Utilizing Urban Organic Wastes Via Hydrothermal Carbonization Process for Energy Production

Organic waste is a major component of landfills, which is the largest source of methane emissions in the world. In the USA, on food waste alone, 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 thermochemical-based process, namely hydrothermal carbonization (HTC), for converting wet organic wastes in urban communities, specifically food wastes and sewage sludge, into coal-like product called hydrocar. 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 organic solids. 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, such as incineration or gasification. The temperature range for HTC is from 180-240^oC producing solid hydrochar as the main product.

The focus of the present study is to evaluate the effects of feedstock and HTC process parameters on the yields and physiochemical properties of hydrocar products and obtain the optimal process conditions which will used for scale-up design of the HTC reactor system.