The harvest of 2014 will be remembered for different things by different people. For many, it was good yields, low moistures and relatively easy cutting. Indeed, were it not for the bad price, we might remember it as an excellent year.

The same things apply for the Whyte brothers in the Naul, Co Dublin, but for them 2014 will be remembered as the year when they broke the link with oil for grain drying.

A significant decision was made to purchase a straw-burning unit to heat the air to dry their grain. This effectively enabled the removal of an oil bill of up to €60,000 from the list of farm costs for grain drying.

The decision to do this was not taken lightly. Many different types of burner were considered, but the decision was ultimately made to purchase a 2.4-megawatt Graso burner from Poland. This burner is bigger than necessary, but it was purchased to cope with higher drying capacity in the future. Local man Conor Bruton is agent for the burners.

Hot air

The objective was to use this burner to heat air that would then be blown through an insulated air duct to heat the dryer. This was to replace the oil-fired heat source in the Tallaght-manufactured mixed-flo dryer that had already given many years of good service.

There were concerns initially as to whether this burner could be made to work at all. Could it deliver a sufficient temperature in the air going into the dryer to enable it to work efficiently? Would the heat supply be stable? They had visited a Scottish grower who was using this burner to provide heat for his dryer, but this was fuelled by a continuous feed of woodchip rather than batch-fed straw.

The bales

The Graso burner was designed with a round chamber and a round front door to take big round bales. But this would not work for Whytes because it could mean a bale every 15 minutes. This level of inconvenience would outweigh the cost benefit.

A system was needed to feed the burner with 8x4x4 big square bales, or else it would not be feasible. They already had these balers. The burner manufacturer had never seen big bales used in the burner, and was aware of the difficulty in doing this.

The challenge was easy to understand. Within seconds of putting a big bale into the burner chamber, the twines would burn off and the bale could scatter anywhere. And if you stuck a spike into the bale, it would not come out easily and one could end up pulling fire out around the yard. When the twines burn off a round bale, it largely stays together.

Another problem is the intense heat coming from the chamber when the door is opened. This would be a big challenge for hydraulic hoses and rams. The solution to the handling problem was the manufacture of a simple mechanical bale-handling device.

The solution was designed and manufactured on the farm and involved mounting a mechanical grab system on two big extension arms that went all the way into the burner chamber. This meant that all hydraulic hoses and rams on the loader were kept away from the intense heat.

Pioneers

Once a mechanism for handling square bales was available, the burner option was back on the cards again. And despite the remaining questions, the decision was made to purchase the burner knowing that there was still a lot of pioneering work left to be done by the Whytes themselves.

Solving problems would never daunt the multi-skilled brothers, who have developed the range of specialisations needed to run a big farming business. Peter Whyte looks after the yard and he spoke to me about the dryer.

A significant amount of site work had to be done in advance of the 30t unit arriving by road from Poland. It arrived earlier this year and has since been installed and is now working, with some tweaks and modifications.

The different plumbing and connections were done in advance of harvest, but one never knows for sure how something will work until it is put to work. Three hundred bales later, Peter Whyte is very happy with the new burner. He is using both rape straw and oaten straw in the new burner, alternating one with the other.

Straw quality

The best straw for burning is not nice golden straw, but bleached straw that has got a bit of weather. Fresh golden straw is more likely to give problems in the burner as it is much more prone to forming clinkers. Rainfall prior to baling helps to wash out an amount of the chlorine and other substances which cause problems in the burner.

Peter told me that the rape straw has performed very well in the burner, but they are adding a bit of lime with the oaten straw bales to help prevent clinker formation.

Bales must be dry and uniform, so headlands are now being chopped. When the straw is dry enough at baling, the bales can be made tighter and heavier. This means more fuel per fill.

Different figures exist for heat value of straw compared to diesel. Moisture content will obviously impact here, as will the type of straw. It is generally suggested that a big bale (480kg) of wheat straw is broadly equivalent to 150-160 litres of diesel in heat value. Expressed another way, roughly 3.0 to 3.2kg of straw is equivalent to one litre of diesel.

Peter estimates that the rape straw is giving roughly the equivalent of 160 litres of diesel per bale. The daily straw requirement is roughly 15 to 17 rape and oat bales.

The burner is not currently being run 24 hours a day, as there is adequate capacity in the dryer, so it has to be restarted each morning. But while it takes a little time to get the heat up in the morning, this is more than offset by the residual heat in the burner as it shuts down each evening.

