Miscanthus growers have been damned by the lack of a solid and profitable market for their perennial crop. Many have quit production because of low yields and the absence of local markets.
Quinns of Baltinglass were instrumental in driving the planting of the crop over the past decade and they have also been very active in trying to encourage demand for the crop, especially in the heat markets.
The fact that the crop has been dogged by low yields and poor market demand has impacted on its potential profitability. Up to now, biomass crops have needed initiative and incentive at government level and this has not been forthcoming. The value of these crops has never really been tested. And while big biomass users like Edenderry Power are using a small amount of the crop to produce electricity, this crop does not suit this facility.
Much progress has been made on the husbandry of miscanthus. Seeding rates have been increased using fresher and better-quality rhizomes to ensure a full crop from the word go. It is now accepted that the crop needs good land and good fertility to produce to its potential and this includes the addition of fertilizer. Weed control is critical for the first few years of growth.
Much less progress has been made on the market side. A renewable heat incentive may stimulate the use of this and other energy crops but this is still not in place, despite a number of years of promises.
In the knowledge that the crop could be extinct by the time government action is taken, Quinns have been active in trying to encourage local uses for the crop.
A recent open day at Patrick Nolan’s yard in Thornhill, Tullow, revealed a new practical use for miscanthus. Patrick recently installed a 2.5MW Graso burner which uses miscanthus to generate heat for his continuous flow grain dryer. This is similar in principle to the unit installed by Whyte Bros in the Naul in Co Dublin.
The miscanthus burner now uses roughly 2,000 8x4x3 bales to replace about 300,000 litres of oil to dry approximately 40,000t of grain for Quinns. The boiler is brick lined on the inside to protect it from any corrosive tendencies related to the fuel source and it indirectly heats air which is blown from the burner to provide heat to the continuous flow dryer.
Fuel usage depends on the amount of moisture to be taken from the grain and the dryness of the bales. In general a two-bale load lasts about 1.5 hours. The temperature in the burner runs at 650-700°C but it can get up to 1,000°C. This indirectly heats other air which is transferred to the dryer so there is no risk from exhaust fumes or other substances being transferred to the grain. The air going into the dryer is kept at 110°C, but this can be pushed up to 130° if necessary.
Explaining how the system works, Conor Bruton, who is the Irish agent for this Polish burner, said that grain coming off the dryer is about two degrees lower than if an oil-fired burner was used to provide the same moisture drop. This, he said, is because the air flow is consistently at the same temperature all of the time while temperature fluctuates in an oil-fired burner.
New fuel
This is the first Graso unit to be fuelled by miscanthus, so the project was very much a journey into the unknown. There were real concerns about the potential for heat output, the corrosive nature of the fuel, its potential to clinker in the burner and the volume of ash likely to be produced. Well it seems like all of these concerns proved to be unfounded.
A level of clinkering does occur but this seems to be very brittle and virtually dissolves again once new bales are added and the heat level increases. And the quantity of ash produced is extremely low, much lower than had been anticipated. The material virtually burned out to nothing in the heat.
The corrosive power of miscanthus is very low in this burner as there is little or no contact between the fire and metal parts.
Perhaps the biggest surprise was the heat output. This proved to be even higher than that generated from wheat or rape straw and is estimated to range from 3.5-4.0kW/kg as opposed to around 3.25 to 3.75kW/kg from wheat and rape straw. This meant that the heat output was over 15% higher than had been anticipated.
The burner that was installed has manual front loading through an open door but it is fitted with automatic ash removal. However, it will soon be fitted with an automatic loading system which will remove the need for the very regular fuelling of the burner. This will involve a moving platform to carry a big number of bales towards the burner and this may only need to be reloaded a few times a day for its 24-hour working window.
The unit is fitted with a heat recovery unit to remove much of the heat from the exhaust. It is estimated that this is adding an additional five degrees to the air temperature leaving the burner. An exhaust scrubber is also now being fitted to remove any undesirable substances from the exhaust.
David Tyrrell from Quinns said that miscanthus at €80/t is roughly equivalent to diesel at 21c/litre and diesel is still significantly above this level of cost. On balance, the suggested payback on the investment is likely to be under three years. And miscanthus also provides a net saving to the economy in terms of carbon mitigation as a 6.75t/ac dry crop provides an alternative to 2,700 litres of diesel (ie a swop between fossil fuel and renewable).
Minimise transport
The objective is to find local markets for the crop to minimise transport costs. For this reason, local uses need to be established. But there is also a need for local biomass assembly facilities where harvested crops can be taken for storage and drying.
The bales used in the Nolan dryer are about a year old and they have been drying out for that time – the dryer the bale, the higher its heat value.
Paddy O’Toole of Quinns said that it is important to find ways to use the crop without the need for further processing, as this tends to take value from the primary producer.
Miscanthus is proving to be a very useful and cost-effective fuel source for grain drying.A 2.5MW bale burner is in use to provide a heat source to dry grain outside Tullow.A 6.75t/ac crop produces a fuel equivalent of 2,700 litres of diesel.The crop needs to be stored post-harvest to enable it to dry out.
