Based in the Scottish Borders, Mountfair Farming covers over 2000ha with a large proportion of the cereal drying being handled using heat from a 1MW biomass boiler. Íæż½ã½ã found out more.
Growing a significant area of combinable crops in the Scottish Borders will always involve some catchy weather and less than ideal cutting conditions. To address this, Mountfair farming uses a mixture of drying systems across multiple sites to achieve the 16,000 tonne capacity it needs.
Aidan and Jorin Grimsdale know the challenges only too well, but it has taken a while to get to the point where they are now comfortably able to handle all that the elements can throw at them.
Aidan says: For years we have focused on having enough drilling, spraying and combining capacity because without those vital tools you have got nothing ultimately.
Being a relatively young business we had to make do with what we had in other areas, particularly with our drying and storage facilities.
Solution
The solution to the storage and drying challenge was started in 2015 with the construction of a new 30 meters by 72 m building, which was extended further in 2021 to 102m.
Comprising of two 700 tonne drying floors there is also a 2019 48-tonne Opico 4810 Magna batch drier, which has recently been re-sited to its permanent position. The storage site is one of four grain stores with Opico driers operated by the business.
The site utilises a 1MW biomass boiler as its main heat source to dry a combination of feed-wheats and OSR, totalling 10,000 tonne annually.
The Opico 4810 unit is conventional diesel-fired model operated in combination with a heat exchanger fuelled with hot water from the main biomass plant.
Positioned about 60 metres from the main boiler, an additional insulated pipe circuit has been installed to bring the hot water to the dried mounted radiator.
The hot water is pumped through a large radiator mounted on the air intake for the drier, lifting the air up to 55degC from the ambient before being blown in. The diesel burner then lifts the air temp the remaining 45degC to the 100degC target operating temperature.
Reduction
The process of pre-heating the intake air has allowed for an over 50 per-cent reduction in the diesel requirement to run the unit.
Most of the time it runs on the low flame, accept on colder nights, the high flame is switched on too.
Initially we had some challenges in setting up the diesel burner, as the set up required some unusual nozzle jets. Originally even the low flame was burning far too hot, however once that was sorted and set up correctly it works well. said Aidan.
Included in the assembly is an automated valve which diverts the water flow once the drier burner cuts off during the cooling cycle.
The addition of the radiator has increased the cooling cycle by 25-30 minutes as this must be cooled down before cooler air can be pushed through the grain.
The cooling cycle is longer, but this is fairly consistent so we factor this in when running the plant and the time it takes to run a batch through the drier, said Aidan.
In terms of operating costs, using the biomass to pre-heat the air has made a significant difference to the cost per tonne to process the crop.
Fuel usage on the Opico in the first two years running on straight diesel was 4-5 per tonne and now it is running biomass we are around the 2-2.50/tonne mark - basically it has halved the drying costs. said Aidan
Alongside the biomass, other adjustments have been made to improve the economics of using the Opico drier.
We have also managed to reduce our electricity consumption. Because we do not currently have a meaty enough three-phase supply to run the drier we have been reliant on a generator.
It requires an inverter which has enabled us to tweak the drier fan. Rather than running at the standard 50Hertz, we have reduced it to 40Hertz.
The downside of that is that we have to run the drier slightly slower it is 10-15 per cent down but it means we have halved the generator fuel consumption.
That reduction in capacity is a penalty that is well worth paying the whole set-up is now so much more energy efficient, said Aidan
The biomass source is predominately windfall softwood which is purchased in round and chipped on site as required by a specialist contractor.
Moisture
We use roughly 300 tonnes of dry chip a year, but that does vary a bit depending on our intake source.
Usual moisture content for the chip is 20 per cent, we have had it as low as 18 and as high as 23 per cent. Obviously the wetter the chip, the more we use,saidAidan
The biomass plant supplied by Topling is automated and controlled through a central touchscreen. A hydraulic walking floor pushes the chips into the boiler intake auger, which regulates the fuel input based on the demand from the system.
The boiler is aligned to a Renewable heat incentive (RHI) scheme, so the capacity and its use to dry grain and a small amount of firewood on the drying floors are matched to optimise this system.
The drier, elevators and store handling are all automated through a central control, linking the demands of the drier and the output of the dried crop.
A recent installation of a large wet pit has allowed more utilisation of this system, reducing the labour requirement to operate the plant.
Aidan says For the first two seasons we had the 48-tonner set-up up outside with a 25-tonne bin feeding it but it meant having someone on hand all the time to keep it running at full capacity.
Last winter the store was completed, the dryer fully integrated, conveyors installed and a 300-tonne wet grain bunker installed with a proper trench intake conveyor to keep it constantly fed.
With it wired into the driers touchscreen computer, it now loads and unloads itself under its own steam.
It has totally revolutionised the job so that it will process 150-tonnes without anyone going near it. I can now load up the bunker at 11pm and leave it running all night.
Dropping 17 per cent moisture grain down to 14.5 per cent. It will take about three hours per batch, doing three batches before it needs any attention. said Mr Grimsdale.
In the two seasons that the Grimsdales ran the 48-tonne drier in its temporary position with 25-tonne intake bin it required someone to be on site all the time it was running, loading the hopper and managing the driers discharge.
That often meant it might sit idle through the early hours of the morning until someone arrived to start loading it
With addition of the 300-tonne intake bunker and some changes to the store discharge system, Aidan estimates that the requirement for human input has been reduced by an average of six hours every day.
