Researchers have succeeded in extracting hydrogen from plastic waste. A key advantage here is that during this production process, graphene is created as a by-product. This allows the method to "more than pay for itself", according to researchers at US Rice University.
Hydrogen is a promising energy source. It can be used for various purposes, ranging from powering passenger cars and truck traffic to industrial use as an alternative to natural gas.
Polluting and costly
A major challenge, however, is the production of hydrogen, something that normally consumes a lot of energy. As a result, production can generate relatively large CO2 emissions when using fossil fuels as energy sources. By 2022, for instance, almost 100 million tonnes of hydrogen was produced worldwide using fossil fuels. This generated about 12 tonnes of CO2 emissions per tonne of hydrogen produced.
Producing hydrogen is also relatively expensive. For instance, the production of green hydrogen - which uses renewable energy to separate water is oxygen and hydrogen - costs around $5 for about 900 grams.
Converting mixed plastic waste into hydrogen
The researchers expect that their invention could provide a solution to this problem. They have succeeded in converting plastic waste into hydrogen gas. The method offers important advantages. For instance, separating plastic types and washing plastic waste is not necessary, something that is the case with recycling.
Another major advantage is that the production process creates graphene as a by-product. Graphene is over two hundred times stronger than steel, flexible, very thin and transparent. In addition, the material is an excellent thermal and electrical conductor. A major application of graphene is electronics. However, think also of water purification and medicine.
Free production is possible
"In this work, we have turned plastic waste - including mixed plastic waste that does not need to be sorted by type or washed - into a high-yield hydrogen gas with valuable graphene," explains Kevin Wyss, a Rice University alumnus and lead author of the study. "If the produced graphene is sold for just 5% of its current market value - a 95% discount! - clean hydrogen can be produced for free."
"The main form of hydrogen in use today is 'grey' hydrogen. This is produced via steam reforming, a method that generates a lot of CO2," said James Tour, professor of chemistry and professor of materials science and nanotechnology at Rice University. "The demand for hydrogen is expected to skyrocket in the coming decades, so if we are serious about achieving net zero emissions by 2050, we cannot keep making it the way we have done so far."
Heating to high temperature in a short time
In the study, plastic waste was heated to about 2,827 degrees Celsius over a short period of time. This used a method called 'flash Joule heating', developed by Rice University. For this, the researchers combine ground plastic waste with a coke additive, which they place between electrodes in a tube. They then apply a high voltage. This creates intense heat in a short time, which can reach 2,760 degrees Celsius. The high temperature causes the hydrogen present in the plastic material to evaporate, leaving graphene behind.
The method was initially developed for graphene production. However, experiments showed the release of several gases, which the researchers investigated further. One of these substances turned out to be hydrogen. So further research in this area now shows that there are great opportunities here.
125 million euro subsidy for hydrogen switchover
The discovery of this method comes shortly after the government announced it would make 125 million euros available to support the transition to hydrogen as a fuel for lorries and (delivery) vans. The funding is intended to encourage businesses to make the switch to hydrogen. To do so, they must partner with filling station operators; every plan must include both a hydrogen filling station and a sufficient number of commercial vehicles to make the station viable.
In addition, the Netherlands is working on large-scale offshore water production in the wind energy area north of the Wadden Islands. The park should be operational by 2031 and offer some 500 megawatts of electrolysis capacity.
Converting waste into green hydrogen
Rice University is not, incidentally, the only organisation working on extracting green hydrogen from waste. Earlier this year, the German company RWE received a European grant of 108 million euros for converting residual waste into hydrogen. This specifically concerns non-recyclable solid household waste, which is currently still being incinerated or sent to landfill.
More information is available here.
Author: Wouter Hoeffnagel
Photo: Roman via Pixabay
