About 12 billion metric tons of plastic waste will be sitting in landfills or in the natural environment by 2050. To stop that deluge, and its associated carbon emissions, we’ll need many solutions. But a key one would be plastics that are not only made from sustainable non-petroleum sources but are also easy to recycle back into high-quality plastic. A new plastic made by researchers at the University of Konstanz in Germany could be just the answer. It is a type of polyethylene—the world’s most commonly used plastic—made from plant and microalgae oils, and that can be recycled with near-perfect efficiency. The recycling method, also reported in the journal Nature, requires relatively low temperatures, making it more energy-efficient, and also recovers 96 percent of the starting material.
Polyethylene is the stuff of shopping bags and water bottles. The world makes millions of tons of it every year but a small percentage is recycled. That’s partly due to lacking recycling infrastructure, but also because today’s mechanical recycling techniques which involve chopping up the plastic and then melting and reforming it give material of lower quality. So recycled polyethylene is often used to make products such as rugs instead of reformed into plastic water bottles.
But there’s an alternative recycling technique called chemical recycling. This technique involves breaking the bonds in plastics, which are long chains made of smaller, simpler molecules, to separate those smaller molecules that can be restrung into new high-quality plastic. The problem is this process requires temperatures over 600°C, making it energy-intensive. And it recovers a limited amount of the starting material, sometimes less than ten per cent.