Plastic waste is one of the biggest issues facing the planet today, with its impact stretching far and wide. It can be found polluting the tallest mountains to the deepest ocean trenches; plastic waste can affect human health, destroy ecosystems, and harm wildlife especially marine species.

The plastic waste problem has been aggravated in recent decades as global plastics production has doubled since the beginning of the century, to almost 400 million metric tons per year in 2021 and is projected to triple by 2060, to a staggering one billion metric tons. While the lifespan of plastic products averages around 10 years, plastics can take up to 500 years to decompose, depending on their composition and disposal according to the global data and business intelligence platform of Statista.

Thus, environmental activists strive to find alternatives to the different plastic products to lessen environmental pollution. Given the difficulty of lessening dependence on plastic products, American scientists from Rice University, Texas, managed to turn plastic from a problematic substance into a profitable source of energy.

According to the study, recently revealed by Rice University, scientists have found a way to harvest hydrogen from plastic waste using a low-emissions method that could more than pay for itself.

“In this work, we converted waste plastics ⎯ including mixed waste plastics that don’t have to be sorted by type or washed ⎯ into high-yield hydrogen gas and high-value graphene,” said Kevin Wyss, a Rice doctoral alumnus and lead author on a study published in Advanced Materials. “If the produced graphene is sold at only 5% of current market value ⎯ a 95% off sale! ⎯ clean hydrogen could be produced for free,” he added.

In this study, the researchers exposed plastic waste samples to rapid flash Joule heating for about four seconds, bringing their temperature up to 3,100 degrees Kelvin. The process vaporizes the hydrogen present in plastics, leaving behind graphene ⎯ an extremely light, durable material made up of a single layer of carbon atoms.

“When we first discovered flash Joule heating and applied it to upcycle waste plastic into graphene, we observed a lot of volatile gases being produced and shooting out of the reactor,” Wyss said. “We wondered what they were, suspecting a mix of small hydrocarbons and hydrogen, but lacked the instrumentation to study their exact composition.”

Thus, the researchers resorted to the US Army Corps of Engineers to Acquire the necessary equipment to characterize the vaporized contents.

“We know that polyethylene, for example, is made of 86% carbon and 14% hydrogen, and we demonstrated that we are able to recover up to 68% of that atomic hydrogen as gas with a 94% purity,” Wyss said. “Developing the methods and expertise to characterize and quantify all the gases, including hydrogen, produced by this method was a difficult but rewarding process for me.”

Wyss believes that their work can potentially lead to the production of clean hydrogen from plastic waste solving the environmental issues of plastic waste pollution and the great greenhouse gas emissions from hydrogen production through steam-methane reforming.

Hydrogen is viewed as a promising alternative to fossil fuels. According to the International Energy Agency (IEA), hydrogen demand worldwide reached 95 million tons in 2022 and is set to be more than 150 million tons by 2030.

However, the methods used to produce hydrogen either generate too much carbon dioxide or are too expensive.

The significance of this study is not limited to idealist utilization of plastic wastes for production of hydrogen, but also in doing this at much cheaper rates than that obtained from renewable sources of energy and with low emissions.

Meanwhile, green hydrogen ⎯ produced using renewable energy sources to split water into its two component elements ⎯ costs roughly $5 for just over two pounds.

Though cheaper, most of the nearly 100 million tons of hydrogen used globally in 2022 was derived from fossil fuels, its production generating roughly 12 tons of carbon dioxide per ton of hydrogen according to the American study.

“The main form of hydrogen used today is ‘gray’ hydrogen, which is produced through steam-methane reforming, a method that generates a lot of carbon dioxide,” said James Tour, Rice’s T. T. and W. F. Chao Professor of Chemistry and a professor of materials science and nanoengineering. “Demand for hydrogen will likely skyrocket over the next few decades, so we can’t keep making it the same way we have up until now if we’re serious about reaching net zero emissions by 2050.”

Green Hydrogen has received special attention as a zero-emission fuel in fuel cells and internal combustion engines. In addition, hydrogen is essential for converting industrial CO2 emissions into platform chemicals such as methanol, which prevents CO2 from being released into the atmosphere.

However, most of the current global hydrogen production comes from coal gasification and steam methane reforming. Both processes are accompanied by large CO2 emissions and must be avoided in order to comply with restrictions on Greenhouse Gas (GHG) emissions. Hence, calls were made to produce green hydrogen from renewable so as to limit harmful emissions.