Waste plastics-integrated agro-waste formulations for durable exterior and interior interlock and roofing sheets in sustainable construction

Abstract

Global plastic waste generation exceeds 400 million tonnes annually while agricultural residues surpass 4–5 billion tonnes, creating an urgent dual challenge for sustainable construction. This systematic review evaluates the potential of waste plastics-integrated agro-waste composites as durable, cost-competitive alternatives to conventional roofing sheets, interlocking tiles, and interior ceiling panels. By synthesizing recent studies (2020–2025), the analysis shows that hybrid formulations combining post-consumer high-density polyethylene (HDPE), polypropylene (PP), polyethylene terephthalate (PET), and mixed plastics (30–60 wt%) with agro-residues such as rice husk, sugarcane bagasse, palm kernel shell, and coconut husk (20–50 wt%) can achieve exterior-grade performance, including impact strength of 18–35 kJ/m2, flexural strength above 30 MPa, water absorption below 2%, ultraviolet (UV) retention exceeding 85% after 2000 h xenon-arc exposure (QUV), and fire classification B-s1, d0 per EN 13501-1. Interior applications demonstrate noise reduction coefficients of 0.55–0.75, total volatile organic compound (TVOC) emissions below 150 μg/m3, and fungal resistance rating 0–1. Despite these advances, fewer than 5% of formulations incorporate more than three waste streams simultaneously, and long-term weathering data equivalent to over 15 years remain scarce. Key barriers include inconsistent feedstock quality, poor interfacial bonding in contaminated streams, and the absence of product-specific standards. The study proposes a 2026–2035 roadmap integrating machine-learning-assisted multi-waste formulation design, regional waste-to-roofing hubs, and harmonised International Organization for Standardization (ISO) certification. Successful implementation could enable these composites to capture 20–30% of the global roofing and interlocking tile market by 2035 while significantly reducing embodied carbon.