Environmental impact assessment of a cocoa shell pellet (CSP) combustion system: Effects of integrating an emission filtration system

Abstract

Densified biomass in the form of pellets, made from cocoa shell pellet (CSP), represents a renewable thermal energy source. Experimental combustion tests and emission readings were then conducted over 15 minutes, both with and without the filter, resulting in significant average improvements; with CO levels decreasing from 1710 to 475 ppm, CO₂ levels dropping from 2.13% to 0.2%, H₂S levels reducing from 39.36 to 5.7 ppm, and N₂ decreasing from 76.64% to 74.71%. O₂ levels increased from 15.06% to 17.02%. This assessment showed a modification of environmental impact assessment with the installation of the filtration system, reducing the negative impacts from 18 to 13. It changed from a medium-impact project (without filter) to a low-impact project (with filter), demonstrating the capacity of the filter prototype to improve the environmental conditions of the surroundings. In addition, the potential energy was determined according to ASTM D4809-13, obtaining a higher heating value of up to 15.5 MJ/kg, thereby ensuring the efficient implementation of a combustion chamber with thermal storage that transfers heat to a forced-air drying system for food, replacing the use of fossil fuels in this methodology. The use of these compact drying systems involves the generation of emissions of O₂, CO, CO₂, N₂, and H₂S. Therefore, monitoring of these emissions is conducted using a gas analyser.