Wood chips logistics to municipal heating plants — sawmill to silo

The chain in short

Chip delivery to a municipal heating plant is a sequence:

1. Loading at the sawmill (or forestry harvest site) — walking-floor trailer, net load 25–28 t, volume 90 m³
2. Road transport — typically 100–350 km for domestic, driver tachograph on work hours
3. Dispatch confirmation — 24 h before ETA (email or SMS), unloading window 2–3 h
4. Gravity unloading by walking floor into the customer zone — silo or pile

Not complicated but every step has traps. Practical below.

Walking floor — why this type

Chips are loose material at 250–320 kg/m³ density. Typical walking-floor trailer volume 90 m³ carries 22–29 t. Volume limits load, not mass.

Alternatives:

• Classic self-tipper — works, but pile discharge takes 5 minutes and needs space behind the truck. Awkward for closed silos.
• Open-top trailer — good for short runs but needs a tarp (rain = moisture).
• 20' / 40' container — used only for rail routes or plants without a siding running a container system.

Why walking floor is default:

• 90 m³ volume (largest available for road)
• Gravity discharge in 15–20 minutes
• Compatible with closed and open silos
• No loader needed at the customer

Weekly schedule — how to structure

A typical 5 MW municipal plant burns 40 t of chips/day at season peak (January–February), 25 t off-peak (October–December, March–April). Annual demand: ~10,000 t.

Recommended cadence:

• Jan–Feb (peak): 2 deliveries/day × 25 t = 50 t/day. Buffer shrinks fast; deliveries must be steady.
• Oct–Dec + Mar–Apr: 3 deliveries/week × 25 t = 75 t/week = ~10 t/day. Buffer builds.
• May–Sep (offseason): 1–2 deliveries/week or none (no burning, silo flushed monthly).

Requires a schedule agreed 8 weeks ahead. GFT sends annual schedules in April, refreshes quarterly.

Dispatch and unloading window

Dispatch = confirmation that a truck runs on a specific date/time. Standard:

• 72 h ahead — preliminary confirmation with date
• 24 h ahead — dispatch with ETA (±2 h)
• 2 h ahead — SMS with concrete time (±30 min)

Unloading window — time the customer has to receive the truck. Standard: 2 h from confirmed time. If the customer expects delays (earlier delivery, equipment issue), 6 h notice moves the window without surcharge.

Truck idle fee — if a truck waits > 2 h due to customer: 150 PLN/h. Above 4 h: 250 PLN/h. Polish market standard.

Gravity unloading — how it looks

The walking-floor trailer parks under the silo or in the unloading hall. Driver:

1. Positions the trailer to the receiver (silo, pile, conveyor)
2. Opens the rear doors
3. Activates walking floor (hydraulic pushers)
4. Chips discharge from the trailer's rear
5. Unloading takes 15–20 minutes with a healthy trailer

The customer does not need a loader for walking-floor discharge — the whole process runs on the truck's hydraulics. Many customers miss this and prep a loader "just in case" — unnecessary.

What the customer needs:

• Paved surface (asphalt, concrete) at the discharge point
• 20 m free space behind the trailer (for chips to fall freely)
• Receiver (silo with feeder, warehouse hall, or open pile up to 3 m)

Contract claim clauses

A typical GFT framework contract includes:

1. Weight clause

Settlement weight = certified scale (customer's or a bridge scale within 5 km). Truck weighed empty and full. Difference = batch net weight. Customer pays for scale-shown net weight — not for loading declaration.

2. Quality clause

Batch parameters (calorific value, moisture, ash) measured by the customer at an accredited lab (or lab of the customer's choice) at the supplier's expense for the first batch of every month. If parameters are out of range:

• Deviation up to 5 pp → within tolerance
• 5–10 pp → batch price cut 8–12%

• 10 pp → refuse option; replacement at supplier's cost

3. Availability clause

Supplier guarantees weekly schedule. If a delivery is > 24 h late due to supplier → contractual penalty 500 PLN/batch. > 72 h → replacement from alternative warehouse at supplier's cost (recommended for critical plants).

4. Price clause

Fixed seasonal price (October–April). No index clauses on standard Polish contracts (rarely used unless volume > 15,000 t/year).

Three typical operational issues

1. Higher moisture than declared

Walking-floor trailers often have no roof (some do, not all). Chips loaded after rain at the sawmill and transported 200 km → +2–4 pp moisture. For a tight-budget plant this is a real problem.

Fix: "tarp cover" clause on routes > 100 km in rainy periods (October–November, March–April). Surcharge 3 PLN/t.

2. Oversized fraction (sticks, fines)

Forestry chips carry non-uniform fraction. Pieces > 100 mm can jam a screw feeder in the customer's silo. Boiler off, manual stick removal.

Fix: "screening on 63 mm sieve" at the supplier. Fraction > 63 mm separated and sold elsewhere or delivered as a separate top-up batch. Surcharge 8 PLN/t.

3. Truck cannot reach the silo

Customer has a narrow entrance (bad geometry) or paving with limited weight capacity (truck mass > allowed). Driver refuses to approach the silo; pile discharge 50 m away → customer now needs a loader.

Fix: logistics audit of the discharge point before the first contract — entrance geometry, paving load capacity, clearance height (4.2 m minimum for a truck).

Summary

Chip logistics to a municipal plant is a simple operation — walking-floor trailer, dispatched schedule, 15-minute gravity discharge. But every detail (moisture, fraction, entrance geometry, weight clauses) matters for stable boiler operation and a predictable fuel budget.

Green Fuel Trading prepares a logistics protocol for every heating-plant customer — a document describing loading, transport, dispatch and unloading for that specific customer. It covers the annual schedule, claim clauses, dispatcher contact, and emergency procedures.

Contact the GFT team — logistics audit of your plant is free for prospects considering a seasonal contract from 5,000 t of chips.