What is wood pellet?
Wood pellet is a solid fuel that is produced by crushing and densifying waste timber like sawdust, forestry residues, industrial byproducts like old paper and forestry wastes. The length is 1-2 cm and the diameter is generally 6, 8, 10, or 12mm. It is possible to produce 25mm wood pellet at maximum. In Sweden, 6mm wood pellet is encouraged to use in house as it can realize the best condition of combustion. Wood pellet production doesn't need to add binder as lignin, an element of wood, plays a role of binder and helps to pelletize when it is melted by heat.
| Amount of heating generation (lower limit) | 4.7 kWh^kg about4,000 kcal^kg |
| Kerosene conversion value | pelletFkerosene about2.1tonsF1m3 |
| Volume weight | 650 kg/m3 |
| Hydrous rate | 8-13% |
| Ash | wood except bark: under 0.5%, bark: over 2.5% |
Characteristic of wood pellet is very easy to manage compared to other biomass fuel. As the shape and hydrous rate are stable, wood pellet is suitable to use in automatic combustion installation and it can remarkably save time and labor for both of electric power generation boiler and pellet stove for house. It is possible to transport long distance because wood pellet has high energy density and much energy can be transported at once. Also wood pellet which is heat-treated, can be stored in long term with less risk for molding.
| Advantages | High quality (shape and hydrous rate are stable) |
| dry, easy to store | |
| burning under environmental compliance is possible | |
| suitable for automatic combustion operation | |
| made of regional renewable resources | |
| energy density is higher than wood chips, suitable for transportation and storage | |
| transportable to areas with high energy demand density because of its high energy density | |
| ideal for closed renewable energy system | |
| possibility to be an alternative for energy system from smaller to larger scale | |
| create employment | |
| Disadvantages | labor-intensive more than heating with gas, oil and electric power in house |
| credibility in fuel supply, transportation and combustion is inferior to gas, oil and electric power | |
| need storage capacity three times as large as oil's | |
| weak to moisture |
Dried timber 1ton can generate energy equivalent to electric power 1,000 kWh or heat 4,500kWh. Energy ratio for pelletizing in comparison with wood pellet product's is as follows:
- To pelletize dried materials needs energy equivalent to 8-13% of energy contained in wood pellet product
- To pelletize materials (sawdust) after drying needs energy equivalent to 10-25% of energy contained in wood pellet product
- Whole process of pelletization of wood chip (including drying and crush) needs energy equivalent to 18-35% of energy contained in wood pellet product
