The hidden environmental footprint of fashion’s smallest parts

• First life cycle inventory of trims & accessories for apparel LCAs. • Metal-based T&As dominate T&A environmental hotspots. • Omitting T&A leads to underestimated (1 %−6 %) results in garment life cycle studies. • 75 % of T&A emissions embedded in EU & USA exports from Bangladesh. • Recycled inputs and renewable energy can cut T&A GHG emissions by up to 48 %. As one of the world’s leading exporters of ready-made garment (RMG) products, Bangladesh provides a strategically relevant context for examining overlooked aspects of garment supply chains. Despite their functional and economic importance in the RMG industry, trims and accessories (T&A) are rarely captured in life cycle assessments (LCAs), primarily because methodological frameworks struggle with product heterogeneity, diverse performance requirements, fragmented supply chains, and missing inventory data – factors that collectively bias results toward underestimating sectoral impacts. To address this gap, we present the first comprehensive life cycle inventory (LCI) of major T&A, designed for direct integration into apparel LCAs. Impact assessment reveals that while most items have modest impacts in all categories owing to their small size, zippers and buttons, particularly metal-based ones, exhibit disproportionately high burdens from energy-, water-, and chemical-intensive electroplating. Garment-level modelling demonstrates that excluding T&A leads to systematic underestimation of total impacts and distorts the allocation of environmental pressures across product components. A typical exported garment carries 1%–6% additional greenhouse gas (GHG) emissions from its T&As, and these can be reduced by up to 26% through recycled materials and 48% by using renewable energy in the production. Scaling to Bangladesh’s export trajectory suggests that life cycle GHG emissions from the T&A sector may rise by 313% by 2050 but could be cut by >56% under deeper circular economy and decarbonisation strategies. Embodied emission analysis further shows that nearly three-quarters of the total T&A-related greenhouse gas burden is embedded in exports to Europe and the USA, highlighting the need for trade-linked climate strategies and collaborative interventions between producers and consumers. Although developed using Bangladesh as a case study, the dataset produced in this study can be adapted globally by substituting country-specific background data. Beyond providing a foundational LCI for practitioners, this study offers evidence-based insights for policymakers and industry stakeholders, including brands, retailers, and manufacturers, to guide the textile and RMG sectors towards more sustainable supply chains.