The textiles investigated in the project cannot be recycled on a large and cost-effective scale today.
– We are investigating how textiles consisting of fiber mixtures can be recycled thermochemically in a plastics recycling refinery. These materials can’t be fiber recycled with reasonable effort today, and most of it is incinerated, says Martin Seemann, project manager and associate professor at Energy Technology, Chalmers.
Thermochemical recycling means that the molecules are recycled from textiles instead of whole textile fibers. The small molecules can then be used as a recycled raw material to produce new valuable base chemicals and materials, both as a base for new textile fibers and other materials where fossil base chemicals are used today.
In the process, the textiles are heated up to 600-800 degrees, which in short means that the material is divided into a liquid and a gaseous fraction. The liquid fraction becomes building blocks for new material and the gas fraction can be used to reconnect the building blocks.
– This means that you can use basically all of the material to create new fibers. But it is something we will evaluate and test in the project. And with a reasonable effort of, for example, energy. It is about finding the optimal point in this process and if there is a procedure that is more advantageous than the alternatives, says Martin Seemann.
The textiles that are investigated in the project "Recycling of reject streams from textile sorting and cardboard recycling", are those that cannot be recycled on a large scale and cost-effectively with other technologies today. The main focus is to get as much useful material out of the process as possible. Then the material could be used as raw material in the textile industry, but also in other industries.
First tests are positive
In Sweden today, about 7.5 kg of textile per person and year is thrown out with the household trash. There is a proposal for producer responsibility for textiles from 1 January 2024, , in which case the industry will be responsible for collecting this quantity and preparing for recycling. This means that the more than 70,000 tonnes of textiles, which today end up in Sweden's residual waste, will be handled in another way.
At the end of January, the project’s first test was performed with a positive result. During the month of March, another test was performed where 1-2 tons of textile material were converted into pellets.
– It also went very well, which feels extremely exciting in the future, but we must not forget that we are at the beginning of the development and there is still a lot to learn, says Martin Seemann.
The project "Recycling of reject streams from textile sorting and board recycling" started in November 2020 at Chalmers with funding from the West Swedish Chemistry and Materials Cluster (via the Vinnväxt project Climate-Leading Process Industry) and the Swedish Textile Research Foundation (SST).
The goal of the project at Chalmers is to increase society's resource efficiency, circularity, reduce CO2 emissions and increase the competitiveness of Sweden and Swedish companies in the long term. The project also meets a number of environmental goals in Agenda 2030. The project includes actors from the recycling industry, the chemical industry and the textile industry. Sorting and processing in the form of Wargön Innovation are also involved, as is the Swedish University of Agricultural Sciences (SLU).