Eco-designed Polyethylene Composites with Postconsumer Diatomaceous Earth

The reuse of industrial solid waste in polymeric materials represents an important strategy for sustainable resource management, contributing to waste valorization, landfill diversion, and resource efficiency within a circular economy framework. This study investigates eco-designed composites of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) reinforced with 5 wt % diatomaceous earth (DE) recovered from brewery filtration residues. Raw DE and postconsumer DE dried using a disaggregator (DE-DisaggregatorDry) or spray dryer (DE-SprayDry) were characterized by XRF, XRD, particle size distribution, and FEG-SEM analyses. The composites were produced by melt mixing and compression molding followed by mechanical, thermal, morphological, and rheological analyses. DE-SprayDry generated finer and more uniform particles, improving dispersion and HDPE performance, with a 34% increase in elastic modulus, 3% hardness improvement, and minimal impact strength reduction. DE-DisaggregatorDry showed an intermediate behavior, whereas DE-Raw caused agglomeration and mechanical deterioration. In LDPE, reinforcement was limited. Overall, DE-SprayDry demonstrated the best performance, highlighting postconsumer DE as a sustainable filler for eco-designed polymer composites. Considering that approximately 30,000 kg of DE is discarded monthly, the proposed approach offers a sustainable alternative for industrial waste management and the development of value-added polymeric materials.