From plastic to hydrogen with microwaves

Written by Theo Koenig - October 21, 2020

The latest stride towards a greener future comes from a study published in Nature Catalysis, offering the promise of exposing plastic waste to microwaves and thereby creating hydrogen. The one-step process extracts up to 97% of the hydrogen present in plastic in a short time, at a low cost, and without creating CO2.

According to the study, 4.9 billion tons of plastic have been produced to date and by 2050, the figure is expected to reach 12 billion. These frightening statistics are what motived the researchers at the Oxford department of chemistry to convert plastic polymers into something beneficial in the form of a renewable fuel. As detailed in the study, plastic can be composed of anywhere between 8% to 14% of their total weight in hydrogen. Microwaves are used to activate the catalyst particles to “effectively strip hydrogen from the polymers”.

Plastic waste from milk containers, foam, plastic bags, and food wraps from large supermarket chains were used in the study. These polymers were then mechanically pulverized and mixed with an iron and aluminum oxide catalyst (FeAlx), which when subject to microwave treatment, creates large volumes of hydrogen gas while only leaving a residue of carbonaceous materials. This remaining high-value carbon comes in the form of multi-walled nanotubes which are typically ideal for enhancing various kinds of structures in the form of material dampening or enhancing stiffness.

The procedure takes roughly 30 to 90 seconds, and unlike previous studies, is a one-step process. Experiments from the past were very promising but produced large volumes of CO2 while also requiring considerable energy input. Such existing approaches revolved around heating the plastic (to roughly 750°C), generating a hydrogen and carbon monoxide mixture and then, in a second step, separating out the hydrogen. The current study has the advantage of just heating the catalyst and not the plastic (as plastic does not absorb microwaves), which results in far lower energy requirements.

Auto Trendy's take:

Plastic waste treatment has certainly come a long way during the past decade. Plastic Park, for instance, is the UK’s first plastic to hydrogen facility and announced a few weeks ago the completion of the first stage of development. Depending on how this first plant continues, it is reported that an additional 11 facilities will be constructed in the coming years. Considering the enormous rate of plastic consumption, most alternate solutions to landfills and oversees exportation will be met with opens arms. That being said, it remains to be seen whether scientific breakthroughs such as these can become scalable. At Auto Trendy we are big believers in the future of hydrogen as a replacement for fossil fuels in the automotive industry. However, two main hurdles still need to be addressed: the high energy requirements needed to convert vast volumes of hydrogen gas to liquid hydrogen, and the creation of an adequate hydrogen charging infrastructure. While it may take years, even decades before we begin to regularly see hydrogen-powered vehicles, the promising signs are clearly visible.