Storage investment means customers get what they want

Investment in an advanced climatic control system for a large potato store 10 years ago resulted in so many benefits for the owners and their customers that additional older buildings have since also been upgraded. David Williams reports. 

“The stores aren’t hospitals – they are just sheds, and potatoes can never be better than when they enter the store,” stressed Christoper Lee – financial director for Cambridgeshire-based PJ Lee & Sons Ltd, one of the UK’s largest family-owned potato producers. “We can’t improve the quality of what was harvested in a difficult year or from marginal soils, but we do everything we can to minimize deterioration from grading until produce leaves our stores up to a year later. Potatoes are like grenades waiting to go off, but our storage investment is helping us manage the crop and its condition to ensure it meets specific customer requirements.”

The Lees have storage for up to 32,000t of potatoes and run four, four-row self-propelled harvesters with four automatic filling grading lines. Approximately 26,500t are sold for chipping and packing, across a wide range of customers nationwide and even to the Canary Islands. Storage includes 1,800t of seed potatoes kept at a satellite site. 

State-of-the-art 

In 2014, the Lee family invested in a state-of-the-art potato store to hold 12,000t of potatoes in seven cells under one roof. The building was equipped with a Dutch Omnivent climatic control system, utilising fans that suck air through the crop, rather than a traditional forced ventilation system where fans blow ambient air into the store. 

“We used to travel to Holland to buy seed every year, and quickly realised that the best potatoes were from growers with Omnivent storage systems,” continued Christopher. “That’s why we trusted Omnivent to design and supply the ventilation equipment for our new store. Air distribution is key, and the team’s knowledge and experience of how stores function is fantastic. If we ever have an issue, then we talk to the service desk which is staffed by experienced agronomists, and they immediately provide practical suggestions and solutions.”

Air distribution is key

Boxes are designed specifically for the suction ventilation system, and nylon curtains are draped over stacked rows of boxes creating a seal, and ensuring air is drawn through the crop. When treatments such as sprout suppressants are applied, these are effectively distributed throughout the produce rather than most ending up on potatoes near the top and sides of boxes as in traditional systems. 

Covid highlighted benefits

Christopher said that it was the Covid-19 restrictions that highlighted just how good the storage was. “Like other large-scale producers, our market shrunk at that time as people stopped eating out. We were concerned that potatoes stored for longer would deteriorate before they were needed, but at 13 months’ old, they were barely distinguishable from the new crop and our customers remained delighted with what we supplied. At a time when many growers ended up with a surplus, we sold everything available.”

Additional investment

From 2019, a programme of upgrading older stores was implemented, all with bespoke Omnivent-designed ventilation and climatic control systems. The existing stores weren’t suitable for conversion to suction ventilation, but all other aspects of storage are like the new store, and based on the assumption that crops must remain as close to harvested quality as possible right through to May or June the following year.

“Where yield losses during storage for the industry are typically 12–14%, we average 7% for the season. That’s a lot more saleable crop.”

Humidity control is described by Christopher as a ‘no-brainer’. “It’s brilliant. We can meet customer specifications without risking over-drying,” he explained. “That means we use less electricity and lose less weight, and we hold the quality better. Our weight loss trials are designed to be consistent and accurate. Rather than weighing similar empty boxes, we weigh the actual box that the potatoes were stored in to achieve our figures, as moisture from the crop will have transferred during storage to the wooden panels and frame.”

Safer and better

The stores are equipped with CO2 recuperation systems. “These pay for themselves, as we can keep stores locked up for longer after gassing and avoid letting ambient unconditioned air in,” said Christopher. “The CO2 sinks down to the bottom of the store, from where it is recovered and run through heat exchangers to minimise energy losses before being blown outside.”

“For health and safety, we used to open vents to remove the CO2 before working in stores but now we retain the gas in the stores and scrub the CO2 out with OmniRecups. An Ominivent bespoke gassing programme has been created for us, and this has been certified to meet stewardship requirements. Costs for our gas treatments rose to £650,000 for mint oil in the first year of use and are only slightly less now that we use DMN. We use the same, specified amount, but because the Omnivent system ensures the air and gas goes exactly where it is needed, the applications are reduced, and results are even better ensuring long term storability.”

Energy savings

Additional savings are achieved through reduced energy requirements. Omnivent specialists believe that if the air flow is correct and crops are stored properly then condensation shouldn’t be an issue. Christopher said that this has proved correct, and fans don’t operate for significant periods of time now in any of the family’s stores. Suction stores operate on average for just 6–8 hours in a 24-hour period, and the older stores with forced ventilation systems for around 12–14 hours per day – much less than before Omnivent control and distribution systems were installed. “Less running time means less weight loss and electricity use, and more potatoes to sell!” confirmed Christopher. Accurate real-time monitoring of each store as well as system activity is available through a smartphone app, which also allows control from anywhere with an internet connection.

A growing reputation

PJ Lee & Sons is enjoying increased demand for its produce, including from customers overseas. “The Omnivent system has really put our name on the map for produce quality, and we receive many more enquiries from buyers across the UK and abroad. The degree of climatic control available means that our onsite laboratory can work out the ideal storage conditions to achieve produce suitable for cooking in a particular way or within specific parameters. Supplying crop tailored to give best results means we can also achieve premium prices.”

Rapid return on investment

Christopher said that the Omnivent system costs approximately 20% more than conventional alternatives. “When we bought the new store, it was less about the cost and more about creating best conditions for preserving the ‘grenades’ in optimum condition for as long as possible. What the potato wants, the potato gets, and we agreed that if the Omnivent system paid for itself within 15 years then we would be completely satisfied. However, just 10 years on we have no doubts it has paid for itself already. I wouldn’t even consider consulting other suppliers if we invest in additional storage in future.”

This article has been originally written by David Williams, and published in the Farmers Guide edition of January 2025