Thermal Conductivity and Structural Performance of Natural Insulation Materials in Refrigeration: A Review

Abstract

The growing need for sustainable and energy-efficient refrigeration systems has sparked research into eco-friendly insulation options. This review looks closely at the thermal conductivity and structural performance of natural insulation materials, especially fiber-reinforced bio-composites, for refrigeration use. Traditional materials like polyurethane and polystyrene are efficient but create environmental issues and challenges at the end of their life. On the other hand, natural fibers like coir, jute, banana, hemp, sugarcane bagasse, and calabash provide low thermal conductivity, high porosity, and biodegradability, which support global sustainability efforts. The review is based on twelve peer-reviewed studies published between 2010 and 2025. It examines the behavior of composites concerning thermal conductivity, specific heat capacity, density, porosity, and compressive strength. Coir/jute and banana-eggshell composites show a good balance of thermal insulation and mechanical strength, while calabash-based composites are promising for low-temperature settings. However, challenges like moisture absorption and scalability still exist. The review suggests using optimization methods such as RSM and DoE for further improvements. In conclusion, bio-composites are viable candidates to replace synthetic insulators in refrigeration, as long as further research focuses on durability, fire resistance, and lifecycle cost.