Production of biocoal from wastewater sludge and sugarcane bagasse using hydrothermal carbonization

Abstract

AbstractThe growing demand for fuel in South Africa coupled with the depletion of fossil fuel reserves demonstrates the need for alternative energy sources. A renewable resource such as biomass can be optimized as an energy source. Wastewater sludge and bagasse have the energy potential to produce high calorific value biocoal; this will contribute to the supply of energy in South Africa. The synthesis of biocoal from wastewater sludge and bagasse through an artificial synthetic coal production process, i.e. hydrothermal carbonization, is preferred over other thermal conversion techniques as hydrothermal carbonization is capable of handling feed having a high (75–90%) moisture content. In this study, wastewater sludge and sugarcane bagasse were subjected to hydrothermal carbonization, and the effect of temperature was explored at 180, 210, 240 and 260°C. Variation of the ratio of dry sludge to bagasse of 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 and the composition of solid to liquid (solid loading wt%) of 1:10, 2:10, 3:10 and 4:10 (SB:H2O) corresponding to 9.09, 16.67, 23.08 and 28.57 wt% loading was investigated. The results obtained in this study reveal that solid loading, temperature, biomass type and ratio variation had a substantial impact on the yield and calorific value of the biocoal produced. The highest biocoal yield of 23.36 wt% was achieved at 210°C and derived from sludge/bagasse with a sludge content of 20%. Across all of the runs, the highest calorific value of 20.21 MJ kg−1 was achieved at 260°C when pure bagasse was employed (0% sludge content). © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.