Quantum simulation for solving the waste plastics problem

 
Plastics are ubiquitous, convenient, and cheap. So, it is not a surprise that the world manufactures 359 million metric tons (Garside, 2020) of plastics every year. Most plastics are yet not readily biodegradable. As a result, at the end of life, 55% (Ritchie and Roser, 2018) of all waste plastics find their way into landfills, or are illegally dumped into oceans, freshwater sources, and wildlife habitats. The damage is, thus, catastrophic and often irreversible.

Researchers are investigating many creative solutions to reduce the impact of waste plastics. From a chemical point of view, the primary elements that make all plastics are hydrogen and carbon, the same elements that make the hydrocarbon fuels. Turning waste plastics into fuel sources seems to be a solution that could work. But how can weconvert waste plastics to fuel safely?

Breaking up the long molecular chain of the plastics into the smallest hydrocarbon molecules, like methane and ethane of natural gas, seems to be the way to go. Controlled thermal degradation at temperatures exceeding 1500 °C may achieve this goal. But it is imperative that no toxic or polluting fumes and by-products such as dioxins are produced along the way. Molecular dynamics simulations based on the principles of quantum mechanics (ab initio) can accurately predict how the plastic chains break up at high temperatures and pressures. The insight from these simulations provides a fundamental understanding that aids experimental trials and helps the safe industrial implementation of the plastic-to-fuel process.

Many energy-intensive industrial processes, say steelmaking, already happen at high temperatures. By bringing insight from the quantum simulations to the steelmaking process, we can take advantage of the furnace’s heat and convert waste plastics to fuel on the spot.

Various European plants (Devasahayam et al., 2019) are currently integrating the waste-to-fuel process with steelmaking, achieving low-waste circular economy and industrial symbiosis (Branca et al., 2020) across different technologies where multiple industrial sectors work together to reduce plastic waste. By adding carbon capture technology (Jiang et al., 2020) to the mix, traditionally polluting but indispensable industries, like steelmaking, can vastly reduce their carbon footprint. Modern quantum simulation techniques can definitely expand the domain of this symbiosis to include waste electronics, automotive waste, and much more in the future.