Sustaining Natural Dye Plants with Post-Consumer Textile Waste

Aligned with the circular economy framework, this study aims to address pertinent research gaps regarding material and chemical properties of clothing and suitability for closed-loop applications. Primary research questions include: (1) what are the material and chemical properties of post-consumer textile waste from a sustainable fashion take-back program; (2) which natural post-consumer textile waste is most suitable to support the growth of natural dye plants in a hydroponics system; and (3) can the use of post-consumer textile waste in a hydroponics system be scaled to support a circular fashion supply chain? This study focuses on wool, cotton, linen, silk, rayon, and Tencel® lyocell as substrates to nurture the growth of purple basil, a natural dye plant. Vertical hydroponics is a farming method that uses nutrient water to grow plants in place of soil throughout the year. The system can be indoors, making resourceful use of limited space available and the water is recirculated. Standard hydroponic substrates, like peat moss and rockwool, have good porosity for oxygen transport and suitable moisture holding capacity for nutrient delivery. In this study, we compared the performance of the standard hydroponic substrates with various textiles. The impact on water quality, color release, moisture wicking, stability against degradation, and survival rate of the plants was used to evaluate suitability in the application. Wool, silk, and Tencel lyocell demonstrated good durability in the hydroponic system, like peat moss and rockwool, during the first growth cycle. During the second growth cycle, protein fibers—wool and silk—supported plant survival at a greater capacity than Tencel lyocell. Future research can confirm that wool and silk can support the growth of natural dye plants with a larger sample size. This research aligns with several circular economy objectives and provides a model for future research to support circular fashion supply chains.