Solar-powered system converts plastic waste into fuel

The University of Cambridge team said the system can convert two waste streams into two chemical products simultaneously.

The reactor converts the carbon dioxide (CO2) and plastics into different products that are useful in a range of industries. In tests, CO2 was converted into syngas, a key building block for sustainable liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry.

The system can also be tuned to produce different products by changing the type of catalyst used in the reactor.

“Converting waste into something useful using solar energy is a major goal of our research,” said professor Erwin Reisner, the paper’s senior author. “Plastic pollution is a huge problem worldwide, and often, many of the plastics we throw into recycling bins are incinerated or end up in landfill.”

The researchers developed an integrated reactor with two separate compartments: one for plastic, and one for greenhouse gases. The reactor uses a light absorber based on perovskite – a promising alternative to silicon for next-generation solar cells.

The team designed different catalysts, which were integrated into the light absorber. By changing the catalyst, the researchers could then change the end product.

Tests of the reactor under normal temperature and pressure conditions showed that the reactor could efficiently convert PET plastic bottles and CO2 into different carbon-based fuels such as CO, syngas or formate, in addition to glycolic acid. It produced these products at a rate that is also much higher than conventional photocatalytic CO2 reduction processes.

“Generally, CO2 conversion requires a lot of energy, but with our system, basically you just shine a light at it, and it starts converting harmful products into something useful and sustainable,” said co-first author Dr Motiar Rahaman.

“Prior to this system, we didn’t have anything that could make high-value products selectively and efficiently.”

The team recently received new funding from the European Research Council to help the development of their solar-powered reactor.

Over the next five years, they hope to further develop the reactor to produce more complex molecules and believe that similar techniques could someday be used to develop an entirely solar-powered recycling plant.

“Developing a circular economy, where we make useful things from waste instead of throwing it into landfill, is vital if we’re going to meaningfully address the climate crisis and protect the natural world,” said Reisner. “And powering these solutions using the Sun means that we’re doing it cleanly and sustainably.”