Municipal solid waste (MSW) is a complex problem in major cities in Indonesia that has not been resolved. MSW is currently only collected and disposed to final landfill. On the other hand, national energy security is also an issue to be solved. Utilization of MSW, which is dominated by organic waste, as solid fuel can be a solution for both problems. This paper discusses an experimental study on utilization of organic waste as renewable solid fuel using a wet torrefaction process. Four types of samples were chosen to represent the four types of organic waste in MSW with the highest mass fraction found in a field survey: leaf litter, food waste, vegetable waste and fruit waste. Each sample was treated with wet torrefaction under four conditions: 150, 175, 200 and 225 degrees C with holding time 30 minutes. The experimental results showed that the optimum wet torrefaction temperature for mixed organic waste is between 200 and 225 degrees C, which is predicted to produce a solid product with a heating value (db) of 23.22-24.44 MJ/kg, volatile matter content of 61.18-66.00%, fixed carbon content of 26.04-31.35%, ash content of 7.47-7.96%, and energy yield equal to 58%. A higher operating temperature will increase the calorific value, followed by a decrease in mass yield as a consequence of the process severity degree. However, food waste torrefaction showed different characterisics: the increase in calorific value was followed by an increase in mass yield. This is unique and different from the results of wet torrefaction on other organic wastes.
