Improving the biodegradation and durability of rice straw composites via coatings and pretreatments

Abstract

The utilization of agrarian waste such as rice straw in construction materials is limited by its high moisture sensitivity and susceptibility to biodegradation. At the same time, building energy consumption accounts for approximately 40% of global greenhouse gas (GHG) emissions worldwide, highlighting the urgent need for construction materials with minimal or near-zero carbon footprints. This present work investigates rice straw waste composites that can serve as a sustainable alternative in building sandwich constructions. The effect of three different coatings, viz., adhesive binder, epoxy resin, and polyethylene terephthalate (PET), on the biodegradability of rice straw composites is evaluated. The effect of water and alkali pre-treatment on rice straw is also evaluated through biochemical testing, water absorption, soil burial experiments, and microstructural characterization. The investigations suggest that the coatings can improve the structural integrity of rice straw and hence their durability. In comparison to the uncoated stubble waste composites, the weight loss of epoxy and PET-coated stubble waste composites reduced by ~65%–70%. Both coated and uncoated rice straw composites showed much lower thermal conductivity in comparison to the conventional building materials, highlighting their suitability for the development of building thermal envelopes.