A 30 m³ softwood kiln needs about 30,000–45,000 kWh of useful heat per charge.
Audience: sawmill owners, joinery owners, plant planners. Sawdust-fuel concept, Sawdust Fuel for a 30 m³ Wood Kiln.
Context and problem
Why look at sawdust
A kiln that dries timber uses a lot of heat over a long period. Most sawmills burn fuel to produce it. At the same time, sawdust and shavings are produced in large quantities during sawing and planing, and they often have to be stored, moved or disposed of.
The question this concept asks is simple: can the sawdust that is already produced replace part or all of the purchased fuel, and in which form?
Two routes are compared here. Option A converts sawdust into briquettes first. Option B burns loose sawdust directly in a dedicated furnace.
Process overview
From sawdust to kiln heat
The chain is the same for both options. Only the fuel form and the burning step differ.
Temperatures marked "? °C" have not been measured yet. The dryer inlet, 60–80 °C, is the only figure supplied so far.
Hot-water supply
Hot-water return
Kiln exhaust
Hot air in sawdust dryer
Flue gas
Sawdust and briquettes
Moisture of the sawdust is a key input. Wet sawdust burns poorly and lowers the heat that reaches the kiln. Drying time and method are not yet measured for this site.
Key numbers
The figures that drive the decision
Rough ranges for one 30 m³ softwood kiln charge and the sawmill feeding it.
8–12 t
Briquettes per charge
Estimate
14–22 t
Fresh sawdust per charge (42–63 m³)
Estimate
7,200–11,000 kWh
Drying heat per charge
Estimate
20–30 %
Kiln heat recoverable as waste heat
Estimate
8–11 m³/day
Sawdust per working day for four charges per month
Estimate
Rough estimates, to be confirmed with quotes and a plant planner.
Option A
Briquettes Pressed fuel
Sawdust is pressed into dense blocks. The briquettes are stored dry and fed to a burner or stove that is sized for them.
What it needs
A briquetting press and its power supply
Dry sawdust as input (press performance drops with wet material)
Covered storage for the finished briquettes
A burner that accepts briquettes
Trade-offs
Easier to store, handle and transport than loose sawdust
Extra processing step with its own energy and maintenance cost
Briquettes can be sold or used elsewhere if the kiln needs less fuel
Option B
Sawdust furnace Direct feed
Loose sawdust is conveyed by an automatic feeder into a furnace. Hot gases or hot water are passed to the kiln through a heat exchanger.
What it needs
Automatic feeder and furnace sized for sawdust
Heat exchanger and circulation to the kiln
Ash removal and a controlled air supply
Storage for sawdust close to the furnace
Trade-offs
No pressing step, so fewer processing costs
Fuel moisture must be controlled more tightly to keep the burn stable
Larger investment in the furnace and controls
Comparison
A, B1 and B2 side by side
Per charge of one 30 m³ kiln. Ranges are estimates until confirmed with quotes and a plant planner.
Criterion
A · Briquettes
B1 · Fresh sawdust
B2 · Dried sawdust
Fuel per charge
8–12 t
18–27 t
8.6–12.9 t
Storage volume
12–18 m³
52–78 m³
49–74 m³
Processing
Drying and pressing
None
Drying
Extra electricity
Press about 800–1,800 kWh
Low
Low
Sellable product
Yes
No
No
Main risk
Die wear and resin
Moisture and emissions
Boiler for fine sawdust
Ask a supplier
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Interactive tool
Fuel calculator
Enter your own values. The calculator uses one formula: fuel needed per load = heat needed ÷ (fuel calorific value × furnace efficiency). No values are pre-filled, so the result only means something once you enter measured figures.
Result
Enter values and press Calculate.
All results are estimates. Real fuel use depends on moisture, furnace losses, kiln schedule and control.
Risks and open questions
What is not yet known
Risks
Fire and dust risk in sawdust storage and feed lines
Unstable burning if moisture varies from batch to batch
Ash handling and emissions must meet local rules
Maintenance of feeders and presses under dusty conditions
Open questions
How much sawdust does the sawmill produce each week?
What moisture content does the sawdust have when collected?
How many kiln loads run per month, and what heat does each need?
Which option matches the existing kiln and its heat transfer?
What are the local prices and availability of purchased fuel?