Pelleting spent coffee grounds by waste utensils as binders of biofuels

New generations of biofuels innovative combined (bio-)waste resources of spent coffee grounds (SCGs), chopsticks, and polypropylene (PP) spoons were successfully achieved in this study. The SCG pellets were compressed at load force of 40 kgf/cm(2) for 3 min and torrefied for 1 h at 300 degrees C during the manufacturing processes. The highest heating value of the sample was 26.21 MJ/kg with 50% SCGs, 20% chopsticks, and 30% PP spoons. The solid yields of chopsticks and PP spoons were ca. 2.45% (w/w) and 3.35% (w/w) when increasing 10% of the waste utensils, respectively. The content of the fixed carbon was in a range of 17-34.68% in the SCG samples. Mixing chopsticks is helpful for increasing fixed carbon content, and PP spoons is helpful for increasing heating values of the biofuels. The TGA results found that decreasing SCG contents increased weight loss of the samples within experimental period. The SEM images showed an incorporation of SCG with waste utensils formed a homogeneous and continuous surface with a good compatibility. The SCG samples manufactured in this study had higher carbon contents (70.40-78.34%) than previous studies of SCGs. Using PP utensils did not contribute chlorine contents (0%) but small contribution of sulfur (0.41%) and chlorine (0.10%) contents of the samples were from chopsticks. The results of this study are useful for reducing wastes and creating renewable energy in the modern energy demanded world.