By now, we all know that plastic waste is a huge problem. More than 350,000,000 tons of plastic waste are generated annually, resulting in devastating ecological impacts. Many of these plastics break down into microplastics, small plastic pieces less than 5mm long. Microplastics often enter marine environments and are eaten by fish and other aquatic animals, which harms the entire ecosystem.
Recycling has helped to make a dent in the amount of plastic that is dumped into landfills. The most common ways to recycle plastic include transformation of the plastic into other products and combustion. While it is a popular way to stop plastic waste from entering ecosystems, burning plastic can release toxic chemicals into the atmosphere. Researchers have tried to adapt to this, experimenting with ways to harness the energy from burning plastic waste through pyrolysis.
Pyrolysis is the process of heating carbon-based material in the absence of oxygen, in an attempt to create fuels or other beneficial chemical compounds. At different pyrolysis temperatures, you can recover different ratios of products: at lower temperatures (around 500 °C), more wax and char are created during the process. When the temperature is raised over 700 °C, however, products were made with almost identical properties to gasoline.
A new study in the Journal of Renewable and Sustainable Energy from the American Institute of Physics explores more efficient ways to carry out pyrolysis since the high temperatures needed to carry out this process are expensive and resource-consuming. Using plastic bags commonly found in grocery stores, researchers introduced a catalyst that decreased the reaction temperature and increased the efficiency of breaking down the plastics.
The catalyst was developed in a lab and was able to operate at atmospheric pressure. They also used a lab-designed catalytic reactor, but the synthesis of the catalyst itself is inexpensive. Using the catalyst and reactor to break down plastic bags, they were able to yield a product containing a range of C9-C22 hydrocarbons, similar to what’s found in the base of diesel fuel. On top of that, the pyrolysis was effective at 360 °C.
This study also included an economic analysis of their procedure. They calculated that producing and selling the product as diesel fuel at market prices (an average of $3.09 per gallon in 2019) has the potential to produce about $3,000,000 worth of fuel per year. If the product is used to power a generator, it could produce around 38,000 kW h of electricity per day.
The process of catalyst-based pyrolysis still needs to be refined, but this study is a definite step forward in creating more sustainable fuels from everyday waste.
Sources: American Institute of Physics