Storage of Fruit

From conceptual idea to construction

Negotiation support
and advisory services



Rent a ULO-cell
(Ultra Low Oxygen) in Vittsjö (South Sweden)

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Turn-key construction of ULO-storage facilities that are built
for the future.

Saarloos builds turn-key ULO-storage facilities and can even install solar panels for a more economical and environmental-friendly operation. We offer support during a learning period during which you as a fruit grower can learn to operate the total facility on distance from your office where you, by operating the system on an ipad or computer, will have control over the balanced atmosphere in the ULO- storage facilities. This will almost illuminate the risk that a harvest is damaged or destroyed.

The smallest recommended size of a ULO-cell has a size of between 70.000 to 80.000 kg apples. This is in order to keep the ULO-levels stable which is more difficult when the ULO-cells are smaller. Many fruit growers choose a facility with ULO-cells that can store 120.000 to 150.000 kg.

The estimated lifetime of a ULO-cell built by Saarloos is approximately 50 years. These cells are built for the future, as these are capable to also operate with even lower ULO-levels than the levels which are used nowadays. Saarloos ULO cells can even be used for DCA (Dynamic Controlled Atmosphere). This system is rather new on the market and is developed in such a manner that the system automatically regulates the different levels in the atmosphere in every cell according to the condition of the stored fruit.

If and when you as a fruit grower in the future decide to sell your company, the value will have increased significantly if it has a ULO-storage facility.

Some clients choose to contract a number of different companies for the construction of different segments of the facility. We also offer our services to construct one or some specific segments the facility, but we want to point out that in the past we have seen problems arise with overall coordination, construction integrity as well as with less experienced construction/engineering firms, which could result, as an example, in (gas) leaking floors. It is of course  possible that the total investment costs are lower if and when using a combination of  different constructing / installing companies for the different segments and installations of the facility, but the overall risks increase and the lifetime of the facility could be less.

  Hereunder we describe the various segments and installations which together form a complete ULO facility:


Foundation and floor

Both foundation and floor are specially constructed in order to be guaranteed gas and air tight. When other companies have built this part of the facility, it has happened that it is not gas-tight. Because of the ULO-facilities’ extreme conditions with higher than normal pressure and lower than normal pressure, the floor has to be constructed in a specific manner: differently compared to regular floors in storage facilities. During its entire lifetime, the ULO-storage facility has to be gas tight, which is a prerequisite in order to make the complete system function correctly. If the floor is leaking, there is a risk that the entire facility needs to be demolished in order to construct a new foundation.

Saarloos has more than 30 years of experience and we recommend that we build the floor, the roof as well as the walls. This approach will provide the fruit grower with a facility which can be operated for many decades in an effective and problem free manner.


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Insulation cell

The walls and ceiling should, like the floor, be gas tight. Saarloos imports its wall segments from Germany. These wall segments consist of insulation foam which can handle the considerable pressure fluctuations (higher and lower) which happens when a ULO-cell is in use. Competitors in the market often use cheaper wall segments of the same material, but the difference is that these are less gas tight and don’t insulate as well, which adds to the risk that cracks develop which causes the cell not to be gas tight anymore.

It happens that the wooden storage-boxes are not properly cleaned, or that an apple infected by fungus is in the storage. If this happens, the walls and the ceiling are exposed to the fungus where it starts growing. Saarloos ULO-storage facilities are built with the best products on the market which avoids that this is happening. However, we cannot avoid fungus entering the facility on tree boxes and therefore we recommend to instead use plastic boxes. The risk of fungus growing on the boxes is considerably lower and the lifetime of plastic boxes is considerably longer than wooden boxes.


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Rämna Fyllning

In order to insulate the walls even better, Saarloos' own product called "Rämna Fyllning" is used to cover all the joints and seams. Rämna Fyllning consists of a substance which looks like ordinary paint, but is specially developed to insulate a ULO-cell in an effective manner. If a ULO wall is damaged, this can often be repaired by covering it with Rämna Fyllning. This is why we recommend to fruit growers to always keep a tin of Rämna Fylling stand by in the facility.

The latest trend in the ULO-world is to use an even lower oxygen level. The cells that we have been constructing 20 years ago are still of such a high quality that these can be used with the newer, lower oxygen levels.


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The doors which we install are manufactured in the Netherlands by Salco. We have chosen Salco doors because we do not want to compromise on quality. Saarloos imports fully assembled doors to ensure these to be gas proof. In this way, by importing fully assembled doors, Salco warrants the quality of its own product.

