Page 67 - AJWEP-22-6

Pine sawdust biofuel: Quality and temperature optimization

equivalent to 0.68–1.4 billion tons of standard coal, durability, making it the preferred choice for cost-
representing substantial untapped resources. Pine sensitive projects. Under high-pressure forming,
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sawdust, a major forestry waste stream, currently adding 1–3% sweet potato starch can meet industrial
poses significant environmental burdens through requirements, with 2% achieving a pellet durability of
conventional disposal methods (e.g., open burning, 95.6%. 14
landfilling), including land occupation and emissions of Heating temperature critically influences pellet
toxic compounds and greenhouse gases. Densification quality through lignin softening, which promotes
into densified biofuel offers a viable waste valorization particle bonding and densification. While elevated
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strategy to advance the circular bioeconomy in the forming temperatures enhance pellet density and
forestry sector. 2 strength, excessively high temperatures may cause
The primary factors influencing biomass densification surface charring, ultimately compromising durability.
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include forming pressure, moisture content, binder Within the 30–110°C range, densified biofuel density
addition ratio, and heating temperature. Among these, and hardness exhibit a parabolic relationship with
forming pressure plays a particularly critical role in temperature, peaking at approximately 70°C.
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determining pellet quality: optimal forming pressure Preheating treatment can improve the durability of
ensures high-quality pellets with minimal energy input, high-moisture-content particles. Short-term treatment
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whereas excessive pressure may cause blockages, and at 200°C can achieve the impact resistance of 99.5%,
insufficient pressure can lead to substandard pellets. but it requires a moisture content of ≤12%. 19
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Under pressure, sludge particles are extruded into the Current research predominantly examines the direct
voids of biomass pellets, where protein denaturation thermal effects, with limited investigations addressing
and lignin softening occur, acting as natural binders that temperature field distribution and its influencing factors.
facilitate biomass densification. 4 To address this gap, the present study concentrates on
Moisture content plays an equally critical role; pine sawdust densification technology for high-value
excessive moisture reduces pellet strength, while waste valorization. By systematically evaluating key
insufficient moisture increases energy consumption parameters (forming pressure, heating temperature,
during molding. Although increased moisture content binder addition ratio, and moisture content) and
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reduces molding energy consumption, the pellet’s their interactive effects on biomass pellet quality, we
relaxation coefficient initially decreases before introduce temperature mean square deviation (MSD)
increasing, potentially due to water acting as a lubricant as a novel metric for characterizing temperature field
that reduces interparticle friction. The density and uniformity. This approach elucidates its functional
durability of municipal solid waste-derived briquettes mechanisms in densification processes and regulatory
are significantly affected by both moisture content effects on fuel performance. The optimization of process
and particle size distribution. The moisture content parameters and temperature field distribution aims to
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significantly affects pellet bonding quality. If it is too improve pine sawdust pellet quality, thereby providing
low, insufficient lignin plasticization leads to weak both theoretical foundations and technical solutions for
bonding; if it is too high, it triggers a steam explosion industrial-scale applications (e.g., industrial boilers,
effect, reducing densified biofuel durability. 7 residential heating systems). This research contributes
Binders, including glycerol or lignin-rich additives, to enhanced forestry waste utilization and promotes the
significantly enhance densification performance and development of low-carbon circular economies.
pellet durability. The incorporation of 5–20% coal into
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biomass improves pellet durability while maintaining 2. Determination of factors influencing densified
thermal properties. When sawdust and asphalt are biofuel and quality evaluation indicators
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added as binders to sludge, the resulting densified
biofuel exhibits increased calorific value, demonstrating 2.1. Determination of experimental factors and
potential for coal replacement. Similarly, the levels
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NovoGro binder application in densified biofuel Building upon previous research findings 20-23 while
production enhances both durability and mechanical maintaining pine sawdust formability, this study adopted
strength. These binder applications collectively the following experimental parameter ranges: forming
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improve densification efficiency while reducing energy pressure (A) within 10–50 MPa, moisture content, (B)
consumption. Adding a binder increases the cost within 10–16%, binder addition ratio, (C) within 1–5%,
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by $0.15 USD per ton for every 1% improvement in and heating temperature, (D) within 150–190°C. An

Volume 22 Issue 6 (2025) 61 doi: 10.36922/AJWEP025240195