Development and validation of corncob as a sustainable building and construction material

Abstract

Motivated by the urgent need to reduce waste, embodied carbon, formaldehyde exposure and cost in the building and construction sector, this thesis develops and validates a formaldehyde free CCPB as a sustainable alternative to conventional wood-based panels. Corncob (CC), an abundant but underutilised agricultural residue, was investigated as the principal lignocellulosic furnish, while soy protein isolate (SPI) was engineered as the bio-adhesive system. The study integrates multi-scale material characterisation, adhesive formulation, rheological profiling, design of experiments, response-surface optimisation, comparative panel testing, and techno-economic and carbon assessment. CC was shown to be a hierarchically organised biomaterial comprising a porous pith, dense woody ring, and silica-enriched glume, with an average compressive strength of 67.6 MPa and tensile modulus of 191.19 MPa, confirming its suitability as a non-wood particleboard furnish. Four SPI adhesive formulations were developed and benchmarked against urea-formaldehyde resin. The optimised formulation, SPI-4, exhibited improved storage stability, gel strength, and mould resistance over 56 days, together with rheological properties compatible with board manufacture. Based on particle board (PB) hot pressing process, a six-factor response-surface study established the optimum processing window at 150 °C, 88.89 bar, 15 minutes, 50 wt% SPI solids, and finer particle fractions. Under these conditions, the developed corncob particleboard achieved internal bond strength of 0.81 MPa, modulus of elasticity of 2.1 GPa, and modulus of rupture of 15.8 MPa, while formaldehyde emissions were non-detectable. Performance benchmarking showed compliance with ISO 16893 requirements for interior, general-purpose, and non-structural applications. Cradle-to-gate assessment further showed that CCPB achieved a 17.3% lower carbon footprint than the wood–urea-formaldehyde baseline, equivalent to a net reduction of 420.7 kg CO₂ m⁻³. Economic analysis indicated that the SPI adhesive cost £1.45/kg compared with £10.50/kg for urea-formaldehyde, representing an 86.2% raw-material cost reduction, and that the system becomes cost-competitive under industrial scale-up. Overall, the thesis advances CC from agricultural waste to a technically viable, lower-carbon sustainable construction material.

Date of Award	2025
Original language	English
Awarding Institution	Canterbury Christ Church University