Whole-tree chippers
Whole-tree chippers convert stems, tops and slash into chips. They sit between harvesting machinery and biomass processing.
Potential commercial outputs include pulp chip, biomass fuel, landscape chip and simple residue reduction.
Vermeer WC2300XL
Australian published specifications include:
- approximately 440 hp / 328 kW
- approximately 14.8 tonnes
- roughly 584 mm material capacity
- 864 mm infeed roller width
- dual-chain infeed
- remote control
- replaceable high-wear components
Commercial consideration
The machine requires a consistent feed system.
A 440 hp chipper waiting for an excavator to bring one tree at a time is expensive idle capital.
A high-production chipper should be analysed together with:
- loader
- grapple
- skidder
- truck availability
- chip trailer capacity
- destination
The chipper is rarely the bottleneck by itself. The feed and the haulage usually are.
Large brush chippers
The line between arborist chipper and industrial forestry chipper becomes blurred at the top end.
The Vermeer BC2100XL, for example, has:
- 275 hp / 205 kW
- 40 × 24 inch infeed opening
- approximately 533 mm rated material capacity
- approximately 4,536 kg theoretical feed pulling force
- around 8 tonnes aggregate trailer mass
This type of machine can suit large arboriculture, council vegetation, clearing contractors, storm cleanup and waste timber — but it is not the same production class as a large whole-tree chipper, and it should not be quoted as though it were.
Horizontal grinders
A horizontal grinder is generally preferable when the material is:
- dirty
- mixed
- contaminated
- irregular
- stump-heavy
- demolition-derived
Products can include biomass, mulch, boiler fuel and compost feedstock.
The commercial trade-off
| Chipper | Grinder |
|---|---|
| Cleaner product | More tolerant feed |
| Sharp knives | Hammers / grinding system |
| Better uniform chip | Broader waste handling |
| Sensitive to contamination | More tolerant |
| Forestry fibre | Waste/recycling |
The choice is determined by feedstock and by the product specification the buyer of the output will accept. It is not a productivity comparison, and a machine chosen on throughput alone will be the wrong one roughly half the time.
The rule that governs this sector
The machine choice should follow the biomass offtake agreement. Do not build the fleet before knowing:
- chip specification
- moisture
- contamination limits
- tonnes required
- delivery point
- transport requirement
An out-of-specification load is rejected, not discounted. That asymmetry is why the offtake agreement has to come first.
The offtake agreement comes first
Biomass is the one application in this guide where the fleet decision has a strict prerequisite. Chip specification, moisture limit, contamination tolerance, annual tonnage, delivery point and transport responsibility together determine whether the correct processor is a chipper or a grinder, what feed capacity is needed, and whether the haulage distance is viable at all.
The reason the ordering is strict rather than advisable is the failure mode: an out-of-specification load is rejected rather than discounted. A fleet producing the wrong product produces nothing saleable, and the capital is committed to a specification it cannot meet. Buying the processor and then looking for the market is a bet that the market happens to want what the machine makes.
Feed rate is the real constraint
A processor's rated throughput assumes continuous feed. Real production is set by how fast material reaches the infeed and how quickly full trucks are replaced — neither of which sits inside the processor.
This is the most common capital mistake in biomass work, and it is invisible in a specification comparison. A high-horsepower chipper fed by a single excavator bringing one stem at a time produces a fraction of its rating while consuming most of its cost, and the shortfall is attributed to the machine rather than to the feed.
Sizing the feed means a dedicated loader with a grapple, material staged ahead of the machine rather than fed from the stump, and truck cycle capacity confirmed before processing capacity is bought. The test is simple: if the processor is waiting, the feed is undersized, however impressive the rating.
Haulage frequently decides viability
Biomass is bulky and low in value per tonne, which makes delivered cost — processing plus haulage — the only figure that matters commercially. A contract that works at 40 kilometres may not work at 120, and no amount of processing efficiency compensates for a delivered cost above the offtake price.
Model it at the actual distance and payload rather than from a rule of thumb, and do it before the equipment decision rather than after. Where the haul is marginal, the useful questions are whether a closer buyer exists and whether the material can be densified — not whether a faster processor would help.
Wear cost per tonne
Knives, hammers, screens and tips are consumed in proportion to throughput, and contamination accelerates all of them sharply. Soil is the dominant variable: material that has been dragged across the ground costs substantially more to process than material handled clear of it, and the effect shows up in wear parts, in fuel and, on a chipper, in specification compliance.
Track wear cost per tonne from the first load rather than budgeting an allowance. It is the input most likely to differ from the original model, and it is also a diagnostic — a step change means something has altered in the material, the handling or the machine.
Two operating disciplines control most of it: keep material off the ground wherever the operation allows, and change knives or tips on condition rather than deferring.
