Valorization of Doum Palm Fibers and EPS Waste into Lightweight Bio-Composites for Energy-Efficient Buildings

The building sector accounts for a large share of global energy demand and CO₂ emissions, underscoring the urgent need for sustainable insulation solutions. This study develops lightweight bio-composite panels by combining Doum palm fibers (Hyphaene thebaica), a locally available by-product, with a recycled expanded polystyrene binder (EPSB) derived from post-consumer waste. Composite formulations with fiber contents of 40%, 50%, and 60% were fabricated and characterized for density, thermal conductivity, and thermal diffusivity using the transient Hot Disk technique. Increasing fiber content markedly reduced density while improving insulation performance. The DFE60 composite (60% fiber, 40% binder) exhibited the best properties, with a thermal conductivity of 0.1156 W·m⁻1·K⁻1 and a diffusivity of 0.1952 mm²/s. To evaluate real-scale performance, a TRNSYS simulation was carried out for a typical building in Oujda, Morocco (semi-arid climate). Incorporating a 4 cm DFE60 layer into the envelope lowered annual energy demand by 37%, with cooling and heating loads reduced by 41% and 37%, respectively. These results highlight the potential of Doum palm fiber–EPS composites as a sustainable, low-cost alternative to conventional insulation, valorizing local biomass and plastic waste while enhancing energy efficiency in buildings.