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Turning plastic pollution into green energy


Turning plastic pollution into green energy

Chemical Engineering lecturer Dr Anh Phan has developed a pioneering technique to produce clean fuels and materials from plastic. She tells us more about her research and its potential to revolutionise how we deal with plastic waste.

Today 31% of plastic waste in the EU ends up in landfill, having a devastating effect on our ecosystems and oceans.

Even with ambitious recycling targets in place – the UK aims to recycle 50% of all household waste by 2020 – we’re still a long way from resolving the issue.

But Dr Anh Phan, a lecturer in Chemical Engineering at Newcastle University’s School of Engineering, may have a solution.

She is currently leading a pioneering research project to convert waste plastic into green energy and useful chemicals and materials through a process known as cold plasma pyrolysis.

Anh first started researching energy recovery from the waste left behind after recycling in 2004 during her PhD, when she discovered that plastic made up about 13% of municipal waste streams.

After her appointment at Newcastle University in September 2013, she was determined to continue her investigation.

Plastics are actually valuable waste materials as they contain carbon and hydrogen and have a similar energy content to fuels such as diesel,” she explains.

However, rather than focusing solely on the potential to generate fuel from this waste plastic, Anh decided to go one step further and try to recover other higher-value materials.

An equation showing a plastic bottle and cold plasma hydrolysis producing chemicals which are used to produce energy.

A new approach

This is where cold plasma pyrolysis came in. Pyrolysis is a method of thermal decomposition in an environment with limited oxygen at temperatures between 400-650°C.

The process can be used to generate electricity and fuels, but when cold plasma is added to the equation it can convert waste plastics into hydrogen, methane and ethylene.

Hydrogen and methane can be used as clean fuels as they produce minimal amounts of soot and carbon dioxide, while ethylene is the building block of most plastics.

“Instead of wasting plastics, cold plasma pyrolysis can recover valuable materials, which can be used to produce other plastic products in turn,” explains Anh.

Her study, using plastic bags, milk and bleach bottles from a local recycling facility in Newcastle found that 55 times more ethylene can be recovered from the most widely used, everyday plastic (high-density polyethylene, or HDPE) with cold plasma.

Better still, 24% of the plastic used in the experiment was converted from HDPE into valuable products.

“Essentially what I’m trying to do is to take the plastic pollution, recover the ethylene and then feed it back into the beginning of the plastic manufacturing process so we can stop relying on fossil fuels,” she says.

What I’m trying to do is to take the plastic pollution, recover the ethylene and then feed it back into the beginning of the plastic manufacturing process so we can stop relying on fossil fuels.

Dr Anh Phan

Looking beyond recycling

Anh is hoping to use her findings to develop a circular, low-carbon economy – one that offers a more viable long-term solution to dealing with discarded plastic other than by simply recycling it.

“You cannot recycle for ever,” she warns. “After so many times, the products turn to waste and then how do you deal with that?”

While it can take hundreds of years for certain plastics to completely degrade, cold plasma pyrolysis offers a quick alternative.

It produces highly energetic electrons that can break down the chemical bonds in plastic waste in a matter of seconds – meaning the process has the potential to be affordable too.

What’s more, Anh adds that the electricity used to generate cold plasma can be sourced from renewables, while the chemical products derived from the process are then stored as energy for further down the line.

She believes it will take another two or three years for the process to be scaled up for use in the polymer industry, but she needs more resources to do so and has applied for funding to help put cold plasma technology into action.

“People in the industry keep asking me if it’s ready,” she says. “There’s definitely a gap in the market for such a solution.”

And with an estimated eight million tonnes of plastic waste currently ending up in our oceans each year, the potential to transform this damaging waste product into something – in Anh’s words – “clean and useful” couldn’t come soon enough.