Production of biochars from textile fibres through torrefaction and their characterisation

Abstract

In this study, the utilization of textile fibres as energy feedstock in the form of biochar was investigated depending on the fibre type. The biochars were produced from waste natural and synthetic fibres and its blends. For this purpose, different types of textile fibres (cotton, viscose, polyester, acrylic) and their blends (cotton/polyester, acrylic/wool, acrylic/polyester, acrylic/viscose) were torrefied at temperatures between 300 and 400 °C. The effects of torrefaction temperature and fibre type on biochar yield and biochar properties (fuel properties, morphological and structural properties and combustion characteristics) were investigated. The results showed that the temperature had a significant effect on biochar yield whereas the fibre type was the only significant factor on energy densification ratio and biochar properties. The torrefaction of tested fibres and blends resulted in an energy-intensive solid fuel, having a negligible amount of ash and sulphur. Although torrefied acrylic based textile fibres had similar H/C and O/C ratios to bituminous coal, it was concluded that high nitrogen contents will limit their usage as fuel. Overally, this study showed that torrefaction of cotton and cotton/polyester textile wastes is a promising process for the production of a solid fuel, which can be used as a substitute fuel in coal/waste co-firing systems.