Evaluation of the Energy Density for Burning Disaggregated and Pelletized Coffee Husks

Coffee husks represent about 12 wt % of coffee grains, generating a significant impact on the environment because of its inadequate disposal. In Colombia, this waste presents an energy resource opportunity equivalent to over 49,106 TJ per year. However, several challenges related to this type of biomass, such as the moisture content, the irregular shapes, and the low bulk density, make its use difficult in current burners. Thus, in this paper, the combustion of coffee husk pellets was studied in detail to design a high-efficiency burner to produce energy for coffee drying. The pellets were prepared in a pelletizer with 15% moisture and 20% yield and burned in a bench-scale lateral reactor to determine the energy density. It was found that the combustion properties of coffee husk depend on the specifics of the pelleting process. The energy density values were Iv = 0.789 MW/m3 and Ig = 0.007 MW/m2, which could be used to design the combustion chamber for coffee husk burning.