Converting wood into recyclable and biodegradable plastic

Plastics are one of the biggest polluters in the world, taking hundreds of years to degrade in nature. A research team, led by Professor Yuan Yao and Liangbing Hu of the University of Maryland, has created a high-quality bioplastic from wood by-products that they hope will solve one of the most common environmental problems. most urgent in the world.

Efforts to switch from petrochemical plastics to renewable and biodegradable plastics have proven to be tricky – the production process can require toxic chemicals and is expensive, and mechanical strength and water stability are often insufficient. But researchers have made a breakthrough, using wood by-products, which shows promise for producing more durable and long-lasting bioplastics.

A study published in Sustainability of nature, co-authored by Yuan Yao, assistant professor of industrial ecology and sustainable systems at the Yale School of the Environment (YSE), describes the process of deconstructing the porous matrix of natural wood into a slurry. The researchers claim that the resulting material exhibits high mechanical strength, stability when retaining liquids, and resistance to UV rays. It can also be safely recycled or biodegraded in the natural environment and has a lower environmental lifecycle impact than petroleum-based plastics and other biodegradable plastics.

“A lot of people have tried to develop these types of plastic polymers, but the mechanical strands are not good enough to replace the plastics we use today, which are mostly made from fossil fuels,” Yao explains. “We have developed a simple and straightforward manufacturing process that generates biomass-based plastics from wood, but also plastic which also offers good mechanical properties.”

To create the slurry mixture, the researchers used a wood powder – a processing residue typically thrown away as waste in sawmills – and deconstructed the powder’s loose, porous structure with a biodegradable and recyclable deep eutectic solvent (DES). . The resulting mixture, which exhibits nanometric entanglement and hydrogen bonding between regenerated lignin and cellulose micro / nanofibrils, has high solids content and high viscosity, which can be cast and rolled without breaking.

Yao then conducted a comprehensive life cycle assessment to test the environmental impacts of bioplastic compared to common plastics. Sheets of bioplastic were buried in the ground, fracturing after two weeks and completely degrading after three months; In addition, the researchers claim that the bioplastic can be broken down in suspension by mechanical agitation, which also allows DES to be recovered and reused.

“For me, that’s what really makes this plastic good: anything can be recycled or biodegraded,” Yao says. “We have minimized all materials and waste entering nature.”

Bioplastics have many applications, says Liangbing Hu, professor at the Center for Materials Innovation at the University of Maryland and co-author of the article. It can be molded into a film that can be used in plastic bags and packaging – one of the main uses of plastic and causes of waste generation. Hu also says that because bioplastic can be molded into different shapes, it also has potential for use in automotive manufacturing.

One area that the research team continues to study is the potential impact on forests if the manufacture of this bioplastic is scaled up. While the process currently uses wood by-products in manufacturing, the researchers say they are keenly aware that large-scale production could require the use of massive amounts of wood, which could have implications. profound effects on forests, land management, ecosystems and climate change. name a few.

Yao says the research team has already started working with a forest ecologist to create forest simulation models, linking the growth cycle of forests to the manufacturing process. She also sees an opportunity to collaborate with people who work in forest related fields at YSE – an unusual convenience.

“It’s rare that an engineer can walk down the hall and talk to a forester,” Yao says.

Yao, an emerging researcher in the field of industrial ecology, joined the YSE faculty last year. His research examines the environmental and economic impacts of emerging technologies and industrial processes, integrating interdisciplinary approaches from the fields of industrial ecology, sustainable engineering and systems modeling to develop techniques that promote approaches and policies. more durable engineering.

Reference: “A solid, biodegradable and recyclable lignocellulosic bioplastic” by Qinqin Xia, Chaoji Chen, Yonggang Yao, Jianguo Li, Shuaiming He, Yubing Zhou, Teng Li, Xuejun Pan, Yuan Yao and Liangbing Hu, March 25, 2021, Sustainability of nature.
DOI: 10.1038 / s41893-021-00702-w