The recent success of bio-plastic polyethylene furanoate (PEF), which instead of common oil-based polyethylene terephthalate (PET) uses the hydrocarbon compound furane extracted from, among others, maize, wood and cereals, prompted experiments with other renewable materials in plastic production at Lund University.
A scientific group led by Baozhong Zhang, associate professor at Lund University's Centre for Analysis and Synthesis, has developed a "green" fossil-free bio-polyester that lab experiments have proven is more durable than both ordinary plastic and other bioplastics, as well as potentially better suitable for recycling, the scientific portal Forskning.se reported.
Indolepolyester, created by Zhang's PhD student Ping Wang, is claimed to be superior to both PET and PEF in many ways. Unlike PET and PEF, which decompose at 70 to 86 degrees Celsius, Wang's indole plastic can withstand a temperature of 99 degrees and allows for endless recycling.
"What we have seen is that indole has better mechanical properties that make it more durable. This can lead to better recycling in the future. At present, PET bottles can only be recycled once, then they must be used for other things, such as textiles", associate professor Baozhong Zhang told Forskning.se.
Although based on indole, a substance produced by several bacteria and known for its heavy faecal stench, the new bio-polyester is completely odourless.
"Once you make this into a plastic, it changes completely and it doesn't have any smell", Zhang assured the news outlet The Local, lamenting the fact that indole was previously largely ignored by the scientific community as a sustainable source of plastics.
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Today, indole is only produced on a small scale and is mainly used in perfume and pharmaceuticals. However, mass production of indole from sugar by fermentation using bacteria is fully possible. Still, such a process must first be analysed in detail before calculating production costs.
Despite being present in faeces, this does not mean sewage works will become the plastic factories of the future. According to Zhang, indole can also be made from various resources in nature, such as amino acids and numerous plants.
Currently, almost all plastic is made from fossil fuels (mostly crude oil). Today, plastic production accounts for six percent of global oil consumption. A switch to green technology would thus alleviate the carbon footprint.