Fuel property enhancement of lignocellulosic and nonlignocellulosic biomass through torrefaction

Torrefaction is a mild thermal pretreatment process at temperatures of 200—300 °C in a minimum oxygen environment at a reasonable residence time that enhances the thermochemical properties of biomass in terms of energy density, hydrophobicity, and grindability. Present study uses different samples of biomass: oats from the agricultural family, willow from the woody family, and poultry litter from the non-lignocellulosic family of Ontario. They analyze different fuel characteristics of the torrefied biomass at different temperatures (200—300 °C), residence times (15–45 min), and oxygen concentrations (0–2.4 %) in a macro-TGA. From the experiment, torrefied products have up to 42 % higher heating value than raw biomass. The heating value of 24 MJ/kg for oats, 22 MJ/kg for willow, and 12 MJ/kg for poultry litter are found after torrefaction. Mass yield varies from 42 to 91 %, whereas energy yield varies from 61 to 89 % at different operating temperatures and residence times. Oats show the fastest mass and energy yield, whereas poultry litter shows the least. For hydrophobicity and moisture uptake, the optimum temperature is found to be at 285 °C for willow, 270 °C for oats, and 275 °C for poultry litter at a 45-min residence time. It is observed that all products show hydrophobic characteristics and remain unaffected from biodegradation when they are immersed in water after torrefaction.