<p>Rotational moulding (RM) is a versatile technique for producing plastic products, but its environmental sustainability needs deeper analysis. Existing life cycle assessment (LCA) studies are often limited, focusing on single materials and ignoring variations in process parameters. This study introduces a parametric LCA model designed to minimize the environmental impact of RM composite products by optimizing material composition, specifically blends of polyethylene and natural fibre (e.g., abaca). The model allows users to set control parameters, including product dimensions, mould material and thickness, energy consumption, from gas furnace and motor, number of moulds, geographical location, and the impact category to assess. Applied to case studies with abaca fibre composites, the model demonstrated that optimizing the fibre-to-polymer ratio can significantly reduce environmental impacts. These reductions vary depending on the input parameters, confirming that a one-size-fits-all approach is inadequate. The model’s ability to process multiple heterogeneous factors makes it a robust tool for eco-assessment. It supports systematic sensitivity analysis and offers practical, flexible guidance for eco-design in RM, particularly for multi-material products. Its strengths, flexibility, low cost, and ease of integration make it especially valuable for small and medium-sized enterprises with diverse product lines, enabling more sustainable decision-making without requiring extensive resources.</p> Graphical abstract <p></p>