Transesterification and Densification in Solid Waste Treatment Systems: A Narrative Conceptual Review of Physicochemical Methods

Abstract

The increasing generation of organic solid waste due to population growth, urbanization, and industrial activities requires management systems that not only reduce waste volume but also promote sustainable resource and energy recovery. This article presents a conceptual review of the integration of transesterification and densification as physicochemical methods in solid waste treatment. The study uses a narrative conceptual review approach based on scientific literature published between 2020 and 2025, focusing on process principles, reaction mechanisms, feedstock characteristics, and integration potential within a waste-to-energy framework. The findings indicate that transesterification converts the lipid fraction of waste into biodiesel as liquid energy, while densification improves solid residues into biomass fuel with higher energy density and stability. The integration of these processes can enhance energy recovery efficiency, reduce waste volume, and lower greenhouse gas emissions. However, implementation still faces challenges, including waste heterogeneity, the need for pre-treatment, and optimization of material and energy flows. Conceptually, the integration of transesterification and densification shows strong potential as an innovative approach to sustainable solid waste management, supporting circular economy strategies and the transition toward low-carbon waste-to-energy systems.