Sodom Apple (Calotropis procera) Fibre as a Sustainable Thermal Insulator: Performance Evaluation for Low-Carbon Thermal Storage Systems

Abstract

Thermal insulation materials are critical to energy-efficient thermal management systems, impacting food preservation, vaccine cold chains, and building energy use. While expanded polystyrene (EPS) foams dominate insulation applications due to low thermal conductivity and lightweight structure, they present significant environmental challenges, including non-biodegradability, microplastic generation, and high embedded carbon. This study evaluates Calotropis procera (Sodom Apple) fibre as a sustainable, bio-based alternative for thermal storage. Mature fruits were harvested in Maiduguri, Nigeria, fibres were extracted, cleaned, sun-dried, and compacted to <32 kg/m³ bulk density. A double-walled aluminium storage box with a 25 mm insulation cavity was fabricated, and steady-state conduction was modeled using Fourier’s law. Thermal retention tests benchmarked the Sodom Apple fibre system against conventional EPS enclosures over 300 minutes. The bio-based insulation sustained temperatures above 60 °C for 5 hours, achieving 84.7% of EPS performance (k = 0.066 Wm⁻¹K⁻¹, Rins = 0.379 m²•K/W). The fibre’s hollow tubular morphology and air entrapment suppress convection and reduce radiative transport, providing functional equivalence under operationally relevant durations. These findings demonstrate that lignocellulosic fibres can deliver practically viable thermal performance while significantly reducing environmental impact, supporting the development of circular, low-carbon thermal management systems.