Green Biocomposites Based on Spent Coffee Grounds

The continuous growth of the coffee market generates enormous amounts of spent coffee grounds (SCG), which account for up to 95 % of waste after coffee consumption. SCG contain a wealth of different resources that just need to be converted into another usable form. On the other hand, to- day's excessive production of plastic waste in almost all industries worldwide is causing significant environmental pollution, leading to increased use of biodegradable polymers and biocomposites. Precisely because of the enormous amounts of SCG and the slow biodegradability of polylac- tide (PLA), this study aimed to investigate the properties and biodegradability of biocomposites made from green PLA and SCG, which were prepared by mixing the PLA matrix with different proportions of SCG. The thermal properties of the biocomposite were investigated by differential scanning calorimetry and thermogravimetric analysis. The particle size distribution of the SCG was studied by laser diffraction method, as well as the water absorption. The biodegradation of the biocomposite was carried out by a composting process of 19 days. The results of the thermal properties test showed that the SCG as filler did not affect the phase transitions of the PLA matrix, but it did affect the reduction of the thermal stability of the PLA_SCG biocomposite. The results of the water absorption test showed that increasing the amount of SCG leads to an increase in water absorption in biocomposites, due to the hydrophilic nature of the filler. On the light micro- scopic images, the surface attack of microorganisms was visible in biocomposites with lower SCG content, while deeper penetration was observed in biocomposites with higher SCG filler content.