Although hydrogen production is seen as a potential replacement for fossil fuels, the processes either produce too much carbon dioxide or are too expensive. A low-emission technique for producing hydrogen from plastic garbage has been developed by Rice University researchers, which could pay off handsomely.
“In our study, we converted waste plastics, including mixed waste plastics that do not need to be sorted or washed, into highly efficient hydrogen gas and high-value graphene,” said Kevin Wyss, lead author of the study. “Clean hydrogen could be produced for free if the graphene produced was sold for just 5% of its current market value – selling at a 95% discount!”
By contrast, “green” hydrogen costs around $5 for just over two kilos and is produced using renewable energy sources to split water into its two components. Although more affordable, most of the more than 2022 million tonnes of hydrogen used globally in 100 came from fossil fuels, with each tonne of hydrogen produced producing approximately 12 tonnes of carbon dioxide.
Rice University Researchers explained that the main type of hydrogen used today is “gray” hydrogen, created by the steam-methane reforming process that produces a lot of carbon dioxide. If we are serious about achieving net zero emissions by 2050, we cannot continue to produce hydrogen in the way we have done so far, as demand for hydrogen is predicted to increase in the coming decades.
The researchers subjected samples of plastic trash to rapid Joule heating for about four seconds, raising their temperatures to 3.100 degrees Kelvin. In this process, the hydrogen in the polymers evaporated, leaving behind graphene, an incredibly light and strong single layer of carbon atoms.
“When we first discovered flash Joule heating and applied it to convert waste plastic into graphene, we observed that a lot of volatile gases were produced and rushed out of the reactor,” added Wyss. “We wondered what these were, suspecting a mixture of small hydrocarbons and hydrogen, but we lacked the instrumentation to study their exact composition.”
The Tour laboratory was able to purchase the necessary tools to characterize the vaporized content thanks to support from the United States Army Corps of Engineers.
“We have shown that we can recover up to 68% of this atomic hydrogen as gas with 94% purity, and we know that polyethylene, for example, consists of 86% carbon and 14% hydrogen,” Wyss added. “Developing methodologies and knowledge to characterize and quantify all gases, including hydrogen, produced with this technology has been a challenging but rewarding task for me.
“I am pleased that the skills I have acquired and used in this job, particularly gas chromatography and life cycle assessment, can be applied to other projects within our organisation. I hope that this work will make it possible to produce clean hydrogen from used plastic bottles, solving important environmental problems such as plastic pollution and high greenhouse gas emissions of the steam methane reforming method.
📩 15/09/2023 10:50