Production and characterization of two fractions of pyrolysis liquid from agricultural and wood residues

Liquids obtained by fractional condensation of pyrolysis vapors from two types of lignocellulosic biomass, namely Jerusalem artichoke stalk (high cellulose and ash contents) and white birch bark (high lignin and extractive contents), were compared. Using two condensers connected in series, a dark oily fraction rich in phenolic compounds and sugar derivatives was obtained at 90 °C (respectively, 14% of total polyphenols and 11% of total carbohydrates for the oily fraction from the agricultural stalk) followed by aqueous fraction at 0 °C. Stalk yielded a homogeneous oily fraction whereas the bark oily liquid was heterogeneous, due possibly to lignin pyrolysis products. Both yielded clear orange aqueous fractions having a chemical composition close to wood vinegar, > 60% water, and high concentrations of acetic acid, with also a significant content of polyphenols, around 5%. This study showed that fractional condensation could be a vital tool in pyrolysis-based biorefinery producing an oily (application as an energy source or as a chemical feedstock) and an aqueous fraction (applications as biocide or biostimulation in agriculture) by pyrolysis of vastly different lignocellulosic biomasses.