An analysis of effect of temperature and pressure on bio pellets physicochemical properties

Organic municipal waste offers an opportunity for a renewable and clean source of energy through the production of bio pellets, for larger domestic thermal use, providing an attractive waste management initiative. In this study, municipal bio waste was shredded to particle sizes of 40 mm and pelletized at 200–400 °C for 10 min at a pressure of 150–450 MPa. The bio pellets’ physicochemical parameters such as moisture content, ash content, volatile matter, fixed carbon, density and the calorific value were measured using standard methods. The Analysis of variance and regression analysis in Matlab R2024b was used to determine the effect of temperature and pressure on the bio pellets physicochemical characteristics. The bio pellets had an average moisture content of 1–3–1.6 %, ash content of 4.1–8.1 %, volatile matter of 6.7–26.1 %, fixed carbon content of 60.7–88.0 % and density of 0.47–0.79 kg/cm³. The calorific value of the bio pellets ranged from 13.9–19.9 MJ/kg making it ideal for thermal energy purposes. An analysis of increased processing temperature and pressure of the bio pellets using a 2-way Analysis of variance (ANOVA) and regression analysis in MATLAB R2024b software at a p-value of 0.05 indicated that increase in these parameters resulted in decreased moisture content, ash content, volatile matter of the bio pellets. Consequently, using the same analysis, an increase in temperature and pressure resulted in increased fixed carbon content, density and calorific value of the pellets. The regression analysis and the experimental data had average R² values of 0.9.