Miscanthus growers have been damned by the lack of a solid and profitable market for their perennial crop. Many have quit production because of low yields and the absence of local markets.
Quinns of Baltinglass were instrumental in driving the planting of the crop over the past decade and they have also been very active in trying to encourage demand for the crop, especially in the heat markets.
The fact that the crop has been dogged by low yields and poor market demand has impacted on its potential profitability. Up to now, biomass crops have needed initiative and incentive at government level and this has not been forthcoming. The value of these crops has never really been tested. And while big biomass users like Edenderry Power are using a small amount of the crop to produce electricity, this crop does not suit this facility.
Much progress has been made on the husbandry of miscanthus. Seeding rates have been increased using fresher and better-quality rhizomes to ensure a full crop from the word go. It is now accepted that the crop needs good land and good fertility to produce to its potential and this includes the addition of fertilizer. Weed control is critical for the first few years of growth.
Much less progress has been made on the market side. A renewable heat incentive may stimulate the use of this and other energy crops but this is still not in place, despite a number of years of promises.
In the knowledge that the crop could be extinct by the time government action is taken, Quinns have been active in trying to encourage local uses for the crop.
A recent open day at Patrick Nolan’s yard in Thornhill, Tullow, revealed a new practical use for miscanthus. Patrick recently installed a 2.5MW Graso burner which uses miscanthus to generate heat for his continuous flow grain dryer. This is similar in principle to the unit installed by Whyte Bros in the Naul in Co Dublin.
The miscanthus burner now uses roughly 2,000 8x4x3 bales to replace about 300,000 litres of oil to dry approximately 40,000t of grain for Quinns. The boiler is brick lined on the inside to protect it from any corrosive tendencies related to the fuel source and it indirectly heats air which is blown from the burner to provide heat to the continuous flow dryer.
Fuel usage depends on the amount of moisture to be taken from the grain and the dryness of the bales. In general a two-bale load lasts about 1.5 hours. The temperature in the burner runs at 650-700°C but it can get up to 1,000°C. This indirectly heats other air which is transferred to the dryer so there is no risk from exhaust fumes or other substances being transferred to the grain. The air going into the dryer is kept at 110°C, but this can be pushed up to 130° if necessary.
Explaining how the system works, Conor Bruton, who is the Irish agent for this Polish burner, said that grain coming off the dryer is about two degrees lower than if an oil-fired burner was used to provide the same moisture drop. This, he said, is because the air flow is consistently at the same temperature all of the time while temperature fluctuates in an oil-fired burner.
New fuel
This is the first Graso unit to be fuelled by miscanthus, so the project was very much a journey into the unknown. There were real concerns about the potential for heat output, the corrosive nature of the fuel, its potential to clinker in the burner and the volume of ash likely to be produced. Well it seems like all of these concerns proved to be unfounded.
A level of clinkering does occur but this seems to be very brittle and virtually dissolves again once new bales are added and the heat level increases. And the quantity of ash produced is extremely low, much lower than had been anticipated. The material virtually burned out to nothing in the heat.
The corrosive power of miscanthus is very low in this burner as there is little or no contact between the fire and metal parts.
Perhaps the biggest surprise was the heat output. This proved to be even higher than that generated from wheat or rape straw and is estimated to range from 3.5-4.0kW/kg as opposed to around 3.25 to 3.75kW/kg from wheat and rape straw. This meant that the heat output was over 15% higher than had been anticipated.
The burner that was installed has manual front loading through an open door but it is fitted with automatic ash removal. However, it will soon be fitted with an automatic loading system which will remove the need for the very regular fuelling of the burner. This will involve a moving platform to carry a big number of bales towards the burner and this may only need to be reloaded a few times a day for its 24-hour working window.
The unit is fitted with a heat recovery unit to remove much of the heat from the exhaust. It is estimated that this is adding an additional five degrees to the air temperature leaving the burner. An exhaust scrubber is also now being fitted to remove any undesirable substances from the exhaust.
David Tyrrell from Quinns said that miscanthus at €80/t is roughly equivalent to diesel at 21c/litre and diesel is still significantly above this level of cost. On balance, the suggested payback on the investment is likely to be under three years. And miscanthus also provides a net saving to the economy in terms of carbon mitigation as a 6.75t/ac dry crop provides an alternative to 2,700 litres of diesel (ie a swop between fossil fuel and renewable).
Minimise transport
The objective is to find local markets for the crop to minimise transport costs. For this reason, local uses need to be established. But there is also a need for local biomass assembly facilities where harvested crops can be taken for storage and drying.
The bales used in the Nolan dryer are about a year old and they have been drying out for that time – the dryer the bale, the higher its heat value.
Paddy O’Toole of Quinns said that it is important to find ways to use the crop without the need for further processing, as this tends to take value from the primary producer.
Miscanthus is proving to be a very useful and cost-effective fuel source for grain drying.A 2.5MW bale burner is in use to provide a heat source to dry grain outside Tullow.A 6.75t/ac crop produces a fuel equivalent of 2,700 litres of diesel.The crop needs to be stored post-harvest to enable it to dry out. 
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