Moisture and contamination management
Where the offtake specifies a moisture range, moisture is a scheduling problem rather than a machine problem. Drying and stockpile time have to be planned into the operation, and material should be measured before dispatch rather than discovered at the weighbridge.
Contamination is a cost and a rejection risk simultaneously, which is why it is worth treating as an operating discipline rather than a presentation issue. Soil affects wear rates, moisture content and specification compliance at the same time, and on a chipper it can put a load outside the buyer's tolerance entirely.
Stump biomass
Stumps carry soil, which makes them the hardest material in this category. Recovery generally makes commercial sense only where three things are true at once: a grinder is already in the fleet, the buyer tolerates the contamination, and the stumps had to be removed anyway for site preparation. Where stumps would otherwise be left in place, the recovery cost rarely justifies itself on the biomass value alone.
See chipper versus grinder for the detailed trade-off, the biomass contractor package for how the fleet is configured around an offtake, and the bottleneck principle for why feed rate rather than processor rating sets production.
Product size is a screen and a setting, not a machine
Buyers frequently ask which machine produces the right product. The more accurate answer is that the machine determines the kind of product and the configuration determines its size and consistency.
On a grinder, screen selection is the primary control over output size: a smaller screen produces finer, more uniform material and costs throughput and fuel, because material is retained and re-processed until it passes. On a chipper, knife condition, anvil clearance and feed speed govern chip size and consistency, and all three drift with wear.
Two practical consequences:
Ask what configuration produced a sample. A demonstration sample tells you what the machine can produce, not what it produces all day at the throughput you need. Screen size, knife condition and feed rate should all be recorded alongside it.
Specification compliance has a throughput cost. A tighter product specification means a smaller screen or slower feed, which means fewer tonnes per hour at the same cost per hour. Where a buyer's specification is tight, model the throughput you will actually achieve under it rather than the machine's headline rating.
Moisture changes what you are paid
Where material is sold by weight, moisture is part of the transaction, and it moves in both directions.
High moisture adds weight — which sounds favourable until the contract specifies a moisture range, at which point an out-of-range load is a compliance problem rather than a heavier one. It also affects energy content for fuel applications, which is why energy buyers specify it.
Drying is a scheduling problem rather than a machine problem: stockpile time, stockpile geometry and season all affect it, and none of them are addressed by buying a different processor. Two disciplines follow:
- Measure before dispatch, not at the weighbridge. Discovering a moisture problem after transport has already been paid for is the expensive version.
- Build stockpile time into the operation. Where the specification requires it, material cannot go straight from stump to truck, and a schedule that assumes otherwise will fail on the first load.
Designing the infeed
A processor's rated throughput assumes continuous feed, and the feed is where most biomass operations actually lose production. Designing it deliberately is worth more than any specification difference between comparable machines.
| Feed arrangement | Typical result |
|---|---|
| Excavator feeding directly from the stump | Processor waits between stems; a fraction of rated throughput |
| Dedicated loader, material staged ahead | Near-continuous feed; close to achievable rating |
| Loader plus staged material plus trailer swap plan | Continuous through truck changes; the practical maximum |
The third row is the one that separates operations that hit their model from those that do not, and the thing it adds is not a machine — it is a plan for what happens when a trailer fills. A full trailer stops the processor as effectively as a breakdown, and on a high-throughput machine it happens often.
Chipper and grinder wear behave differently
Both are wear-intensive and the wear has a different character, which matters for how you budget and how you operate.
Chipper knives are precision components. They cut cleanly while sharp and degrade product consistency as they dull, and they are intolerant of soil and foreign material — a single piece of metal or a stone can damage knives and anvil together. Running dull knives to defer a change raises fuel per tonne, degrades the product and loads the machine harder, so the deferred cost arrives as fuel and rejected loads rather than as a parts invoice.
Grinder hammers and tips are impact components. They tolerate contamination that would damage a chipper and wear steadily rather than sharply, which makes their cost more predictable and generally higher per tonne. Screens wear too, and a worn screen passes oversize material.
In both cases the dominant driver is the same, and it is the one covered under wear cost above: soil. Keeping material clear of it is a direct cost control, not tidiness.
Contamination is three problems at once
It is worth being explicit about why contamination gets so much attention in this sector. Soil and foreign material affect:
- Wear rates — accelerating knife, hammer, tip and screen consumption.
- Specification compliance — ash and contamination limits are common in offtake agreements, and an out-of-specification load is rejected rather than discounted.
- Moisture measurement — soil carries its own moisture and distorts what you are being paid for.
Three costs from one cause is why experienced operators treat material handling as the discipline that decides biomass profitability, ahead of processor selection.