How biomass can help farmers slash grain drying costs

Grain drying can be a costly exercise for arable farmers and one way to cut fuel costs is by opting for renewable heat with biomass boilers, but what are the potential savings for commercial grain stores?

John Seed, director of Topling Biomass Energy Systems, says biomass boilers are cheaper than traditional fossil-fuelled boilers, with the added attraction that farmers are in control of their own fuel supply.

“There is not the worry about future cost spikes and they also help to reduce carbon emissions.”

Fuel saving is the real key, says John Farquhar, senior biomass consultant at SAC Consulting.

“If kerosene is priced at about 40p/litre and straw at £50/t, you could save about £1.50 for every tonne of grain dried.”

When compared against diesel at 55p/litre, the saving would be £2.50/t dried.

See also: How one grower went about upgrading his grain store

Woodchip v straw

Woodchip offers smaller savings than straw, but at a cost of £100/t, it could save between 50p and £1.50/t dried.

“These figures are based on a relatively low fossil-fuel price but if this were to go up, you could be looking at much bigger savings,” says Mr Farquhar.

The savings also depend on the efficiency of the biomass boiler system, so that is something to consider when looking at the available options.

The main question is whether it is economically viable to install a biomass boiler if it is only being used for a few months of the year to dry grain.

“It really needs to be put to multipurpose usage if it is going to be worthwhile,” says Phil Metcalfe, agricultural engineer and consultants for Adas.

“There is potential to look into drying green crops with a high temperature airflow system – although that is very much a niche market.”

Other options

Drying woodchip and firewood are other possible options.

Mr Farquhar believes that drying woodchip is a good alternative to fit alongside grain drying, but recommends securing an end market before committing to it.

“It is also good to consider the drying system as an on-floor system is capable of drying more products than a continuous-flow drier.”

Biomass boilers can also be used for supplying hot water and heating houses or other buildings, but that depends on boiler size, he adds.

“There are opportunities to incorporate the boiler into district heating schemes or for heating a large house but often the boilers are bigger than is necessary for house heating.”

Renewable Heat Incentive

Ofgem is pushing renewable energy through the Renewable Heat Incentive (RHI), which has been fundamental in kick-starting the industry, says Mr Seed.

The payments are based upon boiler size and kW hours of energy or heat produced, payable for 20 years from installation.

“It is only because of the subsidy that many people have been able to get set up.”

However, it may be worth applying sooner rather than later as the medium tariff RHI is likely to be cut in the next five months or so, with further cuts likely in the longer term.

Other grants or funding are not permitted alongside the RHI and boilers need to meet an emissions standard to be eligible.

From October 2015 the rules will change for existing and new participants so that the fuel must also meet sustainability criteria.

When drying grain, a wet harvest could cause a bottleneck so keeping a kerosene boiler for back up is a sensible idea, says Mr Farqhuar.

“Under the RHI every 100kW of installed capacity will give you about 1.3t of dried product an hour (assuming the dryer is about 50% efficient).

“If you want to stay below the 1MW threshold for the higher RHI tariff you can only achieve about 12-13t an hour on biomass alone.

“Therefore if you need a faster rate you will require additional heat sources such as a kerosene burner,” he says.

Another limitation to the RHI is that it requires an indirect heat system via water or steam, which complicates the boiler system and cannot supply the same temperatures as direct heat transfer.

Biomass boilers are not a self-sufficient option either, as they require electricity to power the fan.

Solar photovoltaics

Richard Sowden, a renewable energy consultant for Adas, therefore, suggests running it alongside solar photovoltaics to produce electricity for the fans.

Deciding which type of boiler to buy depends on the size and type of fuel it is able to burn.

For the purposes of grain drying and keeping RHI in mind, Mr Farquhar recommends a boiler between 200kW and 1MW.

Anything above 1MW suffers a large reduction in RHI and is for very large-scale grain drying.

Different boilers can burn straw, wood, woodchip or pellets, and some can burn grain, says Mr Seed.

