(661d) Pelletization of Spent Coffee Grounds

Different types of raw materials as biomass can be densified to be used as biofuels. The produced pellets provide an alternative to solve the energy problem. With the densification, it is not only possible to improve the combustion process (increasing the calorific value). It also helps to solve the problems associated with loading, transporting and storing the product (thanks to the increased density).

In this project pellets were made of spent coffee grounds. Three kinds of these were characterized, from different sources. After this, the most appropriate biomass was selected to be used as fuel, according to three selection criteria: moisture content, ash content and superior calorific value. The pellets were made using not only the moisture content of the biomass, but also three other products as a binder: glycerin, crude palm oil and biodiesel.

The biomass with a moisture content of around 70% was dried in an oven at 80°C. Subsequently, pellets with different concentrations of moisture within the range between 4% and 20% were produced, obtaining a consistent product between 5% and 15% moisture. After defining the moisture range, the concentrations of each of the binders were varied between 2% and 10%. Pellets were formed between 2% and 8% concentration of binders, using moisture material between 4% and 8%.

Once the moisture content and concentration of binders were defined, a factorial design of experiments was carried out to obtain a response surface. The obtained pellets were characterized physically, chemically and mechanically, according to the German standard DIN 51731 for solid biofuels.