Scientists at Washington State University in the US have found a new way to recycle plastic waste products into valuable fuel for aircraft.
Plastic scrap can be melted at high temperature of around 570 degrees Celsius (or 1 060 degrees Fahrenheit) with ‘activated carbon’ to produce jet fuel. A series of experiments at Washington State University (WSU) has been conducted using low-density as well as high-density polyethylene products such as milk bottles and plastic bags.
‘Hard to break down’
These were ground to around three millimetres, or about the size of a grain of rice. Associate professor Dr Hanwu Lei notes; ‘Plastic is hard to break down. You have to add a catalyst to help break the chemical bonds. There is a lot of hydrogen in plastics, which is a key component in fuel.’
Lei, who is with the WSU department of Biological System Engineering, explains that the carbon is a catalyst that speeds up a chemical reaction without being consumed by the reaction. Once the carbon catalyst has done its work, it can be separated out and re-used on the next batch of waste plastic conversion. The catalyst can also be regenerated after losing its activity.
After testing several different catalysts at different temperatures, the best result produced a mixture of 85% jet fuel and 15% diesel fuel. The scientists were also able to recover almost 100% of the energy from the plastic used in the tests.
High quality fuel
‘The fuel is very good quality, and the by-product gases produced are high quality and useful as well,’ says Lei. This breakthrough is seen as representing a ‘very good’ and ‘relatively simple’ method to recycle low-density and high-density plastics.
Results indicate that the innovative process can easily be scaled up. For example, it could help farmers transform plastic waste into diesel. ‘You have to separate the resulting product to get jet fuel. If you don’t separate it, then it’s all diesel fuel,’ the scientist argues.
The research has been published in the journal Applied Energy.
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