# Bio-Sourced and Biodegradable Membranes
## 4 Green Membrane Technology Applications
### Fuel Cell  
Fuel cells (FC) are a sustainable energy source with high efficiency that converts the chemical energy of the organic matters (fuels) into electricity and can replace fossil fuels [247]. This technology has a low environmental impact and can be employed in various devices to reduce global pollutions [2]. A fuel cell consists of an anodic and cathodic chamber as well as an electrolyte that separates the two chambers and facilitates the transfer of ions. In FC, membranes can be used as electrolytes, known as proton exchange membranes [248; 249]. The most common membrane used in FC is Nafion, which has a high production cost and environmental impact [250]. Therefore, using the biodegradable membranes could be a promising alternative to Nafion. [PERSON] et al. [251] prepared biodegradable membranes using PVA, CS, and their compositions, and they compared their performance in a microbial fuel cell (MFC) to Nafion commercial membrane. According to their findings, PVA/CS membranes had a lower O\({}_{2}\) permeability compared to Nafion, resulting in maintaining the anaerobic condition in MFC. They also reported that the PVA/CS composite membrane led to higher power production and lower cost, as well as less environmental impact. Aside from their high cost and environmental impact, Nafion membranes have shown a high fuel crossover (methanol or hydrogen leakage) and low ion conductivity in electrolyte membrane FC. Chitosan and alginate-based bio-membranes are strong candidates to tackle this issue [30; 250; 252; 253]. [PERSON] et al. [254] prepared a chitosan/sodium alginate composite membrane and used that for the methanol fuel cell. The composite membrane exhibited an excellent mechanical property with low methanol permeability (4.4 \(\times\) 10\({}^{-8}\) cm\({}^{2}\)/s for CS/SA and 27.6 \(\times\) 10\({}^{-8}\) cm\({}^{2}\)/s for Nafion117) and favorable proton conductivity. In addition, they noted that the membrane was fabricated using a simple and cost-effective technique. In another study [253], they prepared PVA/CA and PVA/CS composite membranes and evaluated their performance in methanol fuel cell. Similar to previous research, the composite membranes demonstrated lower methanol permeabilities in comparison with Nafion117. More researches on using biodegradable membranes in proton exchange membrane fuel cells are presented in Table 2. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Polymer** & **Application** & **Advantage** & **Disadvantage** & **Ref** \\ \hline PLA/PBS/SNPs & Oil/water & Favourable thermal stability, high & Low metal ion and & \\ PLA/PPC/SNPs & separation & separation efficiency and turbidity & dissolved solid removal & [1] \\ PLA/PHB/SNPs & & removal (-98\% and \(>\)89\%, respectively) & & \\ \hline CS & Oil/water & Excellent underwater superoleophobicity, & Low diesel removal in & \\ separation & stable wettability in various pH, \(>\)99\% oil & & saline solutions & [113] \\ \hline CAF/CS/CF & Oil/water & Superhydrophilicity and underwater & & \\  & separation & superoleophobicity property, \(>\)99\% & & \\  & separation efficiency, good reusability, & & \\  & & high recyclability & & \\ \hline PLA & Oil/water & Superhydrophobic properties, excellent & & \\  & separation & oil absorption capacity, antifouling & & [179] \\  & separation & property, not complicated & \\  & & preparation method & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: An overview of the applications of biodegradable membranes.