Production of Hydrochar from Domestic Kitchen Waste using Hydrothermal Carbonization

Abstract

Organic waste from household at present is converted to biogas and manure through anaerobic digestion process. Often the digestion process is slow and the obtained products need additional processing further delaying utilization of waste. Hydrothermal carbonization (HTC) is a novel thermochemical process that converts domestic wet waste to useful solid fuel called hydrochar. HTC is a fast process needing only few hours and the products are sterile. This means, the produced hydrochar can be handled safely by waste handlers (paurakarmikas). HTC process involves processing the wet waste in a reactor at temperatures exceeding 180 °C for several hours in the presence of water.

The present work involves application of HTC technique to convert the household wet waste to hydrochar. A batch reactor was designed and fabricated to withstand temperatures above 250 °C, and pressure of about 1.5 MPa. The experiment involves heating the reactor and its contents to temperatures of 200 °C for up to 2.5 hours in an oven. The hydrochar thus obtained was checked for its microstructure and composition using SEM and XEDS analyses. The results from the microstructure analysis shows that the food fibres are not completely broken down at the experimental conditions. Overall, the hydrochar had porous structure with pore diameters in the range of 10 - 100 µm. The XEDS analysis shows the presence of Nitrogen and Oxygen along with Carbon, which indicates hydrochar as an alternative fuel and can lead to safe disposal of wet waste.