When competitors claim that they are installing Salco doors, this is only partially true. What they are in fact doing is that they only order the frames of the doors from Salco, but use the same low budget-quality wall segments that they use for other parts of the facility, and fit these into the doors. These bring the same problems as we mentioned before under the section "roofs" and "ceilings".

The doors can be operated by a remote control in order to avoid that the person opening a door inhales dangerous gases.


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Cooling installation

This is a special cooling system that is built to store fruit during a longer period. The components of this system are manufactured in the Netherlands as well as in other countries. The system is assembled at the fruit growers' site of construction. A process with which Saarloos has over 30 years of experience.

It is essential that the cooling system has an integrated frost protection system to prevent that in the cells temperatures below the freezing point will occur. Saarloos installs this frost protection system by default, knowing that a complete harvest can be destroyed by frost damage.

Saarloos is using environmental friendly cooling liquids as well as ammonia in their cooling system.

Besides the cooling system, two more components are used to make a ULO-storage facility function.


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Oxygen (O2) scrubber

The first machine, a so called oxygen scrubber or nitrogen-generator, brings down the oxygen level. In the market there are different suppliers to choose from, but Saarloos is using the most stable vpsa which is very energy efficient. This machine, which is produced by Van Amerongen in Holland, requires least maintenance. If the oxygen levels are too high, fruits soften and the ripening process accelerates.


Carbon dioxide (CO2) scrubber

The other machine which is needed is a carbon dioxide-scrubber (CO2 scrubber). This machine decreases the carbon dioxide level in the air which is produced by the fruit. It operates without slipping in unnecessary oxygen. This machine is also manufactured by Van Amerongen.

The correct levels of carbon dioxide and oxygen are essential for a successful result. A too high level of carbon dioxide gives carbon dioxide damage on the fruit. For pears, this means these become hollow on the inside and brown on the outside. Apples get spots on the skin. If the oxygen levels are too low, alcohol is developed in the fruit.


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The operating system

These two scrubbers together with the cooling system are controlled on distance with an operating system which is installed either on a computer or an ipad. This system is manufactured by Aucxis which delivers systems for ULO-storage facilities all over the world. The Aucxis system guarantees the best storage results which lowers the risks to the minimum.


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In practice…

It is important to realize that when Saarloos receives emergency calls from its customers regarding operating problems, most of the time it is because the person operating the system is doing this in the wrong way. This is why Saarloos offers a training period during which the fruit grower can learn to operate the system. Saarloos has access to the same system, and if required Saarloos can interfere and make, on distance, adjustments in the fruit growers system. This is of course done in consultation with the fruit grower. This training period is very important as the wrong levels of a ULO atmosphere can damage an entire harvest. The machines can of course also be operated in the ULO-storage facility itself.

A ULO-cell can be opened not more than four to five times during a season. Fruit growers do this to sell parts of the stored harvest in different batches. When a ULO-cell is opened, it takes approximately four hours for the atmosphere to get back to "normal" (outside) levels before the cell can be opened.

When the oxygen level is back to normal levels, the planned batch can be taken out, and the cell can be closed. The different gas levels of the atmosphere in the cell(s) are according to a special schedule, brought back to ULO-levels. The time to achieve this varies, but it could take around 48 hours. The less the volume of fruit of vegetables in the storage cells, the more time it takes to get back to ULO-levels.

As mentioned before, it is important to store the right combination of varieties of apples, or other fruits or vegetables in the same cell. Saarloos is glad to give advice to you as a client on what works and what not. Please do not hesitate to contact us when you have any questions.

Saarloos offers its customers a number of different services. In our storage in the South of Sweden we have a complete range of spare parts that are required in order to be able to carry out immediate repairs as soon as possible.


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Solar panels

The large roof surface on a ULO-storage facility is very suitable for solar panels. Even other industrial facilities are very suitable for installing solar panels as these often also have large roof surfaces.

ULO-storage facilities are very suitable for the use of solar panels as the facility has different energy consumption levels during 24 hours. In daytime the sun heats up the facility and during this time of the day the cooling system is using more energy to keep the temperatures at the required low level in the cells. At nighttime the outdoor atmosphere is usually lower and as a result less energy is required for the cooling system. 

Solar energy can also be stored: By lowering the temperature in a ULO-storage facility with for example 0,2 degrees during the day when Solar energy is used. Therefore, during the night less energy of the electricity provider is required to keep the required temperature in the cells. The result is an environmental adapted and financially attractive solution.

We at Saarloos consider it important to constantly research new possibilities and developments, and to implement these in the daily practice. We keep ourselves up to date on the latest developments in the ULO and DCA sector in order to provide our customers the best possible products and services.

Saarloos offers to install solar panels and integrate these in the ULO facility.


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