Effects of Operating Parameters on the Higher Heating Value of Kitchen Waste during Hydrothermal Carbonization

Abstract

Hydrothermal carbonization (HTC) is a promising waste to energy technology for conversion of organic wastes with high water contents. There have been relatively few studies focused on evaluating the HTC of solid waste (SW). The studies have provided valuable information regarding HTC feasibility and potential environmental benefits. However, they lack the data necessary to understand how carbonization product composition and reaction extent change with the variation of operating parameter. This study sought to characterize kitchen waste from a university restaurant, to assess the impact of operating parameters on hydro-char and evaluate its potential as a solid fuel. The methodology for characterization was based on proximate analysis, ultimate analysis and calorific value. A ratio of dry sample to water of 1:9 was used to make a wet sample and stirred at 180 rpm in a thermal reactor under controlled HTC conditions. The results from proximate analysis revealed that moisture content, volatile matter, ash content and fixed carbon content were 9.6%, 65.1%, 13.6%, and 11.9% respectively. The ultimate analysis showed that carbon, hydrogen, nitrogen, Sulphur and oxygen were 48.8, 0.5, 0.4, 0.5 and 45.3% respectively. Mass yield of hydro-char decreased for all samples with increasing HTC reaction temperature. ANOVA confirmed the adequacy of the model, yielding R2 and adjusted R2 values of 0.8630 and 0.7398, respectively with a P value of 0.003 and F-value of 7.00. The high heating value, ultimate analysis and proximate analysis suggested that the hydro char from kitchen waste can potentially be utilized as a solid fuel.