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3 April 2012

There was an excellent attendance at the recent AHDB Potatoes storage forums held at Sutton Bridge and Herefordshire Racecourse.  Growers were rewarded with plenty of topical information to help improve their storage regimes. 

A surprising number of potato stores leak air making them energy inefficient and putting crop quality at risk from condensation.
Air leakage measurements, undertaken as part of a AHDB Potatoes project assessing the efficiency of stores and its impact on costs, have shown some stores suffer from significant leakage.  With energy costs ranging from £4/t to £7.50/t in recent seasons, tracking down problem areas and fixing them makes sense, Jon Swain of Farm Energy told the recent storage workshop.
“Many farmers may assume their stores are sealed, but invariably they will find holes when they do a leak test,” he said. “Stopping those leaks is important because they waste energy and cause condensation problems, which can lead to serious crop quality issues. They can also heighten the risk of CIPC loss and add to the farm’s carbon footprint.”
Jon has been working with Adrian Cunnington and Steve Saunders at Sutton Bridge CSR on the project and the research team tested eight stores for leakage. Several key areas were identified and their equivalent leakage area (m2) measured. This gives an indication of the leakage by adding together all of the leaks in the building and expressing this as the size of a single hole in the store wall.
The most common culprits for leaks were exhaust louvres (ranging from 0.05 to 0.45m2 per store). These were closely followed by inlet louvres and main doors, both of which had roughly the same leakage area of 0.1-0.35m2/store.
In the worst case the total leakage area for all sources was 5.5m2, though more typically it ranged from 0.5-1.5m2
When the problem areas were sealed, this typically halved the leakage area figure and in the worst case cut it by two-thirds.
“Overall, we estimated that up to 33% of a pre-pack store’s total energy consumption is wasted through leakage, and this could be up to 50% for a processing store. This can quite realistically be reduced to below 10% in best-practice stores,” says Jon.
Several methods can be used to identify leaks. “Specialist advisors can use thermal imaging equipment or smoke testing, which will do a thorough job, but even close inspection of suspect areas can reveal a lot” he notes.
Solar-powered electricity still makes good economic sense despite the on-going reduction in feed-in tariffs (FiTs), said Damian Baker, managing director of renewable specialist RenEnergy.
Although lower FiTs meant growers might have to wait longer before breaking even on their investment, those who used a large proportion of the power they generated would receive healthy paybacks, he said.
“Solar photovoltaics (PV) are still a great investment but people need to think more about how much electricity their business needs and what savings can be made, rather than how much money they can make from FiTs.”
FiTs for a typical farm-sized rooftop photovoltaic (PV) array of 50kW were recently slashed from 33p to 15p for each kWh of electricity generated, and were likely to fall by at least 20% in July and by 10% every six months after that, he added.
At current FiT levels, a store owner paying 10p/kWh who installed a 50kW array and used all the electricity from it (perhaps driving irrigation pumps in the summer when the store is not used) could expect to break even in year eight of the project’s 25-year life, he predicted. That assumed an overall cost of £90,000 installed, a 5% increase in electricity prices and 2.5% annual inflation.  
In year one, he calculated an 11% return, through an electricity saving of over £4100 and a FiT receipt of £6300, totalling £10,400. By year 25, the £90,000 investment would have turned into a £322,000 gain, he suggested.
Those using less than 100% of their electricity would still get a return, but it would take longer, Damian explained. Each kWh consumed on farm was effectively free, whereas exporting surplus power would only net about 4.8p/unit, halving the electricity saving and delaying breakeven by several years. The overall gain would also be reduced, he added.
Falling FiT levels would also reduce returns and growers considering installing PV should act soon to lock into the current rate, he advised. “FiTs were introduced as an incentive to bridge the gap between equipment costs and returns from generating electricity, not as a sole reason to invest. But they remain attractive - whatever level you secure will be guaranteed for 25 years and is index-linked.”
Growers also showed keen interest in the insights offered at the event by growers James Daw of WB Daw & Son and Tony Bambridge of B&C Farming. Emphasis was placed on good hygiene being key to storage success together with hands-on monitoring and daily data recording. 
Both growers recommended that only crops that meet market specifications should be stored, and that growers should invest in equipment to check quality such as absence of bruising, skin finish and fry colour. They noted that preventing just one or two rejections would pay for the kit. 
Tony advised anyone buying seed not to accept imprecise statements such as ‘a bit of blackleg’ and that they should ask questions so they know the percentage of a crop that has a particular problem.
Adrian Cunnington, head of Sutton Bridge Crop Storage Research, who organised the events, warned the audience about MRL exceedance.
“CIPC is our strongest solution but there is absolutely no room for complacency,” he cautioned.  “As it is crucial, we all have a responsibility to use it properly. To date, there is no alternative sprout suppressant for use in the potato processing and chipping sector. We must keep doing all we can to ensure best practice is followed throughout the industry or we will lose it.
“We need to be thinking about timing, about dosage and about ensuring we make an efficient application. Most of all, it is about the owner taking responsibility for his crop. It is not acceptable to absolve this responsibility to somebody else; if an MRL is exceeded the buck stops with the owner.” 
Commenting on the success of the forums, Adrian said: “Holding the forums in different areas of the country has proved very popular with levy-payers and both were extremely well attended. The workshops also provided an ideal opportunity for growers to ask questions on key issues of concern to their business.”
For other AHDB Potatoes events go to
For free storage advice call 0800 028 2111. 
Grower Gateway - Issue 3, 2012
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