Résumé
While the world remains dependent on fossil fuels in nearly every aspect of life, unused biomass is piling up as waste, despite its significant potential for valuable applications—a critical missed opportunity for sustainable innovation. Phase change materials (PCMs) have emerged as a pivotal technology in the urgent transition toward carbon neutrality, especially considering that heating and cooling consume nearly half of global energy expenditure. This comprehensive review advances the scientific understanding of sustainability and circularity in PCM fabrication by providing a strategic framework for developing composites from renewable resources. This framework involves the introduction of a novel classification system (types 0–3) for biomass‐derived PCMs based on their levels of modification, enabling a comparison of material sources, performance metrics, and environmental impacts. By showing recent innovative developments in PCM shape stabilization, thermal conductivity enhancement, and leakage protection, it critically highlights the opportunities to replace conventional materials with innovative biomass‐derived alternatives, such as biomass‐derived carbons and polymers. Furthermore, the study integrates tools aligned with the Principles of Green Chemistry to aid the fabrication of truly sustainable materials, helping to guide researchers through material selection, process optimization, and the comprehensive evaluation of the environmental impact associated with their use and disposal.