Breaking down plastics

Image of microbial cells and biopolymer granules (bar 500 nm).
Image of microbial cells and biopolymer granules (bar 500 nm).
In a world where plastic bags and plastic bottles are consumed in the millions annually, the fight to reduce such waste seems a daunting battle. Consumers are doing their part by becoming more socially aware about these environmental issues and making a conscientious effort to buy products and technology that are sustainable and eco-friendly. In response, Jian Yu, an associate researcher with UH Mānoa’s Hawaii Natural Energy Institute, and his team, are creating new technology to meet the increasing demands in the marketplace.

Yu’s research has led to the creation of thermoplastic materials from renewable feedstocks, such as agricultural wastes and food processing byproducts. The bio-based plastics, called PHA (polyhydroxyalkonoate) bioplastics, are completely biodegradable and biocompatible, whereas their petroleum-based counterparts are not. Petroleum-based plastics are not biodegradable and eventually find their way to the open seas, killing hundreds of thousands of birds, fish and other marine animals every year. “Compared to the conventional plastics, bioplastics consume less fossil energy and release much less greenhouse gases as indicated by numerous life-cycle analysis,” said Yu.

Biodegradable plastics were introduced about 20 years ago when a biochemical company had a successful pilot production of the biopolyesters from glucose and propionic acid. The bioplastics were used to make various goods such as shampoo bottles, credit cards, syringes and containers.  While its ecofriendly properties were groundbreaking at the time, the high costs associated with producing the product prevented it from being widely marketed.

A chemical/biochemical engineer by training, Yu was excited by the research that could lead to new technologies to bring down the high cost of production.  “I first investigated if cheap but complicated raw materials such as food scraps could be used for biopolymer production by microbial organisms,” said Yu.

His research was successful and gained recognition from his peers, including a published paper in Environmental Science and Technology in 2002. “Now, the technology has been used for other cheap feedstocks, such as sugar molasses, a residue from sugar manufacturers, and crude glycerol waste discharged from biodiesel production,” shared Yu. “We are able to achieve a very high special productivity rate for commercial production.”

Yu’s PHA bioplastics technology consists of three parts, including (1) pretreatment of feedstocks into suitable substrates for a special type of microbial organism, (2) high cell density fermentation for biosynthesis of biopolyesters, and (3) solvent-free recovery and purification of biopolyesters to make the final product of bioplastics.

At the end of fermentation process, their cells can accumulate 60-70 percent biopolyester of their mass.  In order to purify the biopolymer for bioplastics, the rest of the 30-40 percent of residual cell mass must be removed in a cost effective way. One conventional technology relies on organic solvent extraction, which is not only expensive, but also environmentally unfriendly. “We developed a new technology in which no organic solvent is needed, and at the same time, the cell debris generated from recovery process can be reused in biopolymer production,” added Yu.

The technology shows real potential. He already has a commercialization plan in place and has filed two patents on the technology, which is being used in a pilot plant in Europe. “The pilot plant has been built up according to our specifications and has been running successfully, providing data for scaling up to a commercial production,” said Yu. The company that operates the plant has invested $2 million to establish a central testing center in Honolulu, Hawaii, that will provide characterization and analysis service to its global manufacturing and markets.

In terms of waste reduction, Hawaii will see the benefits of Yu’s research. With large quantities of biomass generated by the state every year, the “green garbage” can be used as renewable feedstocks to make the bioplastics using their biorefining technologies.  “We have no oil resource for a petrochemical industry, but it is highly possible to have a manufacturing industry based on its plentiful renewable resources,” added Yu.

Although the price to make bioplastics is still higher than those of oil-based plastics, Yu believes his research will lead to technologies that can reduce the high production cost and bring the bioplastics to the consumers at a competitive price, in hopes of averting a mass environmental disaster. “The product exhibits good properties and can compete with similar products if the production cost can be reduced to a level widely accepted in the markets,” said Yu. Until then, consumers can count on more green products to hit the marketplace for years to come.

For more information, visit the Hawaii Natural Energy Institute website at

For more about the exciting research now being conducted at the University of Hawaiʻi at Mānoa read Inspiration to Innovation – the Chancellorʻs Report 2011-2012 (pdf).

Top photo: Yu sits in front of a bench top bioreactor in which microbial cells are cultivated for biopolymer production.