Evaluation of spent coffee grounds application in organic fertilizers industry

Abstract

The main purpose of this thesis was to determine chemical and physical properties of spent coffee grounds (SCG) and evaluate their application in organic fertilizers industry. During the experiment, some physical properties, like particle size distribution and pH level of spent coffee grounds solutions of different concentration, were determined. Two different methods have been chosen to determine carbon content in coffee grounds. Also, several instrumental analysis methods have been used to analyse coffee grounds. The results show that spent grounds are not very acidic, values of 10% solution vary between 5.2–5.8. The concentration of organic carbon is quite high and varies between 4.75–5.74%. The TGA and DSC curves show three-stage decomposition. Above 400℃ spent coffee grounds fully decompose. The total mass loss of SCG varies between 97–98%. Functional groups (such as O–H, C=O) were determined by using FTIR spectroscopy. It is clear from XRD that spent coffee grounds are amorphous material. The SEM results show that particles of coffee grounds have high porosity. A drum granulator was used to make granular fertilizers by using water and phosphoric acid solution, but no pellet was obtained without an additional binder.