrolysates were attained from Romanian carp skin. When talking about crustaceans, a clear example is the chitin and chitosan extraction procedure from these animals' byproducts (namely, shells) through alkaline extraction with NaOH, a process which is normally milder (less temperature, NaOH, or time) than the traditional extraction from animals [32]. For molluscs, traditionally, their shells are thermally treated (up to 500 \({}^{\circ}\)C) and then milled to remove their mineral fraction or subjected to proteolytic hydrolysis prior to thermal treatment to extract the protein content of mollusc shells [33]. Another topic that has to be considered when talking about fisheries byproducts is their intrinsic advantages compared to meat-industry-derived ones. First, fish-derived collagen and its peptides have a more varied composition and higher stability than its mammalian counterpart. Secondly, there is a lack of zoonotic diseases such as transmissible spongiform encephalopathy and foot and mouth disease that can affect bovine and porcine collagen.