Recycling Textile Waste into High-Strength Packaging Paper

Researchers from TU Graz have developed a method for recovering fibers from used cotton textiles and converting them into paper for packaging. The paper made from textile fibers is significantly stronger than standard recycled paper.

Around 80%  of the 220,000 tons of textile waste produced annually in Austria is burned, resulting in the loss of valuable raw materials. Old clothing is mostly incinerated, but it is possible to extract the cellulose fibers from used clothing and convert them into cardboard and other packaging materials using modified paper production methods.

A team from the Institute of Bioproducts and Paper Technology, led by Thomas Harter, has developed a long-term solution to this issue.

Strictly speaking, the conversion of textile fibers into paper is a downgrade. However, it has a major advantage from an environmental point of view. The paper cycle is highly closed, with recycling rates of over 90 % in the packaging sector. If we bring valuable textile fibers into this cycle, they remain usable for a long time.

Thomas Harter, Head, Institute of Bioproducts and Paper Technology, TU Graz

Recycled textiles can reduce the amount of paper imported for packaging production and provide a valuable source of raw materials.

Very Similar to Normal Papermaking Suspension

Old clothing is first shredded into small pieces and then soaked in an aqueous solution to create paper. The goal of milling the water and shredded mixture is to separate the interwoven cotton fibers without causing them to clump or knot. As part of his master's thesis, Alexander Wagner identified the optimal beating machine, processing time, and water-to-textile ratio, which were crucial for extracting the most usable fibers from the textile waste.

At the end of our tests, we obtained a suspension that is very similar to a normal papermaking suspension and that we can process into paper using established methods.

Thomas Harter, Head, Institute of Bioproducts and Paper Technology, TU Graz

Significantly More Tensile Strength than Conventional Recycled Paper

In terms of appearance, the textile-content paper closely resembles regular recycled paper, with a slightly brownish hue and occasional flecks of color from dyed garments. However, cartonboard and other packaging materials are not affected by these color variations. Tensile tests have shown that recycled paper becomes stronger when textiles are added.

Even with a textile-based proportion of 30 %, the paper is significantly stronger, while the processability remains the same.

Alexander Weissensteiner, Master Student, Institute of Bioproducts and Paper Technology, TU Graz

The fiber lengths of recycled waste paper are quite short. At 1.7 mm, our recycled textile fibers are significantly longer,” said Weissensteiner.

The researchers' next goal is to reduce the energy consumption of the beating process. In addition to using additives like mild acids and alkalis, they are also testing enzymatic pre-treatments to help break down fibers in the beating unit.

 “We also want to take the next scaling step and implement the process on industrial devices,” said Thomas Harter.