Caracterização físico-química de extrato pirolenhoso de carvão vegetal e sua aplicação na miniestaquia de Eucalyptus urophylla

Abstract

The pyroligneous extract (PE) from Eucalyptus spp., a byproduct of wood carbonization from reforestation, has gained prominence in biological activation, plant development, and growth. Derived from sustainable charcoal production systems with low pollutant gas emissions, the recovered PE presents a complex composition and variable physicochemical properties, posing challenges for its efficient production and application. This study aimed to investigate PE by evaluating its physicochemical properties under the influence of collection temperature and assessing its efficacy in rooting mini-cuttings of a recalcitrant clone of Eucalyptus urophylla S.T. Blake, as an alternative application in the forestry sector. PE collections were performed using two distinct systems: semi-open carbonization furnace-kilns with manual oxygen control, comprising four treatments, and the Carboval® reactor with automated oxygen-free carbonization. The treatments were defined according to PE collected at temperature ranges: Furnace-kiln T1 (60–170°C), T2 (171–270°C), T3 (271–350°C), T4 (351–400°C), and the Carboval reactor T5 (120–460°C). PE samples were subjected to physicochemical and compositional analyses using parametric and analytical methods. The results allowed the definition of biochemical profiles, determination of properties, and statistical analyses, revealing the influence of wood carbonization temperature on the behavior of organic chemical composition and physicochemical characteristics of PE. To evaluate PE as a rooting bioproduct and its efficacy in rooting, pyroligneous extracts were tested by analyzing the response effect of a single dose (2.5% v/v) and the influence of biochemical profiles across treatments: Control (T0): No PE application; (T1, T2, T3): PE with a biochemical predominance of carboxylic acids; and (T4, T5): PE with a biochemical predominance of phenolic compounds, correlating with morphophysiological and histological parameters of induction and enhanced roots. The results evidenced that PE characteristics are modulated by organic chemical composition, varying relatively across thermal ranges, highlighting two main biochemical groups (Carboxylic acids and Phenolics). Thus, PE with a predominantly carboxylic acid profile, particularly acetic acid, was obtained at lower temperatures, collected within the temperature ranges of treatments T1 (60–170 °C), T2 (171–270 °C), and T3 (271–350 °C). Conversely, PE obtained at temperatures above 350 °C demonstrated a predominance of phenolic compounds, corresponding to treatments T4 (351–400 °C) and the Carboval reactor T5 (120–460 °C). Intermediate temperatures around 350 °C served as reference points for obtaining PE rich in bioactive compounds of interest. The collection of PE within specific temperature ranges during the carbonization of Eucalyptus wood was essential for optimizing its production, enabling targeted application and physicochemical properties differing across the evaluated thermal ranges. PE with a predominantly phenolic profile (T5) proved to be more effective in overcoming recalcitrance in rooting mini-cuttings of the Eucalyptus urophylla S.T. Blake clone, also in addition to promoting higher rooting percentages and better-quality roots. These findings reinforce the potential of phenolic PE as a bioproduct, adding value to the byproducts of the charcoal production chain.