## 2 Materials and Methods  
### Study Site, Feedstock, and Biochar Generation  
The state of Aguascalientes, Mexico ranges from 22\({}^{\circ}\)27\({}^{\prime}\) to 21\({}^{\circ}\)38\({}^{\prime}\) N and from 101\({}^{\circ}\)53\({}^{\prime}\) to 102\({}^{\circ}\)52\({}^{\prime}\) W (Figure 1) [34]. The state holds substantial untapped biomass potentials for BC generation, which could be of higher interest for the semi-desert state as BC addition to soil can increase water absorbance and water holding capacity (WHC) [35; 36; 37; 38]. Data concerning quantity and woody species composition was acquired and analyzed from the municipal composting site and the sanitary landfill. Further samples were collected from forest residues in the northern municipality of Rincon de Romos. The total identified woody biomass potential totaled up to 233,000 tons of dry matter, encompassing 11 different wood species. The collected feedstocks were used to generate four different BCs. The pyrolysis process was conducted by the use of a locally assembled Kon-Tiki flame curtain kiln at Universidad Panamericana (UP). Pyrolysis temperature ranged from 600 to 680 \({}^{\circ}\)C at the surface of the blaze. Duration of pyrolysis ranged from 3.5 to 4.5 h. Figure 1 illustrates the study related locations within the state of Aguascalientes.  
This study attempts to assess ways of biomass use for BC production under real conditions. Therefore, the collected feedstocks were not separated and distinguished into pure types, fractions, and species. This approach is substantiated because the feedstocks are found mixed-up in the forest and the collection centers and separation would be neither economically reasonable nor could a high-tech-based separation guarantee pure fractions.  
Sample 1: consisted of a mixture of 65% manchineel tree and 35% pine with average moisture of 8% for manchineel tree and 7% for pine. The branch diameter ranged from 0.5 to 8 cm for both types of wood. The collection took place in the forests of Rincon de Romos.  
Sample 2: Was collected from the municipal composting site. It was a mixture of different species of wood, which were mainly branches. The following Table 1 illustrates the composition as the biomass was piled at the composting site. The branch diameter ranged from 0.5 to 10 cm for all types of branches. The average moisture was 18%.  
Sample 3: Was collected from the municipal composting site and was a mixture of different species of wood, but was composed of much thicker trunks. The trunks were split into logs, with a diameter range from 4.5 to 12 cm in final size. Table 2 illustrates the composition of the biomass species and the percentage share applied in sample 3. The average moisture was 27%.  
Sample 4: Was also collected from the municipal composting site. Its woody composition was similar to sample 2, but the feedstock of sample 4 was chopped to grain size 0.5 to 8 cm long and 0.5 to 2 cm thick. The average moisture measured 45%.  
Figure 1: Location of three feedstock sampling sites, pyrolysis, and the laboratory site in the state of Aguascalientes, Mexico. Brown dot: Municipality of Rincon de Romos—“Sierra Fria”; yellow dot: Sanitary Landfill—“San Nicolas”; green dot: Green Area—”Parque Mexico”; Red dot: Universidad Panamericana—“Kon-Tiki flame curtain kiln”; blue dot: Universidad Autónoma de Aguascalientes—“Laboratory”.