Emerging Bioplastic Derived from "Poo Molecule"

Polyether furanoate (PEF) is viewed as a strong candidate among biopolyesters for packaging, by some bioplastics researchers. PEF contains the hydrocarbon, furan, which can be extracted from maize, wood and certain types of grain. Experiments have shown that PEF is superior to standard PET in protecting against oxygen, carbon dioxide and water, resulting in greater product shelf life.

The success of PEF findings by some researchers prompted researchers at Sweden’s Lund University to find other renewable materials that could potentially be used for plastic production. Chemical engineering doctoral student Ping Wang has produced a plastic based on indole, a heavier hydrocarbon molecule than furan, that is present in human feces and smells accordingly. The compound is also found in lower concentrations in certain flowering plants and has a more agreeable aroma. According to the researchers, this effect is due to our sense of smell decoding the aroma differently depending on the amount and combination.

The Lund University research team is believed to be the only one currently researching indole polyesters, and their results are promising. A regular PET bottle’s glass-liquid transition temperature (Tg)–when the material softens and deforms–is 158 F. The most successful PEF experiments withstand about 186.8 F. However, one of Ping Wang’s indole plastics is stable up to 210 F.

“These are preliminary results, but we have seen that this biopolyester has better mechanical properties, which makes it more sustainable. This can lead to better recycling in the future. At present, PET bottles can only be recycled once, then they must be used for something else such as textiles”, says associate professor Baozhong Zhang, who is supervising the research team.

Currently, indole is only produced on a small scale and used mainly in perfumes and drugs. It may be possible to use bioengineering methods to produce indole from sugar through fermentation. However, such a process would first need to be analyzed more thoroughly before the production cost can be calculated.

Meanwhile, Ping Wang is continuing her research by examining the indole plastic’s potential in other application areas.“We obtained good results, but are not satisfied. Now we are trying to find methods for making higher quality indole polymers that can be used in more ways, not just for plastic bottles”, she concludes.