Turning plastic waste into low-cost hydrogen fuels

Because the impacts of the continued local weather disaster and environmental challenges like air pollution and ecosystem degradation turn out to be more and more evident, the necessity for revolutionary options that deal with these complicated points on a number of fronts grows extra pressing.

In a latest examine revealed in Superior Supplies, researchers led by Boris Yakobson and James Tour from the Division of Supplies Science and NanoEngineering at Rice College within the US are doing simply this with a brand new expertise that converts waste plastic into clear hydrogen fuel and high-purity graphene with none carbon dioxide (CO₂).

“What if we turned waste plastic into one thing far more precious than recycled plastic whereas on the identical time capturing the hydrogen that’s locked inside?” requested Kevin Wyss, a chemist at SLB (previously referred to as Schlumberger) who accomplished the challenge as a part of his Ph.D. thesis.

This concept led to a transformative resolution that not solely mitigates environmental hurt but additionally harnesses untapped worth from problematic waste supplies.

The will for hydrogen

Hydrogen stands out as a clear and enticing gasoline supply as a consequence of its skill to yield substantial power per unit weight whereas producing water as its sole byproduct. “That is what makes it sustainable or ‘inexperienced’ in comparison with present fuel, coal, or oil fuels, which emit a lot of CO₂.” mentioned Wyss. “And in contrast to batteries or renewable energy sources, hydrogen may be saved and re-fueled rapidly with out ready hours to cost. Because of this, many vehicle producers are eager about transitioning to hydrogen gasoline.”

In 2021, the worldwide consumption of hydrogen reached a staggering 94 million tonnes, and demand is projected to surge within the coming decade. Nonetheless, the dilemma lies in the truth that, regardless of hydrogen’s popularity as a inexperienced gasoline, the dominant methodology of hydrogen manufacturing nonetheless depends on fossil fuels by a course of referred to as steam-methane reforming, which isn’t solely power intensive, however leads to CO₂ emissions as a byproduct. “Actually, for each ton of hydrogen made industrially proper now, 10-12 tons of CO₂ are produced,” mentioned Wyss.

An rising various is to provide hydrogen fuel by a course of referred to as electrolysis, the place water is break up into its constituent parts utilizing electrical energy. Whereas the electrical energy supply may be renewable, similar to photo voltaic, wind, or geothermal power, guaranteeing this stays a problem. These processes additionally require extra supplies, similar to catalysts, and price round $3-5 USD per kg of hydrogen, making it troublesome to compete with the reforming course of at ~$2 USD per kg.

“You’ll be able to see why we want strategies to provide hydrogen in an environment friendly and low-cost methodology that doesn’t produce massive quantities of CO₂,” mentioned Wyss.

The issue with plastics and hydrogen fuels

Wyss defined that the challenges posed by plastic waste air pollution and low-carbon hydrogen manufacturing are issues that scientists have efficiently addressed a long time in the past.

“Within the case of plastic waste air pollution, we all know how one can recycle plastics — the issue lies in the truth that recycling is so costly, with the excessive prices of manually separating plastic sorts, washing the waste, after which re-melting the polymers,” he mentioned. “In consequence, recycled plastics usually value greater than new plastics, so there’s not an financial incentive to recycle and thus, air pollution remains to be an issue a long time later.

“Within the case of hydrogen manufacturing, we all know how one can make hydrogen gasoline with out producing CO₂, however is 2 to 3 instances costlier than strategies that produce hydrogen with a lot of CO₂.”

Therefore, the true problem lies not in fixing these issues, however moderately discovering methods to scale back the price of their options — a problem Wyss and his colleagues are tackling head on.

Flash Joule heating breaks down plastics

Their strategy makes use of flash Joule heating, a cutting-edge approach for quickly heating supplies to extraordinarily excessive temperatures. To attain this, an electrical present is run by a fabric that has electrical resistance, which swiftly converts the electrical energy into warmth, reaching temperatures of 1000’s of Kelvins in mere seconds.

