The effect of the hydrothermal carbonization process on palm oil empty fruit bunch

Investigations of biomass conversion technologies and processes have been carried out intensively for the past two decades due to the reduction in the availability of landfill, stricter regulations, and increasing awareness of the problem. In this study we have concentrated on a wet-base biomass, in particular a waste stream from the commercial production of palm oil, empty fruit bunch (EFB). This has been converted through a hydrothermal carbonization process (HTC), where lignocellulosic material was converted in a low temperature and pressure environment to a product of increased carbon content offering the prospect of a material with a higher commercial value from an abundant waste stream. A purpose built pressure vessel was used in the presence of excess water at relatively low temperatures (180–220 °C) and saturated water pressures (1–22 MPa). The chemical and physical characteristics of the products were confirmed using elemental analysis, calorific value, SEM, FTIR and GCMS. The carbon value recorded a decrease of the O/C ratio of raw EFB = 0.85 to a HTC processed EFB of 0.55. The surface morphology obtained from SEM showed minimal structural modification of the material although small pores (10–13 μm) were seen on the surface of the HTC processed material. This suggests a processing route that preserves the existing carbohydrate structure whilst increasing its carbon content, which offers a route to complex carbon-rich materials based upon naturally grown carbohydrate materials.

► The empty fruit bunch was converted into carbon-rich material.
► The hydrothermal carbonization process with no catalyst was carried out.
► The operating condition varies from temperature, 180, 200 and 220 °C for 2–24 h
► The characteristics of biocarbon changes at higher temperature.
► Carbon-rich products were obtained.