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Pine sawdust biofuel: Quality and temperature optimization

to reduced relaxed density. This phenomenon likely
resulted from insufficient lignin softening and bonding
under non-uniform temperature conditions.
A moderately negative correlation (ρ = −0.500,
p=0.011) exists between MSD and impact resistance,
attributable to structural inhomogeneity caused by
uneven heat distribution. However, the non-significant
relationship with relaxation ratio (ρ = −0.199, p=0.339)
suggests minimal MSD influence, implying dominant
effects from other factors.
Temperature field uniformity critically affects
densified biofuel quality. Uniform heating (low MSD)
promotes homogeneous lignin activation, enhancing
interparticle bonding and consequently improving both
Figure 5. Response surface plot for forming pressure relaxed density and impact resistance.
and heating temperature
5. Conclusion
To verify the reliability of the conclusions drawn from
the response surface analysis and to assess the influence of This study developed an innovative pine sawdust
temperature field uniformity on densified biofuel quality, densification methodology based on temperature
a multiobjective optimization was performed using field optimization, providing an effective solution
the Design-Expert 13.0 software on the experimental for forestry waste valorization. The investigation
data from Table 1. The optimal parameter combination demonstrated that forming pressure, moisture content,
was predicted as follows: forming pressure = 10.0003 and heating temperature critically influence pellet
MPa, moisture content = 10%, binder addition ratio = quality. Statistical analysis revealed that forming
3.16532%, and heating temperature = 190℃, which pressure, moisture content, heating temperature, and
aligns with the response surface plots. their interactions exhibited extremely significant effects
Validation experiments confirmed that under these (p<0.01) on both relaxed density and impact resistance,
optimal conditions, the pellets exhibited a relaxed whereas heating temperature and its interaction with
density of 0.964 g/cm , a relaxation ratio of 1.076, pressure significantly affected the relaxation ratio. The
3
and an impact resistance of 98.78%. This parameter relative importance of factors affecting temperature
combination ensures that the pellets achieve maximized MSD follows the hierarchy: moisture content (most
relaxed density and impact resistance while minimizing influential) > forming pressure > heating temperature
relaxation ratio and specific energy consumption, > binder addition ratio (least influential). Process
allowing for low-pressure compaction of biomass optimization suggests that reduced moisture content
feedstock while maintaining high pellet quality. combined with elevated temperature effectively
minimizes temperature variation. Importantly, strong
4.2.3. The effect of temperature field uniformity on negative correlations exist between temperature
densified biofuel quality MSD and both relaxed density and impact resistance,
To investigate the relationship between temperature field confirming that precise temperature field control
uniformity and biomass densification quality, Spearman substantially improves densified biofuel quality.
correlation analysis was conducted using the Statistical
Package for the Social Sciences software (version 2022 Acknowledgments
to assess associations between temperature MSD
and both impact resistance and relaxed density. None.
This nonparametric method was selected due to the
nonnormal distribution of MSD data. Funding
The correlation analysis revealed a significant negative
correlation (ρ = −0.633, p<0.001) between temperature This study was funded by the Beijing Forestry University
MSD and relaxed density, indicating that increased (Award Number: 31500478, Grant Recipient: Zhongjia
temperature heterogeneity (higher MSD) corresponds Chen).

Volume 22 Issue 6 (2025) 69 doi: 10.36922/AJWEP025240195