“We discharge present by the pattern of plastic, with a small quantity of added ash to make it conductive, and obtain temperatures as much as 2,500°C inside a tenth of a second, earlier than the pattern cools again down inside a number of seconds,” mentioned Wyss. “This speedy heating reorganizes the chemical bonds within the plastic — the carbon atoms within the plastic convert to the [carbon-carbon] bonds of graphene, and the hydrogen atoms convert to H₂ [gas].”

“This course of upcycles the waste plastics with excessive effectivity utilizing no catalyst or different solvents,” he continued. “As soon as our plastics have undergone the response, we additionally get pure, precious graphene, used for strengthening automobiles, cement, and even making versatile electronics and touchscreens, and which at the moment has a worth of $60,000-$200,000 per ton.”

Wyss says that his lab at Rice College has been engaged on flash Joule heating for the previous 5 years, however their major focus was beforehand on making graphene from plastics. However he says that, after a while, they realized that many plastic polymers additionally include atomic hydrogen. “If we find yourself with graphene, which is 100% pure carbon, the place is all of the atomic hydrogen locked within the plastic going?” he requested.

They due to this fact set about trapping and finding out the risky gases emitted throughout their flash Joule heating course of, and to their shock found they have been liberating nearly 93% of the atomic hydrogen and have been in a position to get well as much as 64% of it as pure hydrogen — yields which can be akin to present industrial strategies that emit 5 to 6 instances extra CO₂.

“Our methodology produces 84% much less CO₂ and greenhouse gases per ton of hydrogen produced, in comparison with the present in style industrial methodology of steam methane reforming, […] and makes use of much less power than present ‘inexperienced’ hydrogen manufacturing strategies, similar to electrolysis,” Wyss mentioned.

Making an EarthShot

This aligns with the US Division of Vitality’s EarthShot Initiative, modeled after the historic “Moonshot Problem”, which aimed to place a person on the moon within the Nineteen Sixties. Equally, the EarthShot initiative seeks to mobilize sources and creativity to realize formidable environmental objectives.

These objectives are meant to be scalable, achievable, and designed to deal with crucial points associated to local weather change, biodiversity loss, air pollution, and different environmental crises. “The local weather disaster requires a special form of moonshot,” they wrote on the web site. “Vitality Earthshots [such as the Hydrogen Shot] will speed up breakthroughs of extra considerable, reasonably priced, and dependable clear power options inside the decade.”

The objective is to make 1kg of fresh hydrogen value $1 USD inside the subsequent decade, the place clear hydrogen is outlined as any that’s produced with much less then 4 kg of CO₂ as a byproduct.

“Our analysis has proven that we are able to do this now, if the [flash Joule heating] course of is scaled up, changing waste plastics into clear hydrogen and graphene,” mentioned Wyss. “At present, 95% of hydrogen produced globally leads to 10-12 kg of CO₂ being produced as a byproduct. Our course of produces as little as 1.8 kg of CO₂ per kg of hydrogen.”

Earlier than this could occur, Wyss acknowledges that scale-up remains to be a problem. As hydrogen is a flammable fuel, its protected seize and purification requires some cautious planning and engineering. However Wyss is hopeful it may be finished.

“An organization named Common Matter was began three years in the past to scale-up the flash Joule heating course of to make graphene,” Wyss mentioned. “In that brief time, [they have] scaled from gram-per-day ranges to ton-per-day graphene manufacturing. So, we’re very optimistic that this hydrogen manufacturing methodology may be equally scaled efficiently because the core ideas are similar.”

Reference: Boris I. Yakobson, James M. Tour, et al., Synthesis of Clear Hydrogen Fuel from Waste Plastic at Zero Web Value, Superior Supplies (2023). DOI: 10.1002/adma.202306763

Function picture credit score: tanvi sharma on Unsplash