Could tiny water droplets hold the key to dissolving the global plastic waste crisis?
International team of scientists develop catalyst-free plastic recycling process with just water and oxygen
A new way of converting stubborn plastic waste into high-value chemicals using only water and oxygen, has been developed by an international team of scientists.
The researchers from Zhejiang University, in collaboration with Cardiff University, the University of Tokyo and others, successfully transformed a wide range of everyday plastic waste including polyethylene, polypropylene, and even rubber tyres into value-added organic acids.
These acids are essential chemical building blocks widely used in medicines, food additives, and the manufacturing of biodegradable materials.
Recycling processes of this kind are usually kick-started by expensive and sometimes toxic catalytic technology, according to the team.
Their study, published in the journal Nature, instead offers a simple, economically viable and catalyst-free recycling strategy to one of the world's most pressing environmental challenges.
Professor Yong Wang, the study’s lead author from the Zhejiang Provincial Key Laboratory of Low-carbon Synthesis of High-value Chemicals at Zhejiang University, said: “By eliminating the need for expensive or toxic catalysts entirely, we have removed one of the major economic and environmental barriers to the industrial adoption of chemical plastic recycling.”
The team’s innovation is powered by tiny water droplets.
By simply melting and stirring the plastic in water, the polymer disperses into microscopic droplets.
This process creates a dynamic water-oil interface where highly reactive hydroxyl radicals are generated spontaneously.
These natural radicals act as “chemical scissors,” neatly cleaving the tough bonds of the polymer chain.
Using polyethylene as a model, the team achieved near-complete plastic conversion with a 69% yield of short-chain diacids under mild conditions, leaving no microplastic residues behind.
Professor Graham Hutchings, one of the study’s co-authors and Regius Professor of Chemistry at Cardiff University’s Cardiff Catalysis Institute, added: “We are awash with plastic waste, and we need viable solutions for its effective recycle. Our discovery shows the way, demonstrating that water and oxygen alone – under the right microdroplet conditions – are powerful enough to drive the selective oxidation of some of the most chemically inert and durable materials on Earth.”
While the unique chemical properties of microdroplet interfaces have fascinated scientists for years, this study marks the first time the phenomenon has been harnessed at a practically relevant scale.
The researchers successfully scaled up the process to a 300g batch in the lab, demonstrating its commercial viability.
Crucially, the method is robust enough to tolerate commercial additives and mixed waste streams that would typically poison and deactivate conventional catalysts. Furthermore, it works perfectly using both tap water and seawater.
The paper, ‘Catalyst-free, microdroplet-mediated waste plastic conversion to diacids’, is published in Nature.
ENDS
International team of scientists develop catalyst-free plastic recycling process with just water and oxygen
A new way of converting stubborn plastic waste into high-value chemicals using only water and oxygen, has been developed by an international team of scientists.
The researchers from Zhejiang University, in collaboration with Cardiff University, the University of Tokyo and others, successfully transformed a wide range of everyday plastic waste including polyethylene, polypropylene, and even rubber tyres into value-added organic acids.
These acids are essential chemical building blocks widely used in medicines, food additives, and the manufacturing of biodegradable materials.
Recycling processes of this kind are usually kick-started by expensive and sometimes toxic catalytic technology, according to the team.
Their study, published in the journal Nature, instead offers a simple, economically viable and catalyst-free recycling strategy to one of the world's most pressing environmental challenges.
Professor Yong Wang, the study’s lead author from the Zhejiang Provincial Key Laboratory of Low-carbon Synthesis of High-value Chemicals at Zhejiang University, said: “By eliminating the need for expensive or toxic catalysts entirely, we have removed one of the major economic and environmental barriers to the industrial adoption of chemical plastic recycling.”
The team’s innovation is powered by tiny water droplets.
By simply melting and stirring the plastic in water, the polymer disperses into microscopic droplets.
This process creates a dynamic water-oil interface where highly reactive hydroxyl radicals are generated spontaneously.
These natural radicals act as “chemical scissors,” neatly cleaving the tough bonds of the polymer chain.
Using polyethylene as a model, the team achieved near-complete plastic conversion with a 69% yield of short-chain diacids under mild conditions, leaving no microplastic residues behind.
Professor Graham Hutchings, one of the study’s co-authors and Regius Professor of Chemistry at Cardiff University’s Cardiff Catalysis Institute, added: “We are awash with plastic waste, and we need viable solutions for its effective recycle. Our discovery shows the way, demonstrating that water and oxygen alone – under the right microdroplet conditions – are powerful enough to drive the selective oxidation of some of the most chemically inert and durable materials on Earth.”
While the unique chemical properties of microdroplet interfaces have fascinated scientists for years, this study marks the first time the phenomenon has been harnessed at a practically relevant scale.
The researchers successfully scaled up the process to a 300g batch in the lab, demonstrating its commercial viability.
Crucially, the method is robust enough to tolerate commercial additives and mixed waste streams that would typically poison and deactivate conventional catalysts. Furthermore, it works perfectly using both tap water and seawater.
The paper, ‘Catalyst-free, microdroplet-mediated waste plastic conversion to diacids’, is published in Nature.
