Coffee processing shapes sensory quality while simultaneously transforming plant biomass and generating side streams that may be valorised. This study evaluates the biological and chemical effects of liquid maceration of coffee beans and discusses the resulting side streams within a circular-economy and environmental-engineering framework. The investigated parameters included moisture, acidity, pH, protein, surface fat, caffeine, trigonelline, carboxylic and hydroxycinnamic acids, sugars, melanoidins, brew colour, instrumental aroma and taste, and microbiological quality. Maceration modified the physicochemical profile of the beans: caffeine and trigonelline contents decreased, organic-acid profiles changed, and the processed material remained microbiologically stable. The process should therefore be assessed together with the spent maceration medium and the coffee silverskin generated during roasting. Both streams may contain recoverable compounds or material fractions suitable for further valorisation. Linking bean modification with side-stream management supports cascade use of coffee biomass and provides a basis for further research on extraction, bio-composites and other environmental-engineering applications.