<p>This research aimed to obtain materials with controlled-release properties by compounding a commercial nitrogen-phosphorus-potassium fertilizer into biodegradable matrices, with or without used coffee grounds. Polybutylene adipate-co-terephthalate (PBAT) and a biodegradable polymer based on polylactic acid (PLA) were used as polymeric matrices. Upon compounding by extrusion, composites were converted into plates through compression molding to evaluate their morphological properties, water degradation capacity (weight loss), and subsequent nutrient release (catarometry and inductively coupled plasma optical emission spectrometry). Additionally, composites were injection molded and characterized for their mechanical properties to assess the effect of polymer type and filler content. The incorporation of spent coffee grounds by itself proved to be poor in nutrient release. However, in composites containing fertilizer, the addition of coffee grounds appears to influence water degradation and subsequent nutrients release. Scanning electron microscopy analysis highlighted the influence of coffee grounds as a degradation-enhancing agent. Furthermore, the inclusion of coffee grounds in the polymeric matrix increased the stiffness of the composites, which can be attributed to the intrinsic rigidity of lignocellulosic materials.</p> Graphical Abstract <p></p>