Comparison of Lignin, Macroalgae, Wood, and Straw Fast Pyrolysis

A fast pyrolysis study on lignin and macroalgae (nonconventional biomass) and wood and straw (conventional biomass) were carried out in a pyrolysis centrifugal reactor at pyrolysis temperature of 550 °C. The product distributions and energy recoveries were measured and compared among these biomasses. The fast pyrolysis of macroalgae showed a promising result with a bio-oil yield of 65 wt % dry ash free basis (daf) and 76% energy recovery in the bio-oil while the lignin fast pyrolysis provides a bio-oil yield of 47 wt % daf and energy recovery in bio-oil of 45%. The physiochemical properties of the bio-oils were characterized with respect to higher heating value (HHV), molecular mass distribution, viscosity, pH, density, thermal behaviors, elemental concentrations, phase separation, and aging. The lignin and macroalgae oil properties were different compared to those of the wood and straw oils with respect to carbon and oxygen contents, HHV, thermal behaviors, and mean molecular weight. The HHV of wood, straw, lignin, and algae oils were 24.0, 23.7, 29.7, and 25.7 MJ/kg db, respectively. The distributions of metals, Cl and S in char and bio-oil were investigated for the biomasses. Almost all the metals (Al, Ca, Fe, K, Mg, Na, P, and Si) were contained in the chars at the pyrolysis temperature of 550 °C. The char properties were characterized, and their potential applications are discussed.