Hydrogen Fuel from Waste Plastic

The following is excerpted from a Rice University news release and a MIT news release:

In the early 21st century vehicles using hydrogen-powered fuel cells rivaled electric vehicles with batteries (EVs) as the best way to decarbonize the car industry by replacing gasoline. Today, EVs are way ahead and IRA has clearly chosen their winner- EVs. The big car companies are trying to rapidly electrify their vehicle offerings, but are facing resistance from the consumer. On of the resistant is my husband who really wants a hydrogen car.

Research at MIT found that the lifetime cost of ownership for a fuel cell car has come down in recent years, but remains higher than EVs largely because of the cost of hydrogen fuel. The researchers found the total cost of ownership for hydrogen was around 40% higher than a comparable gasoline vehicle, and about 10% higher than an EV.

EVs have another crucial advantage over hydrogen. There already exists a vast nationwide electrical system. A nationwide transition to electric vehicles creates big challenges, including the need to build a charging network and make plenty of extra electricity to power all these cars and trucks. 

Hydrogen has its own advantages. The fuel can be pumped in less time than it takes to charge an EV battery, and it can deliver longer driving ranges more in line with gasoline cares. Hydrogen more closely resembles the pump-and-go experience everyone knows from using gasoline. However, that experience would require creating an enormous amount of hydrogen and then moving itto refueling stations all over the country. 

Innovations to make hydrogen cleaner and cheaper could help make fuel cell vehicles competitive once again and possibly more desirable. Until now the methods used to make hydrogen it either generate too much carbon dioxide or are too expensive. Green hydrogen, produced using renewable energy sources to split water into its two component elements, costs roughly $5 for just over two pounds.

"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, a materials scientist. Most of the nearly 100 million tons of hydrogen used globally in 2022 was grey hydrogen derived from fossil fuels, and its production generated roughly 12 tons of carbon dioxide per ton of hydrogen.

Recently researchers from Rice University (James Tour and Kevin Wyss) have found a way to harvest hydrogen from waste plastic using a low-emissions method that could more than pay for itself.

The researchers converted mixed waste plastics into high-yield hydrogen gas and high-value graphene. 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."

"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. The scientists hope that this work will allow for the production of clean hydrogen from waste plastics, possibly solving both the major environmental challenge of plastic pollution and the greenhouse gas-intensive production of hydrogen by steam-methane reforming.