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One-on-One With NTU Scientist Soo Han Sen — Turning Plastics Into Food Preservatives

As someone acutely aware of the global problem we have with plastic, I often try my best not to contribute to the Great Pacific Garbage Patch by forgoing disposable plastic as much as possible. Other than reducing our usage, we should also recycle when appropriate and replace our disposables with long-term sustainable alternatives.

This journey of sustainability led me to wonder what else could be done about the plastic problem other than using sustainable alternatives. I decided to do some research, which brought me to Associate Professor Soo Han Sen and his team’s research on turning non-biodegradable plastic into useful chemicals using sunlight.

Essentially, a catalyst is a substance that speeds up a chemical reaction, add the word photo in front of it and that means that the reaction is sped up with the use of a light source. The photocatalyst, with the help of sunlight, will break down non-PET plastics into formic acid, an acid used in food preservatives and cleaning products.

This process is absolutely revolutionary as it’s the first of its kind worldwide and can potentially lessen our plastic pollution on a grand scale. My fascination led me to contact Associate Professor Soo to have a better understanding of his motivations and the scientific process of this method of turning plastics into formic acid.

Leo Goh: How do you describe what you do to someone who isn’t from the science or academic community?

Han Sen: In our team, what we’re interested in is finding ways to develop technologies that can convert sunlight to turn things we consider as waste into useful chemicals. Like fuels for example, so a few of the things we’re interested in doing is take greenhouse gases like carbon dioxide and turn it into fuels or take biomass or plastics and turn it into fuels or chemical feedstocks that can also be used to make other things.

L: Of all the man-made materials, why plastic? And what triggered this two-year-long search for the technique of dissolving plastics?

HS: Initially, we wanted to tackle the issue of biomass due to the bad haze in 2013 and examine what contributed to the worsening situation. We looked at clearing rainforests in a way that allows the wood chopped down to be made into useful products. The goal was to find a way to incentivise farmers to not burn down the wood waste and try to turn that into something useful instead.

This led us to develop a photocatalyst to try to break down woody materials into something useful. We then patented our work and was able to turn some smaller parts of the wood into things like vanillin, which is what you use for vanilla flavour.

Along the way, we had to apply for research grants. So in 2017, we applied for an AStar grant in advance manufacturing and engineering. During the process, the review panellist asked me to think of other ways we can use this technology. In our original work on wood waste, how our catalyst works is that it latches on to the trash and breaks the carbon-carbon bond in the wood waste selectively.

Since it breaks carbon-carbon bonds, I pondered on what else we could use it for—what other things have carbon-carbon bonds? The first thing that came to my mind was plastics that can be found in the ocean. That’s how we considered plastic. It took us a while because we had to find the optimal conditions to break it down, but we eventually succeeded.

L: Would you say your childhood and education led you to the motivations you have today?

HS: I would say that my education did, probably not so much my childhood. My childhood was somewhat random.

I was brought up mostly by a babysitter and my grandparents, so there was nothing particularly inspiring about my childhood. But I did have the privilege of going to the right schools in Singapore and was surrounded by really motivated classmates. This motivated me to try to work harder in academics. But I soon realised that having individual achievements don’t mean much to the rest of the world. That’s what got me interested in trying to work on areas which I think can be impactful.

L: Given your education in the United States (US), what are the differences in recycling and climate change attitudes between the US and Singapore?

HS: It’s very different. In the US, given the polarised society, some people are very enthusiastic and passionate about recycling and the environment. Still, then there’s the other end of the extreme, where people don’t believe in any of it.

In Singapore, we are more moderate. But the downside is that we are a bit more apathetic. There isn’t as much interest or motivation in these issues. I think it’s mainly because we’ve been trained to believe that Singapore is a small country and we can’t contribute very much, which is not justified.

You see, technology is not something that requires a large population size—technologies and ideas come from individuals. Of course, there needs to be some critical mass, but I think in Singapore we have sufficient critical mass to bring technologies forward.

“In Singapore, we are more moderate. But the downside is that we are a bit more apathetic”

L: Say your experiment does reach a point of commercial viability, how big of an impact do you think your research will make? Do you see plastic manufactures taking advantage of your experiment?

HS: Assuming that we can reach commercial viability, I would say that we still need a lot of time and hard work to move anywhere near that stage. If it can get to that stage then, yes, it would be very impactful. But getting to that step is not easy.

Since these news articles came out, surprisingly, most of the people who contacted me are plastic manufacturers and not those from the recycling industry. There is a considerable impetus for plastics manufacturers to do something about the problem.

Increasing government regulation and consumer pressure motivates them to turn their products into things that are more eco-friendly and biodegradable. They were excited to know that we potentially have a way to do that.

L: Do you think our government is doing enough?

HS: We are on the right track but are still relatively conservative and are always waiting for others to take the lead. I was a little surprised that we signed on to the Paris Agreement because we never ratified the previous agreement in 2009.

The argument given by the Minister of Environment, was “because the big countries like China, US and India, did not sign on to this, what’s the point for us to sign on?” Which led the government to wait for others to take the lead before doing the right thing. But we’ve introduced the carbon tax, that’s why I believe we’re on the right track.

But the price that we’re putting on the carbon is much lower than acceptable. I think we’re not as aggressive as we can be due to our pro-business environment, thus this tax feels more like a light rap on the hand to motivate companies to act.

L: When you look at the current state of climate change and environmental awareness in the world today, what is one thing that gives you hope?

HS: It took me a while to think of that because it’s rather depressing. After much thought, maybe there is still hope. I would say that the Chinese government gives me hope.

Just by statistics alone, the world’s most significant contributors to greenhouse gases and consumption will probably be China and India in the next 5-10 years. Unlike the US, the Chinese government has fairly and consistently acknowledged that climate change is a real problem, and have been a lot more proactive in doing something about it.

“Just by statistics alone, the world’s most significant contributors to greenhouse gases and consumption will probably be China and India in the next 5-10 years.”

Last year, the Americans pulled themselves out of the Paris Agreement, but the Chinese have not. With the size of their economy, as long as they continue to try to support this effort, there is hope that we can slow down or reverse the process. Because without them, it’s virtually impossible.

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