NTU scientists find a way to convert plastic waste into low-carbon hydrogen

SINGAPORE — Scientists at Nanyang Technological University have found a way to convert plastic waste into low-carbon hydrogen, which is considered a cleaner fuel than natural gas.

The discovery, which could power vehicles and contribute to the electric grid in just three years, comes as the Republic seeks to adopt hydrogen as an alternative fuel, as it does not produce carbon dioxide (CO2) when it is burned.

To help Singapore reduce emissions from the electricity sector to net zero by 2050, the Energy Market Authority’s Energy 2050 Committee report had also suggested developing hydrogen-friendly infrastructure in clean burning for use as fuel.

The latest report from the United Nations’ Intergovernmental Panel on Climate Change (IPCC) has found that emissions of greenhouse gases – such as CO2 – must peak before 2025 and be reduced by 43% by by 2030 to limit the impacts of dangerous climate change.

This will allow the world to limit global warming to 1.5 degrees C above pre-industrial levels – a key target of the 2015 Paris Agreement. The world has already warmed by 1.1 degrees C.

Plastic waste, which contains contaminated food packaging, polystyrene and plastic bags, can be difficult to recycle, meaning it is currently incinerated or buried in landfills.

With 832 million kilograms of plastic waste generated each year in Singapore that cannot be recycled, NTU’s new method – a high-temperature chemical process known as pyrolysis – can convert waste into energy that can potentially power up to to 1,000 five-room apartments for one year.

Associate Professor Grzegorz Lisak of NTU’s Nanyang Water and Environment Research Institute (Newri), who led the project, told reporters during a virtual press conference on Wednesday (April 6) that the he other byproduct of the pyrolysis process would be a form of solid carbon, called carbon nanotubes.

Carbon nanotubes have a range of uses, including sensors, semiconductors and energy conversion devices, such as hydrogen fuel cells.

Andrei Veksha, principal researcher at Newri, said the gas mixture from the pyrolysis process had a concentration of around 78% hydrogen, 20-24% methane and a small amount of CO2.

This can be used to power gas turbines to generate electricity, or if a purer form of hydrogen is needed, the gases can be separated using existing technologies on the market, he added.

For example, hydrogen vehicles require very pure hydrogen at over 99.9%, as the presence of contaminants could impact fuel cell performance.

The remaining methane and CO2 gases can then be recycled and used to power the pyrolysis reactor. The chemical reaction will also leave behind a small amount of charcoal, which can be repurposed for other uses so it doesn’t end up in the Semakau landfill, Dr Veksha said.

Bryce K. Locke