(261g) Hydrothermal Carbonization of FOOD Wastes from LOCAL Eatery

Since 2014, it has been estimated that the world has produced nearly 2 billion tons of garbage also known as municipal solid waste (MSW) and it is further projected that this generated waste will be increased by nearly five times by 2050 due to large economic and urban growth of developing countries. In the U.S, a typical garbage disposal fee of $20-50 per month, varies from county-to-county, applies to every household. Garbage contains mainly food waste and the composition can add up to 70 %. Except from some cases, where food waste garbage has been composted or used as animal feed, it ends up in a landfill, where it contributes to environmental pollution via greenhouse gases (mainly methane and carbon dioxide). Large metropolitan cities like Los Angeles, New York etc. are facing serious waste disposal challenges with the lack of adequate lands. Although garbage has huge potential for energy production, converting garbage to energy in both efficiently and economically is yet to be discovered.

Hydrothermal carbonization (HTC) is an exceptional treatment process for biofuel production, as residual water is the reaction media for HTC. Therefore, the wet biomass need not be dried prior to the HTC. Subcritical water at around 200-260 °C has the highest ionic constant, which means it is quite reactive. As a result, within 5 minutes of reaction with biomass, solid-hydrophobic biofuel is formed along with liquid and gas byproducts. The solid product, also called hydrochar, is quite hydrophobic, friable, and more importantly energy dense; an increase in energy density means that less mass is required to produce the same amount of energy. Pelletization of the hydrochar allows for more energy densification as well as better storage of the fuel. Moreover, the exothermic HTC reaction ensures the minimum energy input for biofuel production. Researchers around the world have been developing HTC over the last decade for woody biomass and agricultural residues.

The main goal of this study is to apply HTC to local eatery wastes for producing clean and sustainable energy. Waste disposal issues will be automatically resolved with this proposed process. In this study, a 2L batch Parr reactor was used for HTC for recycle, compostable, and trash bins wastes at 200, 230, and 260 °C at their water saturation pressure. Solid hydrochar, HTC process liquid, and gaseous products were analyzed for their physicochemical properties. Based on batch HTC results, a simple techno-economic analysis was performed using ChemCAD 6.0 simulation. The simulation results indicate that higher HTC temperature is favorable for solid fuel production, however, such high-pressure and high-temperature system requires high capital investment.