Torrefied materials derived from waste vegetable biomass

Abstract

Torrefied materials produced from agricultural waste is regarded as one of the most efficient renewable energy source. By recycling the waste materials through optimized torrefaction process, coal like material can be produced. The raw materials are heated up in a sealed, oxygenless environment at 300 °C. At this temperature, many of the volatiles in the material begin to decompose and part of the sappy lignin that binds the material together breaks down and vaporizes. This study focuses on exploring to convert agricultural waste to torrefied material, the biocoal through fast and slow conversion process. The waste vegetable biomass material selected for this study were waste cauliflower, lettuce and coriander. Proximate, ultimate and TGA analysis were done after drying and pulverizing the material. The powdered samples were pelleted and their calorific values and yield were recorded. Torrefaction was conducted under 300 °C for a given residence time at a fast and slow heating rate. The torrefied material, especially from coriander residue gave the highest yield and calorific value under slow torrefaction process of 46.6% and 16.45 MJ/kg respectively. The high carbon content in biocoal makes potential coal substitute for use in thermal conversion systems. The material is densified after torrefication, the remaining lignin in the product, requires no binding agent to make the pellets, briquettes and bricks for co-firing applications.