Hydrothermal Carbonization of Switchgrass for Biochar Production

Hydrothermal treatment, an environmental friendly technology, provides a novel method for the utilization of biomass. The hydrothermal carbonization (HTC) process, a traditional but recently revived method, presents superior characteristics that make it a promising route of wide potential application for converting biomass to biochar. In this work, switchgrass, a major energy crop, was processed by HTC method in a batch reactor. The effect of temperature (200-230°C), reaction time (1-4 hrs), and pressure (14-276 bar) are examined. The obtained biochar was characterized for molecular structure by infra-red spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The heating value of biochar were analyzed using a bomb calorimeter and results were compared with the theoretical heating value determined based on elemental analysis. With the increased severity, the lignocellulosic structure of switchgrass is broken and comparatively less fibrous biochar having a high energy density is obtained. The FTIR and SEM analyses show that biochar contained rich new functions groups. The results demonstrate that the HTC process can provide a promising route for carbonaceous functional materials and higher energy density fuel for use in a variety of applications.