Grain drying options: on-floor, batch and continuous

UK grain drying comes in three families: on-floor systems that dry grain slowly where it's stored, batch driers that do one load at a time, and continuous-flow driers that eat a steady stream of wet grain at high throughput. Which one suits a farm comes down to two questions — how many tonnes come off in a typical harvest, and how wet do they usually arrive? Get those honest and the choice mostly makes itself.

The wrong answer shows up the same way every time: a drier that can't keep pace with the combine, a wet pit that's full by 2pm, and a harvest that runs at the speed of the drying, not the cutting.

The three families

	On-floor (ambient/low-heat)	Batch	Continuous-flow
How it works	Fans blow air up through grain on a ducted floor	Fill, dry, cool, empty — one load at a time	Wet grain in one end, dry grain out the other, continuously
Speed	Slow — days to weeks	Moderate — hours per batch	Fast — steady tonnes per hour
Capital cost	Low to moderate (floor, ducts, fans)	Moderate	High, plus wet pit and handling
Running cost	Low (mostly fan electricity)	Higher per tonne	Fuel-hungry but efficient at scale
Best at	Trimming 2–4 points off near-dry grain	Mixed farms, varied crops, modest tonnage	Big tonnage, wet years, keeping combines moving
Weakness	Struggles with genuinely wet grain; weather-dependent	Throughput ceiling; someone has to manage batches	Capital tied up; wants steady feeding to earn its keep

On-floor: the store that dries

On-floor drying blows ambient or slightly warmed air up through grain sitting on a ducted or perforated floor — so the drier and the store are the same building, which is most of its appeal. Capital cost is the floor, the ducts and the fans; running cost is largely electricity. After harvest, the same fans do the cooling that keeps the heap below 15°C into autumn.

Its limits are physics. Air at ambient humidity can only remove so much water, so on-floor systems are at their best trimming grain that arrived at 16–18% down to a safe 14.5% — and at their worst in a wet harvest when everything comes in at 20% and the weather stays damp, because damp air dries nothing. Depth matters too: the deeper the heap, the harder the fans work and the slower the front moves. A catchy harvest can leave the top of a deep on-floor heap wet for weeks, which is exactly where heating starts.

As a rule of thumb, on-floor suits farms whose grain mostly arrives within 3–4 points of dry, with the store space to spread it at sensible depths.

Batch driers: flexible, and honest about their ceiling

A batch drier fills with wet grain, dries it, cools it, and empties — typically a few hours per cycle depending on size and how many points are coming off. Mobile and static versions exist from roughly 10-tonne batches upwards.

The strengths are flexibility and control. A batch drier doesn't care whether today's load is wheat, beans or oilseed rape; each batch gets its own settings, which suits mixed cropping and the fussier crops. Capital cost sits well below a continuous-flow installation, and there's no need for elaborate wet-side handling — though a wet holding bin saves a lot of 11pm trailer shuffling.

The weakness is arithmetic. A 12-tonne batch taking three hours is 4 t/h — say 90–100 tonnes in a long day. A modern combine can cut that before lunch. On modest tonnage that's fine; the drier runs on after the combine stops. But when the gap between cutting rate and drying rate is too wide, wet grain stacks up, and wet grain sitting in a trailer or heap for days is grain quietly deteriorating.

Continuous-flow: throughput, at a price

Continuous-flow driers move a constant stream of grain past heat and then cooling, at anywhere from 10 to 60+ tonnes per hour depending on the machine and the points removed. For big arable operations they're what keeps three combines cutting in a wet September.

They come with an ecosystem: a wet pit or wet bins to buffer incoming loads, conveyors and elevators to feed and clear the drier, and ideally someone keeping an eye on it. The capital bill for the full installation comfortably reaches six figures. Per tonne, though, a well-matched continuous drier is efficient — it runs at steady state instead of heating and cooling steel every batch, and its cost per tonne falls the more tonnes it sees.

That last point cuts both ways: a continuous-flow drier on a farm that only needs it one year in three is expensive insurance. Some of those farms are better served by a batch drier plus a merchant's drying charge in the bad years — commonly £15–£25/t commercially. The full cost comparison is its own subject.

Fuel, briefly

Most UK driers with heat burn kerosene, gas oil or LPG; some larger installations use gas or biomass, and on-floor systems are mostly electric fans with optional low-grade heat. Fuel choice moves the running cost meaningfully — drying typically costs £2–£3.50 per tonne per percentage point removed, and the fuel bill is most of that. What matters at the buying stage is less the fuel than the match: a drier sized to the farm's real wet-year tonnage, fed and cleared without hand work.

The bottleneck question

Before comparing brochures, do this sum: your realistic peak cutting rate in tonnes per day, the average points you'd need to remove in a wet year, and what the candidate drier removes per day at that spec. If the drier's daily throughput is well under the combine's, the drier sets the pace of harvest — combines wait, grain queues wet, and the capacity you paid for in the field idles behind the capacity you didn't pay for in the yard.

Run your own numbers through our grain drying calculator — weight loss and cost per load — before deciding how much drier the farm actually needs.

Frequently Asked Questions

What are the main types of grain drier?

Three families: on-floor systems that blow air through grain stored on a ducted floor; batch driers that fill, dry, cool and empty one load at a time; and continuous-flow driers that process a constant stream at high throughput. On-floor suits near-dry grain and doubles as storage, batch suits mixed farms with moderate tonnage, continuous-flow suits high tonnage and wet years.

Is on-floor grain drying any good?

Very good within its limits. It's cheap to run, the drier is the store, and the same fans cool the heap after harvest. But it's slow, weather-dependent, and struggles when grain arrives genuinely wet — it's at its best removing 2–4 percentage points, not rescuing 20% grain in a damp autumn.

How fast does a batch grain drier work?

Depending on size and moisture removed, a farm batch drier typically cycles in a few hours — a 12-tonne machine might manage 90–100 tonnes in a long day taking off 4–5 points. That's ample for modest tonnage, but well under what a modern combine cuts in a day, which is why bigger operations move to continuous-flow.

How do I know what size drier I need?

Match the drier's daily throughput at your typical wet-year moisture removal to your peak daily cutting rate. If the drier does markedly fewer tonnes per day than the combine, it becomes the pace-setter for the whole harvest. Be honest about wet years, not average ones — the drier earns its money in the seasons everything arrives at 18% plus.