(271b) Hydrothermal Carbonization of Wet Biomass Materials for the Production of Hydrochar

Organic waste is a major component of landfills, which is the largest source of methane emission in the USA. From harvesting to consumption, excluding the non-edible parts, 30-40% of the food is wasted, equaling more than 35 million tons per year or approximately 240 pounds of food per year per person. Finding ways to utilize this wet organic waste into useful products will be desirable from both economic and environmental sustainability points of view.

Villanova University and Gray Brothers-Somax Environmental Company are working together in developing a comprehensive biorefinery system involving multiple conversion process technologies, specifically anaerobic digestion and thermochemical processes, for utilizing municipal and agricultural solid waste into various valuable bio-based products. One conversion process technology being studied is the hydrothermal carbonization (HTC) process. HTC is a thermochemical process that converts wet biomass materials to a coal-like product. Under sub-critical conditions, water in the HTC reactor stays in liquid form and acts as a reaction medium to promote the breakdown and cleavage of chemical bonds in the solid biomass. The absence of liquid-to-vapor phase change of the water makes the process significantly less energy intensive compared to a process that involves water vaporization or drying. The temperature range for HTC is from 180-240^oC producing solid hydrochar as the main product.

The focus of this research was to evaluate the effects of feedstock and HTC process parameters on the yields and physiochemical properties of hydrochar products. HTC reaction temperature and retention time were the major parameters that were varied. Retention times varied from thirty minutes to two hours and the temperature range was focused between 180C and 240^oC. Nine different food groups and other biomasses were used as feedstocks for the HTC process, which include: vegetable proteins, mixed vegetables, carbohydrates, dairy, fruits (and fruit waste), animal proteins, brown grease, anaerobic digestor seed, and a mixed food waste.

Various analytical and characterization testing will be conducted on the liquid, solid, and gas products of the HTC process. The characterization techniques will include CHNOS elemental analysis, approximate analysis (TGA), specific surface area, porosity, heating value, and microstructure (SEM analysis) of the hydrochar products. The liquid and gas analysis will be performed by using gas chromatography techniques. Results from this study will be analyzed to determine the potential optimum process conditions for the HTC process for different organic material feedstocks.

*Contact: Dr. Justinus Satrio (justinus.satrio@villanova.edu)