With a simple, inexpensive treatment, researchers have found a way to make paper bags strong enough to be reused multiple times, even when they get wet. The bags could be a true ecofriendly alternative to single-use plastic bags.
At the end of their lives, the durable paper bags can be broken down to be used as biofuel. “The implications of a technology like the one we demonstrated in this research… including using the worn-out bags as a substrate for biofuel production, would be huge,” said lead researcher Jaya Tripathi in a press release. Tripathi and her colleagues at Penn State University presented their work in the journal Resources, Conservation and Recycling.
The world makes five trillion plastic bags a year. Each bag takes over 1,000 years to decompose. A significant share of these wind up in waterways and oceans, littering the environment and harming wildlife. And even if they get to landfills, they can harm the environment because they eventually break down to produce harmful microplastics and toxic chemicals.
Paper bags are not only made from a renewable resource, they also decompose much faster than plastic bags, and present less danger to animals. But that does not necessarily give them an entirely clean environment bill.
It takes a lot of energy to make paper bags, and because they are heavier than plastic, they take more energy to transport, translating to higher carbon emissions per bag. Some studies have shown that paper bags need to be reused anywhere from three to 43 times to make them more environmentally friendly than plastic bags.
Problem is, paper can be flimsy and doesn’t hold up well when soggy. So Tripathi and colleagues came up with a chemical process that makes them stronger. The technique, called torrefaction, involves heating the paper slowly in a low-oxygen environment. This makes the cellulose fibers in paper more water-repellant, makes it stronger even when wet.
In their study, the team found that the strength of filter paper increased by a high of 2,233% after 40 minutes of heating at 220°C. While the strength increases, however, torrefaction decreases the glucose content in the paper, which brings down its usefulness as a biofuel. The researchers’ answer to this was to treat the paper with a sodium hydroxide solution, which boosted the glucose content.
The researchers will have to translate their laboratory work to practical paper bags of course. But the implications could be big. Americans throw away 100 billion bags annually. “By switching to stronger, reusable paper shopping bags, we could eliminate much of that waste,” Tripathi said.
Source: Jaya Tripathi, Daniel Ciolkosz, and Dan G. Sykes. Torrefied paper as a packaging material and subsequently as a bioethanol substrate: Synergy of torrefaction and alkaline treatment for increased utility. Resources, Conservation and Recycling, 2023.
Image: ©Anthropocene Magazine