Chemical Composition of Birch Wood Slow Pyrolysis Products

Birch distillate, a byproduct in charcoal production, has found to be a promising source for biological pesticides. The aim of this paper was to determine the yields and chemical compositions of liquid and gaseous products from the slow pyrolysis of birch hardwood, which is needed in the commercialization process of the byproduct. Test runs were performed using three different retorts. Distillates, aqueous phases, settled tars, wood vinegars, and gases were analyzed with an analytical scheme developed. About 95 wt % of the aqueous phases was analyzed. The main compounds were water, acetic acid, methanol, hydroxypropanone, furfurals, acetone, and syringol, catechol, and phenol derivatives, and sugarlike compounds. The tar and polycyclic aromatic hydrocarbons contents of aqueous phases were low, or they could be lowered by simple water addition when needed. On the basis of compositions, birch wood vinegars have potential to be used for example as biodegradable pesticides, to replace synthetic pesticides. At low temperatures, formed tar-free distillates (predistillates) can be separated from the main distillate and utilized. Because of their low pH and high organic load, they cannot be disposed to the environment without treatment. The amount of polycyclic aromatic hydrocarbons in the tars has to be considered, and therefore, the tars Were suggested to be utilized mainly as energy. The gases are promising to be utilized, in addition to the process itself, for other energy needs. The differences obtained for the products of different processes were mainly between batch and continuous processes. The detailed compositions of the products may be exploited by enterprises and authorities for registration purposes in the commercialization process.