Natural wax supported by microporous biochar to create a stable phase change material

Energy storage, exploiting the latent heat of phase change materials, offers an efficient method to store and release heat. Initial developments of phase change materials and their containment targeted performance over environmental impact. This article presents a bio-sourced, fully compostable, and biodegradable composite phase change material made from hardwood charcoal and beeswax. This material combines effective heat transfer performance with a significant focus on sustainable end-of-life waste management, especially when compared to traditional methods that rely on synthetic or heavily modified bio-sourced phase change materials. We measured a beeswax uptake within charcoal's porous structure of up to 61.2%. This resulted in a composite with a latent heat enthalpy of 77.83 J g−1, with cyclability tested up to 20 cycles without any reduction in performance. The process was scaled from millimetre-scale particles up to centimetre-scale particles with similar adsorption capacities. The Laplace–Young equation confirmed that adsorption of beeswax is mostly driven by a capillary pressure, of at least 2.2 × 104 N m−2, caused by the naturally occurring porous structure of charcoal. These beeswax-loaded charcoal particles could find applications for heat recovery in HVAC systems or in packed bed heat storage systems.