Artificial Photosynthesis Can Transform Industrial Wastes Into Eco-Friendly Plastics

Low concentrations of carbon dioxide can be reused as biodegradable plastic precursors through artificial photosynthesis. A research team led by Professor Yutaka Amao of Osaka Metropolitan University successfully demonstrated the use of artificial photosynthesis to synthesize poly-3-hydroxybutyrate, a biodegradable plastic, from waste acetone and low concentration carbon dioxide.

Using the energy equivalent to sunlight, the artificial photosynthesis system uses enzymes and rhodium catalysts to produce a biodegradable plastic precursor. Now, this process uses low concentration carbon dioxide (similar to waste gas) and waste acetone as raw materials for the first time.

The purpose of this study is to reuse waste acetone from permanent marker ink and carbon dioxide equivalent to exhaust gases from power plants and other industrial sources. After 24 hours, more than 60% of acetone was converted to 3-hydroxybutyric acid. The team's research results were published in Green Chemistry, emphasizing the practical application of artificial photosynthesis and their plan to further develop the technology to use waste materials more effectively.

Poly-3-hydroxybutyrate -- a biodegradable plastic -- is a waterproof polyester often used as packaging materials, which is made of 3-hydroxybutyrate as a precursor. In previous studies, the research team led by Professor Yutaka Amao of the Artificial Photosynthesis Research Center of Osaka Metropolitan University found that 3-hydroxybutyrate could be efficiently synthesized from carbon dioxide and acetone, but this was only proved when the concentration of carbon dioxide or sodium bicarbonate was high.

The new research aims to reuse the waste acetone and low concentration carbon dioxide from permanent marker ink - equivalent to the exhaust gas from power plants, chemical plants or steel plants. Acetone is a relatively inexpensive and reasonably harmless chemical, which is used in many different laboratory environments for reaction or as a cleaner to produce waste acetone. Acetone and carbon dioxide are used as raw materials to synthesize 3-hydroxybutyric acid through artificial photosynthesis, which is driven by light equivalent to sunlight. After 24 hours, more than 60% of acetone has been successfully converted to 3-hydroxybutyric acid.

"We are focusing on the use of carbon dioxide from coal-fired power plants and other sources to demonstrate the importance of the practical application of artificial photosynthesis," explained Professor Amao. "In the future, our goal is to further develop artificial photosynthesis technology, so that it can use acetone in liquid waste and laboratory waste gas as raw materials."

Their research results will be published in the journal Green Chemistry on March 1, 2023.