In a ground-breaking discovery, researchers in India have developed a relatively low-temperature process to convert certain plastic waste into liquid fuel.
This discovery may lead to re-using discarded plastic bags and other products to address growing demands for fuel globally, said a study, to be published in International Journal of Environment and Waste Management.
Chemist Achyut Kumar Panda of Centurion University of Technology and Management Odisha, and chemical engineer Raghubansh Kumar Singh of National Institute of Technology, Orissa, developed a commercially viable technology for efficiently rendering common polymer, low-density polyethylene (LDPE) into a liquid fuel.
LDPE is used to make container, medical and laboratory equipment, computer components and plastic bags.
In their approach, the team heat up the plastic waste to between 400 and 500 degrees
celsius over a kaolin catalyst (a clay mineral containing aluminum and silicon).
This caused the plastic's long chain polymer chains to break apart in a process known as thermo-catalytic degradation.
The process released large quantities of much smaller, carbon-rich molecules.
"We used an analytical method called Gas chromatography-mass spectrometry (GC-MS) to characterise these product molecules and found the components of their liquid fuel to be mainly paraffins and olefins 10 to 16 carbon atoms long," explained Panda.
This makes the liquid fuel very similar chemically to conventional petrochemical fuels, he added.
Kaolin acts as a catalyst by providing a large reactive surface on which the polymer molecules can sit and so be exposed to high temperature inside the batch reactor, which breaks them apart.
"We could boost the yield to almost 80 percent and minimize reaction times in further tests," said Singh.
Recycling initiatives are in place across the world but much of the polyethylene waste ends up in landfill, dispersed in the environment or in the sea.
The process, if implemented on a large scale, can reduce pressures on landfill as well as ameliorating the effects of dwindling oil supplies in a world with increasing demands on petrochemicals for fuel, contended the study.