Working the burner

Fuelling the burner involves the opening of the main front door and the insertion of a big bale each time. Once a new bale goes into the burner, combustion is controlled by computer to generate the target heat output on a continuous basis. Combustion is largely controlled by blowing air into specific parts of the combustion chamber.

The transfer of hot air from the burner to the dryer is via indirect heat transfer. This means that no direct flame or sooty material can transfer from the burner to the dryer or the grain.

There is a series of pipes inside the burner which are used to transfer the heat from the fire on one side to the air on the other. Air from the outside is pumped through the heat exchanger using two high-capacity centrifugal fans.

These are also bigger than necessary to cope with a higher air requirement in the future.

The air is heated to the desired temperature as it passes through to the burner. This is then moved through a heavily insulated pipe to minimise any heat loss between the burner and the dryer, which is about eight metres away.

The air temperature going to the dryer was a steady 105-110 degrees centigrade. The temperature in the brick-lined furnace was much higher at around 600°C. In the initial days of use, Peter told me that he attempted to control the whole process manually, but he was disappointed with the output and efficiency.

However, when he allowed the burner to control its own affairs, the general output increased in both the burner and the dryer. Indeed, he said that the system of heat transfer is actually helping the performance of the mixed-flow dryer as the forced air is driving more heat uniformly through the drying chambers.

Ash is always a concern when solid fuel sources are used. Peter estimated that it will take just over 400 bales to dry the 10,000t of wheat in store, averaging about 25t of dry wheat per bale. This is helped by the fact that much of the grain was below 20% moisture this year.

Most of this has already been dried using about 300 odd bales, and the total ash from this would be about the full of a big grain bucket.

The burner came with a manual ash removal system using a type of hoe that was used in a channel at the base of the burner. Since then, an automated auger system was installed which pushes the ash out through the chamber at regular intervals into an ash bin outside.

However, this modification was not without its challenges. Some of the straw had been raked prior to baling and this resulted in small stones in some bales. Some of these stones subsequently blocked the auger and the combination of the heat and the power of the motor rung off the auger shaft. Even the very heat-resistant materials broke.

The plan now is to use very heat-resistant material in the auger shaft and also to fit a pressure sensor on the motor. So if a blockage occurs the motor will immediately reverse to release the blockage and then turn again to continue its job.

Maintenance

The requirement for ongoing maintenance remains uncertain. Inevitably there will be items that will need replacing, such as door seals and motors. Regular cleaning of the pipes in the heat exchange mechanism is required.

This was to be a physical job with a wire brush, but that was slow and awkward. A vacuum tanker is now used to either blow out the fine ash from these pipes or to suck it up. A steel pipe is fitted to the end of a flexible hose and this is pushed into the pipe in the heat exchanger. When the ash is being sucked up, the vacuum tanker is half filled with water to capture the dust and protect the pump.

There has been a bit of tweaking involved in getting the burner set up. But the main issues are now ironed out and most concerns are either fixed or being fixed.

One unexpected challenge arose during refuelling. When a new bale is put into the burner, the charge of air and the readily combustible exterior of the bale result in a short gush of dark smoke from the burner. This was not foreseen as other users were not opening the main door for fuelling.

However, the problem has already been minimised and a number of solutions are being planned for next year.

Economics

“Based on the experience to date, it looks like we will have the investment paid back in three years,” Peter commented.

The burner and its complete installation cost in the order of €120,000 ex VAT. It would have been necessary to invest in some repairs for the existing oil-fired burner either way, so the effective cost is lower. But the oil burner is still in place if needed.

The amount of oil saved by replacing it with straw will vary from year to year and the moisture levels in the delivered grain. But with recent annual bills of around €60,000 for grain drying, this is a good base figure to begin with.

Peter values the rape and oat straw at around €30 per 8x4x4 bale. This puts the 400 bales at a cost of €12,000 for the straw versus the €60,000 for the oil – a potential €48,000 savings per year. And the more oil that might be needed, the bigger the saving and the quicker the payback.

The straw comes from their own crops from adjacent fields to minimise handling and transport costs. It will be supplied from around 100 acres of a combination of rape and oats. And straw from both of these crops was difficult to move this year, so using it to generate €48,000 worth of savings is a welcome relief in a low price year.

Credit to the Whytes

Full credit must go the Whyte brothers for leading the way in this venture. There was no definite proof that this system would work until it was made to work. The combined skills of the brothers and their sons has helped to pave the way for others to realistically consider the change from oil to renewable fuel.

Removing the diesel requirement from drying goes some of the way to improving the carbon footprint of wheat, but its greater benefit would be in decreasing the cost of drying, which can be highly significant in this country in wet years.

Hats off.