What a biomass drying plant costs to run
The method, on your own numbers.
Five lines make up the running cost of a biomass drying plant: fuel, electricity, labour, consumables and maintenance. Fuel is calculated from evaporative load divided through an overall efficiency near 0.40. The other four are site-specific, and none of them can honestly be quoted from a catalogue.
Why this article has no numbers in it
Every figure that would make an operating cost real is yours rather than ours: the delivered price of your residue, your electricity tariff, your labour rates, your ambient conditions and your product. A supplier who publishes a running cost has invented four of those five, and the resulting number tells you about the supplier rather than about the plant.
What can honestly be published is the method — which lines exist, how each is calculated, and which one dominates. That is set out below, and it is enough to fill in with your own figures in an afternoon.
The five lines
Fuel almost always dominates, and it is the only line that follows from the engineering rather than from the site. The other four are smaller individually and together are not negligible.
| Line | How it is calculated |
|---|---|
| Fuel | Water removed per hour → evaporation load in kW → ÷ overall efficiency ≈ 0.40 → fuel input → ÷ calorific value → kg/h → × your delivered price |
| Electricity | Connected load × running hours × your tariff. Fans and the feed system, not heat |
| Labour | Operators per shift, plus a daily de-ashing and cleaning routine set by ash content |
| Consumables | Grates, filters and seals. Grates are wear items and their life follows the fuel |
| Maintenance | Scheduled exchanger cleaning and bearing service; unscheduled work if the schedule slips |
Note what is absent: no capital charge, no depreciation and no financing. Those belong in your own appraisal, not in a supplier’s article about running a machine.
Working the fuel line
Start with water. Fresh intake minus dried output is the water to remove; divide by cycle hours for the rate in kg/h. Convert to an evaporation load in kilowatts, add envelope loss, and divide by overall fuel-to-evaporation efficiency — around 0.40 once combustion, the generator, the ducting, the envelope and the exhaust are all counted.
That gives fuel input in kilowatts. Divide by your fuel’s calorific value in the units you buy it in, and you have kilos an hour. Multiply by the delivered price and by running hours. The arithmetic is short; the honesty is in using 0.40 rather than the 85 % combustion figure suppliers tend to quote.
The comparisons worth making, and the one to avoid
Compare fuels on delivered cost per unit of usable heat, not on price per tonne — a cheap wet residue with high ash frequently loses to an expensive dry one once cleaning time is counted. Compare configurations on cost per kilo of water removed, which is the only figure that is fair across chamber formats.
The comparison to avoid is a single headline saving. It depends on the fuel you are leaving, the fuel you are arriving at, the utilisation you achieve and the tariff you pay, and a number that depends on four unknowns is not information. We publish the method and let you produce the number.
Frequently asked questions
Why will you not publish a running cost?
Because four of the five inputs are yours: your delivered fuel price, your tariff, your labour rates and your utilisation. Only the engineering half — evaporative load through an efficiency near 0.40 — is ours to state. A published total would be a guess about your site dressed up as a specification.
Which running-cost line is the largest?
Fuel, in almost every case, and it is also the one that follows from the engineering rather than from the site. That is why the efficiency chain matters: at 0.40 overall, every point of efficiency is a direct percentage off the largest line on the list, every hour the plant runs.
How do I compare two fuel offers properly?
Divide delivered price per tonne by calorific value, correct for the moisture it actually arrives at, then add the operator time its ash content costs you. A residue at 3,800 kcal/kg and 10 % ash can easily lose to one at 4,800 kcal/kg and 3 % ash even at a higher price per tonne.
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