Technology to turn plastic waste into diesel
Scientists have found a new way to turn plastic waste into diesel fuel that can be used to run many vehicles and engines.
 |
Plastic waste and nylon bags can be converted into useful fuel. Photo: NanD_PhanuwatTH. |
According to Science Alert, polyethylene is the most common plastic in the world, making up almost everything from food packaging, plastic bottles, plastic films to nylon bags. On average, about 100 million tons of polyethylene plastic are produced each year.
Most of the plastic waste humans produce ends up in landfills, buried underground, or accumulates in the oceans, forming giant floating garbage islands. According to the World Economic Forum in January 2016, the oceans will contain one ton of plastic waste for every three tons of fish by 2025, and there will be more plastic than fish by 2050.
To solve this problem, humans need to turn plastic waste into usable commodities such as liquid hydrocarbon fuels. Polyethylene is made from fossil fuels, but converting polyethylene back to its original composition is a major challenge because plastic is a stable chemical compound.
“If you throw plastic into the ocean or bury it underground, it will remain there for hundreds or even thousands of years,” said Zhibin Guan, a chemist at the University of California, Irvine, USA.
The structure of polyethylene plastic has very stable single-atomic bonds. If the plastic is heated above 400 degrees Celsius, the bonds in the molecules are broken apart in various ways, creating a mixture of gas, oil, wax, and carbon.
To maximize the efficiency of plastic waste treatment as well as control the products created, Guan and his team at the Shanghai Institute of Organic Chemistry, China, invented a plastic recycling technique that consumes less heat.
The scientists mixed the plastic with a catalyst, an organometallic compound. The catalyst was created by mixing existing molecules with the metal iridium. The reaction weakened the plastic's bonds and made it easier to separate. The team then broke down, added to, and rearranged the polyethylene's structure to create a diesel fuel that could be used in electric vehicles and other engines.
The current plastic-to-catalyst ratio is around 30:1, which is close to commercial use. The scientists’ goal is to get this ratio to 10,000:1 in the near future. The process of turning plastic into liquid fuel requires temperatures of around 175 degrees Celsius, much lower than the 400 degrees Celsius required for similar plastic-degrading techniques. The downside is that the chemical reaction is slow and requires expensive catalysts.