# Harnessing Agri-Food Waste as a Source of Biopolymers for Agriculture
## 2 Sources of Biopolymers
### Polylactic Acid (PLA): A Non-Toxic Alternative for Mulching Films and Food Packaging
The use of lignocellulosic waste such as wood flour [125; 126], cork [125], rubber wood sawdust [127], bark [128], spinach stems, tomato pomace, cocoa shells [122], and orange peels [129] as fillers in PLA films successfully improved its mechanical characteristics. Poly (lactic acid) (PLA) is a biodegradable, bio-based polymer that has attracted a lot of attention as an alternative to conventional petroleum-based plastics [112]. However, it is not the only sustainable alternative. Others include polybutylene succinate (PBS) and polybutylene adipate terephthalate (PBAT), which have several advantages and limitations compared to PLA [130; 131]. PBS is a biodegradable polyester that has properties similar to polypropylene. It is derived from succinic acid and 1,4-butanediol, which can be produced from renewable resources. PBS offers good thermal and mechanical properties, making it suitable for various applications, such as packaging films, bags, and disposable items. One advantage \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Entry** & **Biomass** & \
\begin{tabular}{c} **Biomass** \\ **Pretreatment** \\ \end{tabular} & **Saccharification** & **LA Producer** & **Yield** &
\begin{tabular}{c} **LA Titer** \\ **(g/L)** \\ \end{tabular} & **Ref.** \\ \hline
1 & Grape (_Vits vinifera_) stalks & \begin{tabular}{c} Steam \\ explosion \\ \end{tabular} & \
\begin{tabular}{c} Enzymatic saccharification \\ \end{tabular} &
\begin{tabular}{c} _Lactobacillus thammosus_ \\ IMC501 \\ \end{tabular} & 0.98 & 20 & [116] \\ \hline
2 & Olive (_Olar europara_) pits & Diluted acid (H\({}_{2}\)SO\({}_{4}\)) & _Bacillus coagulans_ DSM2314 &
\begin{tabular}{c} 0.71 \\ \end{tabular} & 61.3 & [117] \\
3 & \begin{tabular}{c} Sugarcane (_Saccharum_ \\ _officiarum_ L) bagasse \\ \end{tabular} & \
\begin{tabular}{c} Hydrothermal \\ hydrolysis \\ \end{tabular} & _Bacillus coagulans_ DSM2314 &
\begin{tabular}{c} 0.66 \\ \end{tabular} & 52.4 & \\ \hline
4 & \begin{tabular}{c} Potato (_Salamum tuberosum_) \\ peel waste \\ \end{tabular} & \
\begin{tabular}{c} _Rilizopus oryzae_ (CBP) \\ \end{tabular} &
\begin{tabular}{c} 0.039 \\ \end{tabular} & 3.14 & [118] \\ \hline
5 & \begin{tabular}{c} Corncob (_Zan mays_) \\ Residue \\ \end{tabular} & \begin{tabular}{c} Alkali \\ pretreatment \\ \end{tabular} & \
\begin{tabular}{c} _Clestridium_ \\ _thermocellum_ \\ ApyrF:p2638-BGL \\ BGL \\ \end{tabular} &
\begin{tabular}{c} 0.74 \\ _starothermophilus_ 2H-3 \\ \end{tabular} & 51.36 & [119] \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Biotransformation of biomass in LA. of PBS over PLA is its greater flexibility and strength, which can be an advantage in certain applications. However, PBS biodegrades at a slower rate than PLA and can be more expensive to produce [130]. PBAT, on the other hand, is another biodegradable polyester that is often used in blends with PLA to improve its flexibility and strength [132]. PBAT is synthesized from adipic acid, 1,4-butanediol, and terephthalatic acid, all of which can be obtained from renewable resources. PBAT offers good flexibility and elongation properties [132], making it suitable for applications that require elasticity [131], such as compostable bags and films [130]. Compared to PLA, PBAT generally has better elongation at break and toughness. However, depending on the specific formulation, it may have lower stiffness and heat resistance than PLA [130]. Although both PBS and PBAT offer advantages over PLA in terms of certain mechanical properties and flexibility, they can also present challenges, such as slower biodegradation rates, higher production costs, and potential compatibility issues in blends [130]. In addition, the choice between these polymers often depends on application-specific requirements, including mechanical performance, biodegradability, and cost considerations. However, PLA is currently most used in agricultural applications due to its high biodegradability and biocompatibility, making it more suitable for sustainable agricultural applications [130].