No antifreeze for RHP certified load 

21 december 2017

RHP certified substrate components and substrates are to be transported in a way that its purity and quality requirements are maintained. The loading space needs to be clean before loading RHP certified products and contamination needs to be avoided at all time. In the winter period with a chance of temperatures below zero, here is some safety advice to prevent the load from freezing in the truck.

Sometimes antifreeze is considered to use in order to prevent the substrate components or substrates from freezing onto the sides of the loading space. However, antifreeze is dangerous for plants and therefore use is not permitted. If really necessary, there are alternatives. For transport of substrate components and substrates with the RHP quality mark, the use of the horticultural fertilizers urea (up to -10°C) or calcium nitrate (colder than -10°C) is advised as safe, alternative antifreezing agents. These do not have an harmful effect on the load.

Up to -10°C: urea

With temperatures up to -10°C urea is suitable. Of all horticultural fertilizers this is the least corrosive. Depending on the temperature the right concentration can be chosen (see table).

Colder than -10°C: calcium nitrate 

Urea doesn’t work anymore during harsh frost with temperatures below -10°C. Then the horticultural fertilizer calcium nitrate offers a possibility. This salt is more corrosive than urea, so use it in a concentration as low as possible (see table) and rinse the truck well after transport.

RHP table urea calcium nitrate

Concentrations to follow with the freezing point of the solution for several temperatures.

Calculation examples

Practice shows that in a truck of 100 m3 approximately 5 litres of anti-freezing agent is used.

A couple of calculation examples:

  • With the application of a solution with 32,5% urea, in the case of a load of 65 m3, there is 5*480 gram/litre = 2400 grams urea / 65 = 37 grams urea per m3 = 14 mg per litre.

The total dosage is so low that it causes no problems for the load of substrate components or substrates in the truck. But the salts do concentrate on the outside of the load. To prevent this from staying this way, the load needs to be mixed well after transport. The used anti-freezing agent urea will then spread through the load and is diluted to an even, low level in the substrate component or substrate.

  • With the application of a solution with 39% calcium nitrate, in the case of a load of 65 m3, there is 5*640 gram/litre = 3200 grams calcium nitrate / 65 = 49 grams calcium nitrate per m3 = 49 mg per litre.

Here the same applies as with urea. The dosage is low, but the load needs to be mixed well after transport to dilute the parts where there was a high concentration.

The measurements of an average truck amount to approximately 100 m2 sides and floor. The outer layer of about 5 cm substrate component or substrate takes up the solution.

  • 100 m2 * 5 cm = 5 m3. For the example with calcium nitrate this would lead to a dosage of 640 grams per m3, so 0,64 grams per litre.

This is in itself a pretty high dosage and shows that it is important to mix the substrate component or substrate well after transport. Especially when we assume that most of the sprayed solution collects on the floor on the sides of the truck and causes higher concentration in the load in those areas especially.

Transport requirements

All transport requirements and cleaning actions for transporting RHP certified products are described extensively in Module 260 of the Product Certification Scheme RHP. Certified companies can access it at My RHP. When the requirements are not met, the RHP quality mark ceases from the moment of loading the truck. If you want to use other anti-freezing agents than the safe horticultural fertilizers urea or calcium nitrate, you will need to request exemption in time with RHP.

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