## 3 Results and Discussion
### Characterization of Biochar  
#### 3.4.1 SEM-EDS Analysis  
Figures 7 and 8 show the microstructures and morphologies of the biochar obtained via SEM. Figure 7a-c show the SEM images of oak chars derived from MG under different temperatures, which are 600, 800, and 1000 \({}^{\circ}\)C. The EDS analysis is shown in Table 7. The biochar exhibits a fibrous structure at 600 \({}^{\circ}\)C. The higher concentrations of C, O, Ca, and  
Figure 6: Tar component distribution from corn stalk (**a**) and oak (**b**) gasification. Mg elements suggest that calcium and magnesium carbonates are the primary compounds found in this area (Figure 7a). At 800 \({}^{\circ}\)C, the fibrous biochar disintegrates, creating a small amount of granular biochar. A decline in the concentration of element C is observed, while an increase occurs in the content of element Si (Figure 7b). This indicates that the biochar consists mainly of silicate with a small amount of carbonate. At 1000 \({}^{\circ}\)C, the fibrous nature of biochar disappears. Instead, a noticeable increase in the granular biochar structure is observed. With the increasing temperature during MG, the amount of carbon decreases from 31.67% to 3.42%, indicating a higher involvement of carbon in the gasification reaction. Figure 7d-f show the SEM images of oak chars derived from EG gasification. At 600 \({}^{\circ}\)C, the biochar shows the emergence of rod-shaped formations, but no discernible pores are present. At 800 \({}^{\circ}\)C, the biochar shows a lack of visible fibrous formations, but an increase in microscopic fibrous structures is observed, along with the emergence of distinct pore structures. At 1000 \({}^{\circ}\)C, the oak char shows a significant increase in pore quantity, resulting in a marked degradation of its fibrous structure. Under the same temperature, MG yields more small particles with an extensive pore structure. Therefore, it can be anticipated that the biochar from MG will have a more complex pore structure and a lower carbon content. Figure 8: SEM images of corn stalk chars derived from MG and EG under different temperatures: (**a**) 600 \({}^{\circ}\)C MG, (**b**) 800 \({}^{\circ}\)C MG, (**c**) 1000 \({}^{\circ}\)C MG, (**d**) 600 \({}^{\circ}\)C EG, (**e**) 800 \({}^{\circ}\)C EG, and (**f**) 1000 \({}^{\circ}\)C EG. Figure 7: SEM images of oak chars derived from MG and EG under different temperatures: (**a**) 600 \({}^{\circ}\)C MG, (**b**) 800 \({}^{\circ}\)C MG, (**c**) 1000 \({}^{\circ}\)C MG, (**d**) 600 \({}^{\circ}\)C EG, (**e**) 800 \({}^{\circ}\)C EG, and (**f**) 1000 \({}^{\circ}\)C EG. This study investigates the alterations in the microscopic morphology of corn stalk chars under various gasification temperatures and heating methods, employing identical assays. Figure 8a-c show the SEM images of corn stalk chars derived from MG under different temperatures, which are 600, 800, and 1000 \({}^{\circ}\)C. The EDS analysis is shown in Table 8. At 600 \({}^{\circ}\)C, corn stalk chars have larger particles and a more fibrous structure. At 800 \({}^{\circ}\)C, the char surface shows fewer large lumpy particles and tubular structures but an increase in microporous structures. The formation of micropores increases as the gasification temperature rises due to the Boudouard reactions. The pore structure of the corn stalk char decreases significantly at 1000 \({}^{\circ}\)C. This indicates that the char could melt and deform, while the pores would shrink and even close at a higher temperature. Figure 8d-f show the SEM images of corn stalk chars derived from EG. The corn stalk char retains its tube bundle shape at 600 \({}^{\circ}\)C. Microporous structures are more prevalent in biochar at 800 \({}^{\circ}\)C. The pore structure of biochar is significantly disrupted at 1000 \({}^{\circ}\)C.  
At the same temperature, biochar obtained from MG has a higher concentration of mesopores and macropores, leading to a more diverse pore structure.