Green hydrogen succefully produced from plastic waste

Kevin Wyss/Tour lab 

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Green hydrogen succefully produced from plastic waste

Climate change has made scientists seek renewable energy where it can be found. While manufacturing products out of waste is on the way to becoming a mainstream practice, producing hydrogen from waste is the first we’ve heard of.

Recently, a team of scientists from Rice University successfully harvested hydrogen – a sustainable alternative to fossil fuels from plastic waste.

Usually, methods used to produce hydrogen are often unsustainable, while the energy itself may be. Such methods are known to generate carbon emissions and are also costly to produce. 

However, this new technique is a low-emissions strategy that could more than pay for itself, according to a statement by the researchers.

Kevin Wyss, a Rice University’s doctoral alumnus and lead author of the study, said that the team 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.

“If the produced graphene is sold at only five percent of current market value ⎯ , a 95 percent off sale! ⎯ clean hydrogen could be produced for free,” Wyss expressed.

Green hydrogen, derived from renewable energy sources, which experiences a process of water splitting into two components, is priced at approximately $5 for slightly more than two pounds.

In comparison, the majority of 100 million tons of hydrogen consumed globally in 2022 was was produced from cheaper fossil fuels. Still, the production had approximately 12 tons of carbon dioxide per ton of hydrogen.

James Tour, Rice’s T. T. and W. F. Chao Professor of Chemistry and a professor of materials science and nanoengineering, noted:

“The main form of hydrogen used today is ‘gray’ hydrogen, produced through steam-methane reforming, a method that generates a lot of carbon dioxide. Demand for hydrogen will likely skyrocket over the next few decades, so we can’t keep making it the same way we have until now if we’re serious about reaching net zero emissions by 2050.”

The scientific process of creating hydrogen from plastic waste material involves exposing the waste samples to rapid flash Joule heating for nearly four seconds. This brought the temperature up to 3100 degrees Kelvin. 

Consequently, the procedure vaporizes the hydrogen within plastics, forming graphene — a remarkably lightweight and robust material composed of a single layer of carbon atoms.

Wyss explained that when the flash Joule heating technique was first discovered and then utilized to upcycle waste plastic into graphene, scientists noticed the production of many volatile gases and them being shot out of the reactor. 

“We wondered what they were, suspecting a mix of small hydrocarbons and hydrogen, but lacked the instrumentation to study their exact composition.”

To analyze the vapourised content, the team acquired the necessary equipment to determine hydrogen production. 

The scientists recovered 68 percent of the atomic hydrogen despite having a purity of 94 percent.

Wyss described: “We know that polyethylene, for example, is made of 86 percent carbon and 14 percent hydrogen. 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 highlighted other new techniques employed in the research and development of low-emission-generating hydrogen, including life-cycle assessment and gas chromatography. 

“I hope that this work will allow for the production of clean hydrogen from waste plastics, possibly solving major environmental problems like plastic pollution and the greenhouse gas-intensive production of hydrogen by steam-methane reforming.”

The study was published in the journal – Advanced Materials on September 11. 

Green hydrogen succefully produced from plastic waste

Hydrogen Production By Steam Reforming Of Natural Gas Hydrogen gas (H2) is the primary storable fuel for pollution-free energy production, with over 90 million tonnes used globally per year. More than 95% of H2 is synthesized through metal-catalyzed steam methane reforming that produces 11 tonnes of CO2 per tonne H2. “Green H2” from water electrolysis using renewable energy evolves no CO2, but costs 2–3x more, making it presently economically unviable. Here  we report catalyst-free conversion of waste plastic into clean H2 along with high purity graphene. The scalable procedure evolves no CO2 when deconstructing polyolefins and produces H2 in purities up to 94% at high mass yields. Sale of graphene byproduct at just 5% of its current value yields H2 production at negative cost. Life-cycle assessment demonstrates a 39–84% reduction in emissions compared to other H2 production methods, suggesting the flash H2 process to be an economically viable, clean H2 production route.