Moisture and mold detection in textile flows
In 2022, Swedish textile consumption reached new levels, corresponding to an average of 15.2 kg per person per year. About half is thrown away in residual waste with the final destination of incineration, textiles that could instead have been circulated in the waste stream through reuse, reconditioning, redesign and recycling. To address this, from January 1, 2025, textile waste must be sorted and collected separately from other residual waste, according to the EU's revised waste directive. The directive is mandatory for all member states and aims to increase the collection of textile products and thereby circulate them as long as possible before recycling [1].
Moisture and mold in textiles - a challenge from several perspectives
With the new collection directive, the volume of collected textile and textile waste is expected to increase, putting a strain on existing collection and sorting systems [2]. Regardless of the final disposal channel, it is of utmost importance that the sorted material is dry and mold-free. In Denmark, where municipal textile collection has already started, studies show that over 10% of what is collected is damp/dirty/moldy textile [3]. Mold-infested material has several negative implications:
- Value destruction. One ton of collected textiles can generate up to SEK 100,000 (SEK 100/kg) with sorting and sale in Sweden, depending on quality [4]. If a part is wet and moldy, it can spread and make the whole batch unusable, which leads to a need for sorting. This also drives extra handling costs for (internal) logistics and energy recovery.
- Possible textile and mold particle spreading has a negative impact on the work environment as sorting is currently done manually. Proper handling and protection to prevent mold particles from spreading and creating health problems is recommended [5].
There are thousands of different mold species, and most are odorless. The strongest correlation for mold development is humidity above 60%, i.e. moisture [6]. A working hypothesis has been that innovations such as an electronic nose, which uses measuring probes to detect different chemical compositions as a possible technology for the detection of mold in textile flows. Discussions with suppliers of the technology described the use of the electronic nose in several different industries, including food, environmental monitoring, medicine and security, as well as discussion of possible application in the textile industry. Difficulties such as isolating and analyzing smaller batches of garments in a continuous flow and preventing the electronic nose from analyzing the entire environment are highlighted [7]. Considering that no contacted supplier has previously applied the technology for textile applications, Wargön Innovation assesses the technical conditions as too challenging today, while the need for alternative methods for identification is great. As the correlation between mold infestation and moisture is high, there is good potential to indirectly remove mold-infested material by sorting out moisture in combination with appropriate robotics.
One way to detect moisture is to use near-infrared spectroscopy (NIRS). The technique is well established in the textile industry and is currently used to analyze the material composition of textile materials in sorting and recycling. To analyze moisture, the technology is applied in other industries, including the food and process industries and is used to ensure good quality of products and processes. In tests, Wargön Innovation, together with a technology supplier, has demonstrated the potential for application also in the textile industry [8]. Based on these tests, Wargön Innovation assesses the potential as high. For the application of the technology, the hardware must be supplemented with a data model that is specifically designed to detect moisture in textile materials.
In addition to challenges with mould infestation, wetness also risks interfering with the analysis of material composition by NIRS [9], which has a negative impact in the downstream recycling stage. As a result, it is important to effectively identify and remove damp textiles at an early stage. Often, removal of damp material is done in coarse and/or pre-sorting to minimize the risks of spreading the contamination [10]. NIRS for moisture identification can easily be applied in an early sorting flow, as the equipment is mounted on top of a conveyor belt and can be connected to other control systems for semi- or fully automatic solutions [5]. Technical pilot equipment for automatic identification of wet / possible textile including data model is planned to be made available in Wargön Innovation's innovation environment for industrial textile sorting in 2025 for application in further projects and collaborations.
The correlation between mold infestation and moisture in textile materials is high, which creates the potential to automatically remove infested material by detecting moisture using NIRS in combination with appropriate robotics. The technology for detecting moisture has been applied in several other industries and early tests indicate good potential in the textile industry. As mold-infested and moist material risks spreading and acting to destroy the value of the entire batch, it is important to remove it at an early stage. Wargön Innovation intends to install and make available technical pilot equipment for automatic identification of wet/moldy textiles in 2025.
[1] Swedish Environmental Protection Agency, Textilavfall, 2024-03-04, Textilavfall (naturvardsverket.se), [Retrieved 2024-10-01]
[2] Hedrich, S., et.al., (2022). Scaling textile recycling in Europe - Turning waste into Value, McKinsey & Company. Circular fashion in Europe: Turning waste into value | McKinsey
[3] Interview L. Fyrstenborg, Herning 2024
[4] Interview M. Nilsson, Björkåfrihet 2024
[5] Folkhälsomydigheten, Fukt och mikroorganismer - seminarieserie, 2017, Fukt och mikroorganismer - seminarieserie 2017 - Folkhälsomyndigheten (folkhalsomyndigheten.se).
[6] ibid
[7] Interview Marina, Sensigent 2024
[8] Tests conducted by Wargön Innovation with industry partner (2024)
[9] Becker, Amrei, et.al, 2024 Near-infrared-based sortability of polyester-containing textile waste, Near-infrared-based sortability of polyester-containing textile waste - ScienceDirect
[10] A. Lehmann Enevoldsen, Newretex 2024