Since their discovery in the early 20th century, polymeric materials have revolutionized many aspects of our lives. Perhaps the most recognizable polymers in our daily lives are plastics.

Despite their enormous value, we produce more plastic than we recycle, and this is becoming a major environmental challenge. The figures are staggering: Just 9 percent of the global supply of plastic is recycled. Most plastic produced is incinerated or placed in landfills, leading to pollution. A significant amount of plastic waste is also found in the seas, creating not just an eyesore but damage to aquatic life and marine ecosystems.

At Khalifa University, Sharmarke Mohamed and his team at the Advanced Materials Chemistry Center (AMCC) are developing a new method for recycling post-consumer plastic waste that uses a combination of mechanical force (as part of mechanochemistry), light and catalysts.

“Despite the enormous environmental challenge posed by plastic waste, we felt a sense of duty to develop these new mechanochemical tools. Most researchers around the world are exploring mechanical force as a means to build new chemicals. In other words, building complexity from simple structures. We decided to use the same principles and use mechanical force as well as light and catalysts to break down complex polymer waste materials into smaller building blocks that can then either be recycled or upcycled,” he says.

“Solar energy is responsible for the photodegradation of plastics in the environment, particularly in the UV region of the electromagnetic spectrum. We also know that some biological catalysts (e.g. enzymes) are adapted to using organic macromolecules such as plastics as fuel sources. So in essence, we are learning from nature as we try to develop a lab-scale protocol that uses these tried-and-tested methods for turning plastic waste into high-value chemicals,” Mohamed says.

“As the UAE declares 2023 to be the Year of Sustainability, our research group is very much leading this effort in a challenging area. But we are motivated by solving the environmental challenges posed by plastic waste,” Mohamed says.

About 380 million metric tons of plastic are produced each year. Of that, only about 9 percent is recycled, Mohamed tells the KUST Review. Some plastics are treated with harsh chemicals, like acid. But most plastic is incinerated, he says.

“But the problem (with incineration) is that it releases carbon dioxide and adds to the global carbon footprint. The other problem is that if you burn the plastic you can’t reuse it. Our group is trying to take the end-user plastic and come up with new low-cost mechanical methods that are able to break down these polymers into their constituent parts.”

Those constituent parts might then be reused to make new plastic products or chemicals for other uses.

Mohamed’s team is working on a three-year project to investigate a three-part process for recycling plastics. This research is supported by AMCC and funded by ASPIRE, the technology program management pillar of Abu Dhabi’s Advanced Technology Research Council (ATRC), via the ASPIRE Award for Research Excellence.

The value of this technology is that it uses no corrosive or harmful chemicals, which is important as it makes the entire process much more environmentally friendly than incineration or land-filling the plastic waste.

The next step is to examine the influence of light on the process, followed by experiments with inorganic catalysts (i.e. metal salts) or enzymes to break down the plastics.

“Once we understand each of these processes on their own, we can see how they can be stitched up together to create what we refer to as a photolytic and mechanoenzymatic degradation (PMED) protocol. We envisage the PMED process will be implemented serially as part of a batch process, much like a conveyor belt in a factory. Our long-term goal is to take post-consumer plastic waste and to efficiently produce the chemical building blocks of the plastic waste via our PMED process.”

Different forms of plastic break down in different ways under mechanical force, complicating the process, Mohamed says. But he says the initial work is promising.

Zeinab Mohamed Saeed, a Ph.D. candidate working on the project, says she’s excited by the non-conventional approach to a long-standing problem.

“The field of polymer degradation was there for decades,” she says. “People have been trying to come up with different ways to tackle the issue using their expertise, and now we are trying to think outside the box and look at the problem from a non-conventional perspective using a mechanocatalytic approach. I find this research challenging but exciting, and can’t wait to see what kind of results we will end up with.”

Among the challenges, however, is creating vessels that can hold the material but also allow in light of a certain wavelength. And the enzymes known to break down plastics are expensive.

The hope, however, is to scale up the technology to levels required by industry. That’s still some time off, however.

“Now we can do up to a gram or two. This is fine for feasibility and patenting,” Mohamed says.

The Advanced Materials Chemistry Center (AMCC) was formed in 2022 and combines expertise from different disciplines to tackle major environmental problems. Its methods for treating plastic waste “align with the UAE’s ambitions to transition to a green circular economy and achieve its net-zero targets” Mohamed says.