## 2 Materials and Methods
### Determination of Briquette Quality  
Particle density was calculated immediately after briquette production and 7 days later, after reaching hygroscopic balance in a conditioning room at 20 \({}^{\circ}\)C and 60% relative humidity. For the above, the briquettes were weighed and measured (diameter and length) with a digital caliper; the particle density calculation consisted of dividing the total weight of the briquette by its volume. Using particle density data from the briquettes immediately after manufacture and after conditioning, we calculated the volumetric swelling (%) of the briquettes with Equation (1) [29]:  
\[EXP=[(Vol_{2}-Vol_{1})/Vol_{1}]\times 100 \tag{1}\]  
where \(EXP\) is the volumetric swelling of briquettes (%), \(Vol_{1}\) is the volume of the briquette immediately after manufacture (cm\({}^{3}\)), and \(Vol_{2}\) is the volume of the briquette 7 days after manufacture (cm\({}^{3}\)). Compression resistance was obtained by applying a load perpendicular to the briquette shaft with an Instron 300 DX universal machine following the procedure established by [PERSON] [30] and the standard ASTM D 143-83 [31]. For this test, briquettes remained in the conditioning room until the time of the test (7 days). Briquettes were measured for length at 3 points, then placed horizontally on the bottom steel plate of the \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Treatment with Sample**} & \multicolumn{3}{c}{**Sawdust Size**} \\ \cline{2-4}  & **Large (\%)** & **Medium (\%)** & **Small (\%)** \\ \hline T0 & 12 & 71 & 17 \\ T1 & 100 & 0 & 0 \\ T2 & 0 & 100 & 0 \\ T3 & 0 & 0 & 100 \\ T4 & 33 & 33 & 33 \\ T5 & 67 & 33 & 0 \\ T6 & 67 & 0 & 33 \\ T7 & 0 & 67 & 33 \\ T8 & 0 & 33 & 67 \\ T9 & 33 & 67 & 0 \\ T10 & 33 & 0 & 67 \\ \hline \hline \end{tabular}  
Ten briquettes of each treatment were produced using 40 g of sawdust introduced into a LIPPEL laboratory briquette producer and pressurized at 20 Mpa for 5 min and 80 \({}^{\circ}\)C. Physical and chemical properties of the briquettes are presented in Table 2.  
\end{table} 
Table 1: Percentage of each sawdust particle size used in each treatment. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{ \begin{tabular}{c} Treatment \\ **with Sample** \\ \end{tabular}  } & \multicolumn{3}{c}{**Physical Properties (Size)**} & \multicolumn{3}{c}{**Proximate Analysis Values**} \\ \cline{2-7}  & **Weight (g)** & \begin{tabular}{c} **Diameter** \\ **(mm)** \\ \end{tabular}  & **Length (mm)** & **Moisture** & \ \begin{tabular}{c} **Volatile** \\ **Content (\%)** \\ \end{tabular}  & **Ash (\%)** & \begin{tabular}{c} **Fixed** \\ **Carbon (\%)** \\ \end{tabular}  \\ \hline T0 & 39.79 (0.08) & 33.23 (0.08) & 46.06 (0.34) & 5.12 (0.01) & 82.86 (0.01) & 0.56 (0.02) & 11.46 (0.01) \\ T1 & 39.5 (0.21) & 33.46 (0.11) &  
universal machine. A compression load was applied at a constant speed of 0.305 mm min\({}^{-1}\), and this compression force (maximum load point, N) was registered at the time of rupture of the briquette. Five briquettes from each treatment were tested and the compression resistance (N mm\({}^{-1}\)) was obtained with Equation (2):  
\[C=(3\times F)/(L_{1}+L_{2}+L_{3}) \tag{2}\]  
where \(C\) is the compression resistance (N mm\({}^{-1}\)), 3 is a constant, \(F\) is the force at the fracture point (N), and \(L_{1}\), \(L_{2}\), and \(L_{3}\) are the respective lengths of the briquette measured at 3 points. The impact resistance index (IRI) was calculated using the methodology described in ASTM D440-86 [32], where each briquette is vertically oriented and dropped twice from a height of 2 m. The number of pieces in which it fragmented was registered. Finally, the impact resistance index was calculated as described by [PERSON] [33] with Equation (3):  
\[IRI=(100\times N)/n \tag{3}\]  
where \(IRI\) is the impact resistance index, \(N\) is the number of drops (2), and \(n\) is the number of fragments after \(N\) drops.