“Choosing the right boiler is based on size, fuel, temperature output, ease of maintenance and finance.”

It is also good to be aware of labour requirements as the boiler could require considerable man hours during a busy harvest to reload with fuel.

John Seed

John Seed, Woodend Farm, Berwickshire: Self-sufficiency and reduced costs

John Seed, director of Topling biomass energy systems and a member of the Woodend Farming Partnership, installed a 950kW biomass boiler at Woodend Farm, Berwickshire, in 2012 to dry grain.

He now dries logs and firewood as well as running a district heating system and hot water from it.

“We were looking to reduce energy costs and become as self sufficient as possible,” he says.

The 205ha farm grows winter wheat, winter oats, spring barley and spring beans alongside woodland and conservation crops.

“We have borrowed about £1m from the bank to set the entire system up and hope to pay this back over 10 years.”

Mr Seed initially installed a 450kW boiler but was unable to heat the drying floor to the required temperature, so in 2012 he swapped to a 950kW boiler which can burn different types of straw as well as woodchip and logs.

“We have borrowed about £1m from the bank to set the entire system up and hope to pay this back over 10 years.”
John Seed, Woodend Farm

It heats the drying floor to 40C via a 100,000-litre accumulator tank which is useful as a batch boiler, working to the highest capacity and storing heat not needed immediately.

“The water temperature never falls below 50C and will build up to 85C which then heats the two 600t drying floors via a 900kW water-to-air heat exchanger.”

In 2013, Woodland Farming Partnership dried over 3,000t of cereals, oilseed rape and beans, which, without the biomass boiler, would have required 60,000 litres of oil,” says Mr Seed.

“While drying grain we have to clean, refill and light the boiler twice a day, but throughout the winter it only gets lit once every three days because of the accumulator tank.

“It takes about 250kg of straw each time so we get through about 180t of straw a year,” he adds.

Aberdeen grain, Newmachar, Aberdeenshire: Biomass helps to tackle fuel price volatility

Aberdeen Grain is about to enter its second harvest with a new biomass boiler.

The £1.25m investment was entirely funded by the co-op’s 185 members, and is expected to pay back in just six years.

Managing director Bruce Ferguson says the biggest cost to the co-op was fuel, at about £700,000/year.

“The idea behind installing a biomass system was to take the risk and volatility of fuel prices out of the business.”

Drying about 75,000t/year of grain, Mr Ferguson wanted a semi-automatic system to minimise labour requirements.

“We were looking for a robust and simple system that would have the capacity to make sure we were not relying on fossil fuels,” he says.

“We were looking for a robust and simple system that would have the capacity to make sure we were not relying on fossil fuels.”
Bruce Ferguson, Aberdeen Grain

An LPG boiler is kept as a backup but has hardly been used.

The plant is now the largest in the country with a 6MW boiler that heats a 160,000-litre water tank to 100C.

This is then stored in an accumulator tank which feeds into radiators that heat the air going into three continuous-flow dryers, drying 80-100t/hour of malting barley.

“It is a multifuel boiler, but we believe it’s best to remain consistent with the fuel,” says Mr Ferguson.

“We experimented with wet woodchip, but found dry woodchip, below 25% moisture, helps to maximise output.”

The plant gets through about 1,200t of woodchip over the 12-15 week operational period.

The boiler should last 25 years or more, and Aberdeen grain is considering different projects to use the system year-round.

“We are learning all the time but so far it has worked very well.”


Tariff name

Eligible technology

Eligible sizes

Tariffs (p/kw hour)

Small commercial biomass

Solid biomass including solid biomass contained in waste

Less than 200kw Tier 1 (up to 1,314kwh)


Medium commercial biomass

Less than 200kw Tier 2 (over 1,314kwh)


200kw and above and less than 1mw Tier 1  (up to 1,314kwh)


Large commercial biomass

200kw and above and less than 1mw Tier 2  (over 1,314kwh)


1 MWh and above


Source: Ofgem