ENDS
Journal
Nature
Nature
DOI
Method of Research
Experimental study
Experimental study
Subject of Research
Not applicable
Not applicable
Article Title
Catalyst-free, microdroplet-mediated waste plastic conversion to diacids
Catalyst-free, microdroplet-mediated waste plastic conversion to diacids
Article Publication Date
15-Jul-2026
15-Jul-2026
Low carbon dioxide levels improve microbial production of biodegradable plastic
Nonflammable gas mixtures improve carbon dioxide conversion efficiency for production of biodegradable plastic
Institute of Science Tokyo
image:
Researchers found that low CO₂ levels under non-combustible gas conditions can increase P(3HB) production by improving carbon utilization efficiency.
view moreCredit: Institute of Science Tokyo (Science Tokyo), Japan
In an innovative gas fermentation process, reducing the concentration of carbon dioxide was found to significantly improve microbial production of the biodegradable plastic, poly[(R)-3-hydroxybutyrate]. Researchers found that hydrogen-oxidizing bacteria grown under safe, nonflammable gas conditions enable more efficient production of biodegradable plastic at lower CO2 levels. The study provides a promising strategy for sustainable carbon recycling and efficient CO2 utilization.
As the efforts to reduce carbon dioxide (CO2) emissions accelerate worldwide, scientists are exploring ways to transform this abundant greenhouse gas into useful products. One of these approaches is microbial CO2 conversion, which uses naturally occurring microorganisms to convert CO2 into sustainable materials. Particularly, Ralstonia eutropha (a hydrogen-oxidizing bacterium) is widely used in this process, and uses hydrogen, oxygen, and CO2 for synthesis of biodegradable plastics such as poly[(R)-3-hydroxybutyrate] (P(3HB)).
Conventional gas fermentation systems often require high hydrogen concentrations in flammable range, which affects the safety of the process. To address this, a research team from Institute of Science Tokyo (Science Tokyo), Japan, had previously developed a noncombustible gas culture system. Now, the group used the noncombustible system and investigated how adjusting the concentration of CO2 could improve the production of P(3HB) under safe operating conditions. The study was led by Assistant Professor Yuki Miyahara from the Department of Materials Science and Engineering, Science Tokyo, in collaboration with graduate student Chih-Ting Wang, Postdoctoral Researcher Ramamoorthi M Sivashankari, and Professor Takeharu Tsuge, all from Science Tokyo. The findings were made available online on April 17, 2026, and published in Volume 14, Issue 16 of the journal ACS Sustainable Chemistry & Engineering on April 27, 2026.
“We observed that reducing CO2 concentration resulted in higher production of P(3HB),” explains Miyahara.
On the contrary to the conventional expectations, the researchers discovered that lowering the supply of CO2 to approximately 1.4% by volume, significantly increased the accumulation of P(3HB) inside the cells. Moreover, the bacteria not only produced more plastic but also converted the CO2 more efficiently than the cultures grown under higher CO₂ concentrations.
To further understand why low CO₂ concentrations improved polymer production, the team investigated the role of carbonic anhydrase (Can), which is an enzyme that rapidly converts CO2 into bicarbonate. Since this reaction plays an important role in supplying inorganic carbon for cellular metabolism, the researchers tested whether increasing the enzyme’s activity could enhance the production of P(3HB). The results revealed that increasing Can expression boosted the accumulation of P(3HB), but only under low CO₂ conditions. This suggests that efficient carbon processing within the cells is very important when external CO2 is limited. The increased expression of Can enzyme ensured ample supply of inorganic carbon, allowing the cells to produce larger amounts of biodegradable plastic.
“The combined effect of low CO2 and enhanced Can activity reveals an effective strategy for improving microbial carbon utilization, making it safer and more efficient,” comments Miyahara.
According to the authors, low CO₂ availability triggers adaptive cellular responses within the bacterial cells, which improve the carbon utilization efficiency. Therefore, instead of limiting the growth, moderate CO2 scarcity encourages the cells to use available carbon more effectively, which results in greater polymer accumulation. However, under higher CO₂ concentrations, these adaptive responses become less pronounced as carbon is already readily available.
Overall, the study inspires the development of industrial processes that are capable of converting low-concentration CO2 sources, such as exhaust gases, into biodegradable plastics. By combining safer gas handling along with improved carbon conversion, the approach offers a promising path for sustainable carbon recycling and reducing the emission of greenhouse gases, while also producing eco-friendly materials.
In the future, the researchers plan to further improve the process and extend this strategy to other microorganisms and products. These advances could accelerate the development of new processes that could transform waste carbon into a wide range of renewable materials, supporting the transition towards a circular carbon economy.
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About Institute of Science Tokyo (Science Tokyo)
Institute of Science Tokyo (Science Tokyo) was established on October 1, 2024, following the merger between Tokyo Medical and Dental University (TMDU) and Tokyo Institute of Technology (Tokyo Tech), with the mission of “Advancing science and human wellbeing to create value for and with society.”
Reference
DOI: https://doi.org/10.1021/acssuschemeng.6c00126
Journal
ACS Sustainable Chemistry & Engineering
Method of Research
Experimental study
Subject of Research
Cells
Article Title
Impact of Low CO2 Concentration on Autotrophic Production of Poly[(R)‑3-hydroxybutyrate] by Ralstonia eutropha H16 and Synergistic Effect of Carbonic Anhydrase
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