Can we “confront the grim reality” of plastic waste? | Inés and Kanishka
- hederahelixscience
- Sep 14, 2021
- 2 min read
Why convert plastic into clean hydrogen?
Chemists have used microwaves to convert plastic bags, milk bottles and other supermarket packaging into a clean source of hydrogen. Hydrogen can store and deliver usable energy but it doesn’t typically exist by itself in nature and has to be produced from compounds that contain it.
Hydrogen is an attractive fuel option for transportation and electricity generation applications. It can be used in cars, in houses, for portable power and in many more applications. Hydrogen has the ability to reduce greenhouse gas emissions in many applications like transportation and heat and power systems.
Plastic waste can already be converted to hydrogen using other methods, and commercial facilities are being developed to transform the plastic. However, a new approach holds the promise of being quicker and less energy-intensive.
Existing approaches
Most existing approaches involve first using very high temperatures of more than 750°C to decompose plastic into syngas, a mixture of hydrogen and carbon monoxide, and then using a second step to separate out the hydrogen.
What is the process?
By breaking the plastic into small pieces with a kitchen blender and mixing it with a catalyst of iron oxide and aluminium oxide, then blasting a microwave generator at 1000 watts, the catalyst creates hot spots in the plastic and strips out the hydrogen – recovering 97 per cent of the gas in the plastic within seconds.
The single-step approach has the advantage of just heating the catalyst, not all of the plastic, resulting in less energy use, as the plastic does not absorb microwaves.
Larger experiments are currently being planned.
Currently most hydrogen is produced from fossil fuels, specifically natural gas. Renewable sources such as biomass or geothermal are also currently used to produce hydrogen. In the longer term biomass can be used more directly to generate hydrogen as new technology is produced.
There are also different production pathways where a lot of hydrogen is also produced. The most common production pathways are a thermal process and electrolysis. The thermal process often involves a high temperature process in which steam reacts with a hydrocarbon fuel to produce hydrogen. Around 95% of all hydrogen is produced by this process. In the electrolytic process, water can be separated into oxygen and hydrogen through a process called electrolysis.
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