Enhancing energy content of hydrochar produced by hydrothermal carbonization of biomass through addition of grease waste

Abstract Fat, oil, and grease waste can cause sanitary sewer overflows, property flooding, and sewage contamination of water bodies. Innovative technologies could significantly improve the potential for waste utilization. The hydrothermal carbonization (HTC) process was employed to produce hydrochar from mixtures of grease and biomass such as pineapple peel, coconut husk, rice husk, and coffee ground. Three phases of the product implicated in the HTC process were analyzed. Hydrochar, a solid product, was found to have a higher energy content than the raw biomass. The liquid product contained low grease concentrations. Toxic hydrocarbon gases were detected in the produced gas. The energy contents of the produced hydrochar from the mixtures were increased by approximately 30–40% with the addition of grease. Temperature had a considerable impact on the energy content of the produced hydrochar, but not the reaction time. To achieve a high energy content, the optimum process conditions for hydrochar production from each type of mixture were recommended.