Torrefaction Process of Needles, Cones and Bark of Spruce (Picea Abies (L.) Karst) and Pine (Pinus Sylvestris L.)

Abstract

The actual problems related with the depletion of fossil resources and the accentuated increase of global warming requires rapid shift to renewable and eco-friendly alternatives. Biomass forestry residues are valuable candidates that can be used as sustainable resources. Torrefaction is a mild thermal treatment that can convert biomass into value-added liquid and solid products. Here we performed torrefaction at 250 �C of needles, cones and bark from spruce and pine, as representative coniferous species in Romanian Carpathians. The elemental analysis of solid materials was performed and the calculated O/C and H/C atomic ratios showed that torrefaction placed the solid materials in the region of coals, close to the origin of the Van Krevelen diagram. The calorific values were improved, leading to higher energy density. The energy yield was close to the unit, indicating that torrefaction is a highly efficient process. The liquid products had complex composition, with compounds coming from the compositional and structural changes in the forestry residues. Terpenes are the dominating compounds from volatile extractives. Furans, from which furfural and 5-methylfurfural were the main compounds produced from degradation of hemicelluloses, while phenol derivatives were produced from lignin. Exploratory data analysis revealed diferences between samples from spruce and pine but also between needles, cones and bark.