A new method for converting plastic waste into hydrogen and carbon could help clean up oceans and seas and make plastics a fuel of the future.

That is according to Scientists from Nanyang Technological University (NTU) Singapore and the Ocean Purpose Project, a social enterprise based in the city-state. They say plastic waste can be converted into hydrogen by pyrolysis, a high temperature chemical process.

Unlike PET (polyethylene terephthalate), which is used for plastic soft drink bottles and can be recycled easily, plastic litter containing contaminated food packaging, styrofoam and plastic bags, is much more challenging to recycle.

The 832 million kilograms of unrecycled plastic waste a year generated in Singapore could be converted into enough energy to power up to 1,000 five-room apartments. Currently this kind of waste is incinerated or buried in landfills, leading to both water and ground pollution.

With 269 million kilograms of plastic waste currently floating in the oceans, the NTU team estimates that if converted into energy the waste could power an electric vehicle for 20 to 40 million kilometres – 500 to 1,000 times the Earth’s circumference.

Hydrogen conversion

Using pyrolysis, plastic litter can be converted into two main products: hydrogen, and a form of solid carbon called carbon nanotubes, used in industry. Hydrogen is useful for generating electricity and powering fuel cells like those found in electric vehicles, with clean water as its only by-product.

To further refine the new conversion method and to assess whether it can be commercialised, the research team is testing it on the NTU Smart Campus to treat local plastic waste. The trial is being carried out in partnership with Bluefield Renewable Energy, a local environmental firm that specialises in mobile waste to resources technologies

The project will also explore the potential of other emerging technologies for decentralised waste management. The conversion of challenging waste streams into energy and valuable resources, such as syngas, biochar, activated carbon and carbon nanotubes will be investigated.

Led by associate professor Grzegorz Lisak from NTU’s Nanyang Environment and Water Research Institute (NEWRI), the research project used marine litter collected from local waters in collaboration with the Ocean Purpose Project, a non-governmental organisation and social enterprise based in Singapore.

Trash to treasure

“As part of NTU’s sustainability drive, in developing new ways to turn trash to treasure, we are looking to convert waste plastics that cannot be recycled into high-value chemicals and resources, such as hydrogen fuel, synthetic fuel that could replace petrol, and carbon nanotubes used for many industrial applications,” explained Lisak.

Last November, NEWRI researchers participated in Race For Oceans Singapore, a kayak race organised by the Ocean Purpose Project, to collect plastic waste along the shores of Singapore. The purpose was two-fold – to clean up marine litter through sports as community mobilisation and to use these litter as research materials for developing an efficient plastic waste-to-hydrogen process.

Mathilda D’silva, founder and chief executive of Ocean Purpose Project, said, “The cutting-edge research, innovation and dynamism of the NTU NEWRI team is a dream collaboration for NGOs like us in ocean conservation, who have to move beyond awareness campaigns and beach clean-ups towards completely disrupting our ideas of how plastic waste should be handled. We are proud as plastic-to-resources influencers to promote our Singapore-based research that will forge a new future for plastic recovery, potentially cleaning thousands of coastlines in Asia.”

Craig Gavin, chief technology officer at Bluefield Renewable Energy, said: “Collaborating with NTU NEWRI has allowed us to utilise these environmentally unfriendly plastic waste streams as a feedstock and converting them into valuable resources.”

The research team says the solid carbon from their new conversion process is much easier to store as compared to gaseous CO₂ emissions from plastic waste incineration. Furthermore, the solid carbon can be easily sold as a manufacturing feedstock for speciality chemicals or biofuels.

For instance, it is a greener source of carbon for making carbon nanotubes, which is useful for many applications such as for batteries and composite manufacturing, says NEWRI Senior Research FellowDr Andrei Veksha, the co-inventor of the process who is piloting the technology.

Plastic waste-to-hydrogen is a two-stage process: plastic waste is first decomposed upon heating into gases that contain low concentrations of hydrogen molecules. During the second stage, when the gases enter a reactor filled with a catalyst, the technology enables the release of hydrogen fuel and the formation of carbon nanotubes.

If the initiative is successful, it will help Singapore reduce the amount of total waste disposed and prolong the lifespan of Singapore’s only landfill, Semakau Landfill, which is estimated to run out of space by 2035.

The multimillion-dollar research joint project is supported by the Industry Alignment Fund-Industry Collaboration Projects (IAF-ICP) administered by Singapore’s Agency for Science, Technology & Research (ASTAR). It aims to develop feasible solutions to economically scale-up the conversion of waste plastics to hydrogen over the next three years.