Assessment of Textile Waste Circularity through Composting Using the Seed Germination Index as Indicator for a Sustainable Management

Nowadays, the world is dealing with a textile waste management problem that affects both human health and the environment. As one of the cornerstones of the circular economy, composting is described as an effective green technology for recycling of such type of waste. The further usage of such compost is not possible without examination of the genotoxic and phytotoxic effects of the final product. Here, we examined the effect of initial feedstock concentration on the biosafety of textile compost. Three mixtures were analyzed using textile waste mixed with green waste and paper and cardboard waste as the input feedstock. Such mixtures were processed by the silo composting method and the phyto-toxicity of the obtained compost was assessed using the germination index. Moreover, to explain the results obtained, analysis of physical-chemical parameters (pH, electrical conductivity, carbon/nitrogen (C/N) ratios, ammonium and nitrate ratios, and humic substances ratio (E₆/E₄)) as well as total heavy metal (Cr, Cu, Ni and Zn) and Na⁺, P, K+, Mg²⁺ and Fe contents were determined in initial mixtures and final compost products. Mixtures with 40% and 60% of textile waste at the final stage of composting were non-phytotoxic, with a germination index above 100%, a C/N ratio between 15 and 20, NH₄⁺/NO₃⁻ ratios below 1 and E₆/E₄ close to 5. All composts, even with a high concentration of textile waste (80%), fulfilled the requirements of the Canadian national standard for heavy metal content. This study proves that well-managed composting, whatever the nature of the feedstock and/or the concentration used, produces a high-quality organic amendment which increases the yield and quality of plant biomass.