Chemical Recycling Repurposes Diapers into Adhesives Removing Millions of Sodden Diaper Wastes

As mundane as it seems, but disposable diapers are a billion-dollar industry. According to RealDiapers, 92% of diaper wastes get buried in landfills, with disposable diapers being the third largest consumer item in landfills. Unfortunately, this spells a grave threat to the environment since diapers need more than 500 years to decompose.

Disposable Diaper Conundrum

(Photo: Public Domain Pictures by Pexel)

Diapers are favored by many because of their exceptional superabsorbent quality. Unfortunately, it is this matrix of polymers that cause such a problem in the Solid Waste department. Whether manufactured or natural, polymers are made up of massive long-chain molecules, with polyacrylic acid serving as the absorbent ingredient in disposable diapers.

To respond to the need for diaper disposal, a team of University of Michigan researchers devised a novel method for untangling absorbent polymers and recycling them into adhesives similar to those used in bandages and sticky notes, according to Michigan News.

Note that recycling can be categorized into two groups: chemical recycling and mechanical recycling.

According to Anne Mcneil, co-author of the paper and a chemist at the Univerity of Michigan, mechanical recycling is when people segregate and separate various plastics based on the type and incinerate and reuse the material that results in lower quality of products, reports ScienceDaily.

The reduction in the quality of mechanical recycling is caused by different plastics constructed differently. Some have longer chains that can be altered with different dyes and additives, but that is not applicable for all. The study authors note that there are many problems with mechanical recycling. Hence, chemists are using chemical transformations to develop value-added material.

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Chemical Recycling Sodden Diapers

The characteristics that make plastics a vital consumer product, such as their durability and toughness, are equally responsible for the problems in recycling, especially with polymers that are extremely difficult to break down since they are closely held together by stable bonds.

In a study published in the journal Nature Communications, "Giving Superabsorbent Polymers a Second Life as Pressure-Sensitive Adhesives," McNeil, in collaboration with Takunda Chazovachii, a recent doctoral degree graduate at the University of Michigan and Procter & Gamble, developed a unique 3-step process that recycles superabsorbent polymers of disposable diapers into adhesives. The method is not only energy-efficient but can also be industrialized.

Chazovachii explained that superabsorbent polymers are expected to be non-recyclable due to their design specifically for water retention, making them non-biodegradable. Luckily the polymers and adhesives are similarly derived from acrylic acid that inspired the team's idea of chemical recycling.

The team used sonication that utilized tiny air bubbles to break the polymer bonds without changing their inherent chemical properties. As ScienceDaily reports, the process is similar to a mild mechanical process where the polymer chains are broken down, but the building blocks and acid groups are left intact to allow researchers to foster new chemical reactions.

Researchers were also able to figure out how recycling diapers into adhesives was more eco-friendly than developing adhesives from petroleum, which is the typical case. The study authors found a 22% reduction in the potential of global warming using the 3-step technique and a reduction in energy of 25%.