St Paul’s Convent School students invent artificial leaf to combat climate change


Three secondary school girls win the 2019 BASF Kids' Lab Experiment Challenge for creating a "leaf" out of algae that can absorb carbon dioxide

Joanne Ma |

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(From left) Rachel Ma, Zita Ng, and Katarina Shing were inspired to create an artificial leaf when they learned about algal blooms.

With climate change and multiple global environmental crises at hand, it’s hard not to think about what one can do to help. Three girls at St Paul’s Convent School had been constantly brainstorming and experimenting to find solutions until they came up with a brilliant idea.

The trio - Zita Ng Man-wai, Rachel Ma, and Katarina Shing Cheuk-yan - invented an “artificial leaf” that could help to reduce the impact of climate change. Because of this project, they won the BASF Kids’ Lab Experiment Challenge in November last year, a programme co-organised by leading chemical company BASF, and the Chinese University of Hong Kong (CUHK).

As huge as this project sounds, it comes from a tiny spark of inspiration. For more than a year, the group had been pondering ways to fix current global issues, specifically those related to the environment. In class, they were only told about the intensity of the problems, but they wanted more: they wanted to be involved in helping to mitigate them, too.

The artificial leaves made from algae can last up to six months.
Photo: Rachel Ma, Zita Ng and Katarina Shing

In their early secondary school years, the girls paid extra attention in their science and geography classes, hoping to equip themselves with a foundational knowledge that they could build their ideas upon.

“We’ve been passionate about science for a really long time and we’ve been sitting together in science class since Form 1. We were so eager to try different experiments in class, too,” Zita, 16, recalls.

One day, they learned about algal blooms, the rapid growth of algae and green plants in water due to climate change and industrialised agriculture, which leads to harmful and toxic effects to the organisms living in the habitat. A question bloomed in their minds: “If we have so much algae, why don’t we use it for something good? Like, perhaps, absorbing carbon dioxide?”

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After doing some research, they found that algae undergo photosynthesis just like any other green plant. After learning this, they sought to create an artificial leaf made from algae, one that wouldn’t take much time to produce or require much maintenance work.

“The cost of producing an artificial leaf, if we don’t consider any labour cost and if we assume that water is always available, is just HK$0.05. It’s a great invention in the sense that it’s accessible to all people – even little kids can produce it for fun,” says Zita.

Its production time is also shorter than the growth period of a normal leaf. It usually takes about one to two months for a real leaf to grow, but an artificial leaf doesn’t take longer than 45 minutes to be made. If the size of the mould in which the leaf is made is bigger, it can take up even more atmospheric carbon dioxide and ultimately prevent global warming from worsening.

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Another team member, Katarina, 15, says after losing so many trees in the Australian wildfires, the artificial leaf can also be able to substitute the real leaves for the time being, to absorb some of the carbon dioxide that’s being released.

“It normally lasts for three weeks and even after it dries, once you put it into water, it revives and can last up to six months,” Katarina adds.

The artificial leaf is made up of water, sodium alginate, calcium chloride and algae. To create one, you first leave the algae in water for 24 hours so it sinks and becomes a much more concentrated algae solution. Next, in a separate container, you stir sodium alginate with water for 15 minutes. Then you draw the sunken algae solution from the first beaker out and mix it with the sodium alginate solution. After mixing for 15 minutes, pour the jelly-like mixture into a leaf-shaped silicone mould, flatten it out, then add some calcium chloride to it and leave it to dry.

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According to the winning students, calcium chloride will react with sodium alginate and form a protective layer to prolong the lifespan of the artificial leaf.

Their experiment will be modified by BASF and CUHK chemistry experts and launched in BASF’s Kids’ Lab, a chemistry education programme designed for kids aged six to 12, in 2021.

“When we designed the experiment, our first priority was to employ some really common and easy concepts in science, like photosynthesis, also known as the survival process for leaves.” said Katarina.

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“But at the same time, we also wanted to touch on some global issues. The inspiration for the [artificial] leaf mainly came from algal blooms and global warming. Those are some major issues around the world right now.”

The team also wanted to highlight the civil responsibility that they think the younger generation needs to bear. “We want to let kids know that everyone can play a part in protecting the environment, even if you’re young and lack experience,” adds Katarina.

In a world that is full of problems, creativity plays a vital role in bringing about change and coming up with solutions. But the team is aware that that’s not all that is needed. They recall that when their idea first sparked, the next thing they did was research and learn more about the related concepts. Katarina concludes, “Knowledge and innovation come hand in hand, I think the key is to gather all of our innovative insights, and tie those with what we’ve already learned.”

Edited by Nicole Moraleda