A promising research led by an Indian-origin researcher shows that plastic shopping bags - an abundant source of litter on land and at sea - can be converted into diesel, natural gas and other useful petroleum products.
The conversion produces significantly more energy than it requires and results in transportation fuels - diesel, for example - that can be blended with existing ultra-low-sulphur diesels and biodiesels.
Other products, such as natural gas, naphtha (a solvent), gasoline, waxes and lubricating oils such as engine oil and hydraulic oil also can be obtained from shopping bags.
"There are other advantages to the approach, which involves heating the bags in an oxygen-free chamber, a process called pyrolysis," said research leader Brajendra Kumar Sharma, a senior research scientist at the Illinois Sustainable Technology Centre at University of Illinois.
According to Sharma, one can get only 50 to 55 percent fuel from the distillation of petroleum crude oil. But since this plastic is made from petroleum in the first place, we can recover almost 80 percent fuel from it through distillation.
Plastic bags make up a sizeable portion of the plastic debris in giant ocean garbage patches that are killing wildlife and littering beaches.
Plastic bags "have been detected as far north and south as the poles", the researchers wrote.
"Over a period of time, this material starts breaking into tiny pieces, and is ingested along with plankton by aquatic animals," Sharma said.
Fish, birds, ocean mammals and other creatures have been found with a lot of plastic particles in their guts.
"Turtles, for example, think that the plastic grocery bags are jellyfish and they try to eat them," he said. Other creatures become entangled in the bags.
Sharma's team broke the crude oil into different petroleum products and testing the diesel fractions to see if they complied with national standards for ultra-low-sulphur diesel and biodiesel fuels.
"This diesel mixture had an equivalent energy content, a higher cetane number (a measure of the combustion quality of diesel requiring compression ignition) and better lubricity than ultra-low-sulphur diesel," he explained.
The researchers were able to blend up to 30 percent of their plastic-derived diesel into regular diesel, "and found no compatibility problems with biodiesel", Sharma said.
We can just use it as a drop-in fuel in the ultra-low-sulphur diesel without the need for any changes, he added.