Food Waste Biomass-Derived Hydrochar by Hydrothermal Carbonization for Solid Biofuel Production

Energy catalyzes economic development, with research into energy technologies essential for identifying alternatives that could mitigate against the reliance on fossil energy and its aggravating environmental impacts. This study explored the conversion of food waste (FW) biomass into hydrochar achieved via hydrothermal carbonization (HTC) technology. The research focused on evaluating the merits and demerits of using mixed FW feedstock, especially rice, potatoes, vegetables, and/or animal byproducts such as meat and fish at varying water-to-biomass ratios and through the implementation of water recirculation in the HTC process. This approach aimed to decrease water consumption while assessing its impact on the fuel characteristics of the resultant hydrochar. The hydrochar produced demonstrated an enhanced carbon content, which is conducive to combustion, while also exhibiting improved fuel properties such as elevated heating values, improved energy densities, and reduced volatile components. Conditions exceeding 200°C, with a reaction time of 6 h, were found to be sufficient to attain an average carbon content of above 70% and a heating value of around 30 MJ/kg. Moreover, decreasing the water-to-biomass ratio enabled a reduction in initial water usage by up to 50%, without significantly impairing the carbon content and fuel attributes of the hydrochar. Thermogravimetric analysis (TGA) indicated a comparatively elevated combustion temperature of 600°C for the hydrochar generated at an HTC temperature of 220°C, which corresponded with a substantial increase in the carbon content of hydrochar up to 70.65% from initial 48% in the parent biomass. Consequently, the hydrochar generated from FW under different HTC reaction conditions, including water volume reduction and recirculation, demonstrated the potential for minimal water consumption. This method represents a promising strategy for enhancing HTC as a renewable energy technology.