## 4 Discussion
Moreover, the numerous interconnections between the clusters illustrate the interdependence of technical, chemical, and application-related aspects. To illustrate, the extraction conditions (green cluster) influence the quantity and quality of the extracted compounds (purple cluster), which in turn affects their use and product valorization (orange cluster). The co-occurrence of words and keywords analyses demonstrate that the sustainable techniques are predominantly employed for the extraction of antioxidant compounds and bioactive supplements. However, they are also utilized for the production of other products, including biodiesel [36; 37; 38]. One example of the initial green methods employed is the utilization  
of sunflower oil for the extraction of caffeine, which has resulted in the development of a more sustainable technique [39]. One of the earliest investigations into the use of a bio-renewable agrochemical solvent (ethyl lactate) for the extraction of caffeine was conducted in 2013 [40]. Table 2 presents a synthesis of the most relevant information extracted from the analyzed publications. It focuses on the specific coffee products utilized, the techniques and solvents employed, and the obtained products. A variety of factors have been identified as contributors to the waste produced by the coffee industry. The quantity and composition of waste is determined by the specific coffee variety, the growth conditions, and the processing methodologies employed [41]. According to recent estimates, in 2020, global coffee production will exceed 2 billion tons in solid waste [42]. This magnitude represents not only an environmental challenge, but also a reuse opportunity for high-value compounds. \begin{table}
\begin{tabular}{l l l l} \hline \hline \multicolumn{2}{c}{**Utilized Coffee Products**} & \multicolumn{2}{c}{**Extraction Methods**} \\ \hline  & & \(\bullet\) & Ultrasound-assisted extraction \\  & & \(\bullet\) & Microwave-assisted extraction \\  & & \(\bullet\) & Pressurized liquid extraction \\  & & \(\bullet\) & High temperature and pressure \\  & & \(\bullet\) & Green coffee beans & solvent extraction \\  & & \(\bullet\) & Coffee husk & \(\bullet\) \\  & & \(\bullet\) & Cobritical extraction \\  & & \(\bullet\) & Coffee pulp & \(\bullet\) \\  & & \(\bullet\) & Leaves of Coffee & \(\bullet\) \\  & & \(\bullet\) & Coffee silverskin & \(\bullet\) \\  & & \(\bullet\) & Copperchemore extraction \\  & & & \(\bullet\) & Subcritical water extraction \\  & & & \(\bullet\) & Physical and enzymatic processes \\  & & & \(\bullet\) & Chitosan films \\ \hline \multicolumn{2}{c}{**Products Obtained**} & \multicolumn{2}{c}{**Solvents Used**} \\ \hline \hline \multicolumn{2}{c}{\(\succ\)} & Caffe acid & & \\ \multicolumn{2}{c}{\(\succ\)} & Chlorogenic acid and derivatives & & \\ \multicolumn{2}{c}{\(\succ\)} & Caffeine & & \\ \multicolumn{2}{c}{\(\succ\)} & Polyphenolic compounds & & \\ \multicolumn{2}{c}{\(\succ\)} & Flavonoids & & \\ \multicolumn{2}{c}{\(\succ\)} & Catechin and quercetin & & \\ \multicolumn{2}{c}{\(\succ\)} & Phenolic acids (gallic, caffe, ferulic) & & \\ \multicolumn{2}{c}{\(\succ\)} & Antioxidant compounds & & \\ \multicolumn{2}{c}{\(\rightarrow\)} & (melanoidins) & & \\ \multicolumn{2}{c}{\(\succ\)} & Modified polysaccharides & & \\ \multicolumn{2}{c}{\(\succ\)} & Soluble dietary fiber & & \\ \multicolumn{2}{c}{\(\succ\)} & Pectin and cellulose & & \\ \multicolumn{2}{c}{\(\succ\)} & Proteins & & \\ \multicolumn{2}{c}{\(\succ\)} & Trigonelline and theophylline & & \\ \multicolumn{2}{c}{\(\succ\)} & Diterpene esters (cafestol and & & \\ \multicolumn{2}{c}{\(\rightarrow\)} & kahweol) & & \\ \multicolumn{2}{c}{\(\rightarrow\)} & Oils & & \\ \multicolumn{2}{c}{\(\succ\)} & Biodiesel & & \\ \multicolumn{2}{c}{\(\succ\)} & Butanol (produced by fermentation) & & \\ \multicolumn{2}{c}{\(\succ\)} & Edible films & & \\ \hline \hline \end{tabular}
\end{table}