## 2 Materials and Methods  
Biochar was produced from three types of waste biomass: 12-year-old _Pinus pinster_ from a failure plantation (due to unsuitable silviculture conditions), 5-year-old _Eucalyptus globulus_ affected by a fire and weevil infestation, and biomass from a mass of invasive _A. dealbeta_. Figures 1-3 show the original biomass material in forestry (a), processed waste material (b), and final biochar (c). The study thus involves two hardwoods and one softwood, comprising lignocellulosic biomass from widely distributed trees. The three primary components of these lignocellulosic biomasses are cellulose, hemicellulose, and lignin [27], together with inorganic chemicals and organic extractives, as well as a significant amount of free and bound water. Figure 1: _P. pinster_ (**a**) waste material in the forestry, (**b**) crushed material, and (**c**) final biochar. Figure 2: _E. globulus_ (**a**) waste material in the forestry, (**b**) crushed material, and (**c**) final biochar. Biomass and biochars exhibit a multitude of physical, chemical, and mechanical characteristics, which vary depending on the raw material and pyrolysis conditions, making their characterization essential [28]. For the characterization of the biomass and biochar, different standards of solid biofuels were used to prepare the material [29] and determinate the following: moisture content (%) [30; 31], density (kg/m\({}^{3}\)) [32; 33; 34], calorific value (kJ/kg) [35], volatile matter (%) [36], ash content (%) [37], fixed carbon content (%), total carbon, hydrogen, and nitrogen content (%) [38], and principal major and minor elements of composition (%) [39; 40; 41]. The biochar yield was determined as the ratio of the prepared biochar weight in relation to the weight of the initial biomass subjected to pyrolysis, according to Equation (1). \[\text{Biochar yield}=(\text{w2/w1})\times 100 \tag{1}\]  
where w1 is the weight of the biomass at the moisture content on a wet base before pyrolysis and w2 is the biochar weight at the end of the thermal transformation process. Fixed carbon is the solid carbon in the biomass and biochar that remains in the pyrolysis process after devolatilization. It is determined from the following Equation (2). \[\text{Fixed Carbon}=1-\text{Vd}-\text{Ad} \tag{2}\]  
where Vd and Ad were the volatile matter content and the percentage of ashes on a dry basis. In relation to the thermal process employed for biomass transformation and biochar production, Figure 4 shows the conditions of the slow pyrolysis process, divided into three phases. The first phase involves water content evaporation and biomass heating, with an increase in the temperature at a rate close to 4.5 \({}^{\circ}\)C/min for the first 40 min, reaching a maximum temperature of 540 \({}^{\circ}\)C over the next 90 min. In the second phase, pyrolysis occurs with the emission of syngas, with the temperature ranging between 540 and 480 \({}^{\circ}\)C for the subsequent 255 min inside the pyrolysis chamber, considering a long residence time [13]. Finally, there is a third phase of cooling, during which the high residual temperature decreases to room temperature (15 \({}^{\circ}\)C) over a span of 15 h.  
The reactor employed operates at a semi-industrial scale conducted by the research group. Figure 5 shows the exterior (a) and interior view (b) of the reactor, along with a real image of the installed unit (c). Figure 5b shows the double chamber: \"chamber 1\" where high temperatures are generated using biomass, with a volume of 0.17 m\({}^{3}\) and outlet chimney for gas and smoke; and \"chamber 2\", contained inside chamber 1, where the biomass is transformed into biochar, with a capacity of 0.10 m\({}^{3}\), and is sealed from the outside with a  
Figure 3: _A. dealData_ (**a**) waste material in the forestry, (**b**) crushed material, and (**c**) final biochar. 5 mm gas outlet hole.