New chemical knowledge and new chemical legislations can cause phosphate fertilizers containing ammonium nitrate and other ingredients to be classified. These types of product might be classified as hazardous to humans and also to the environment.

Over the years ammonium nitrate fertilizers have been involved in several accidents that have influenced the legislation of transport, storage and handling. Decompositions during transport and in storage have caused release of toxic gases and hazardous situations.
United Nation has issued the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). The GHS is harmonized with the UN Recommendation on the Transport of Dangerous Goods – Model Regulation, regarding test methods and identifying hazards. Europe has adapted the European version of the GHS and issued the Classification and Labelling of Products (CLP).

The international UN ‘Recommendations on the Transport of Dangerous Goods’ (www.unece.org/trans/danger/danger.html) is adopted in international fertilizer transport legislation by IMO (shipping), ADR (road), RID (rail), ADN(R) (barges) and IATA (air) regulations. National and local regulations apply for storage of fertilizers. The SEVESO-directive gives guidance on storage volumes /risk assessment for hazardous products within the EU.

Straight Ammonium Nitrate (High nitrate fertilizer)

AN 33.5 is classified as an oxidizer (Class 5.1) by UN due to its high ammonium nitrate content. Special regulation for storage is given by national authorities. Yara ammonium nitrate based fertilizers pass the resistance to detonation test, and have very high resistance to detonation. When bagged fertilizers are involved in a fire, the bags may melt and break, but they will have insignificant effect on the fire.

Handling of spillage and reject material containing Ammonium Nitrate

Spillage from conveyor belts or from bags should be collected quickly, handled and sold as normal product if free from contamination and meeting the requirement of the fertilizer regulations. If not, the material shall be dissolved or be made inert. If seriously contaminated, product should be treated as a waste material, and hazardous material should be handled according to local legislation.
In addition to the CLP Regulation in Europe, storage of ammonium nitrate containing fertilizers are regulated under the COMAH (Seveso) directive. Some European countries like Germany and France have additional national regulations, TRGS in Germany, Code de l’environment in France, controlling the storage of these products. These types of national regulations are becoming more common and need to be checked locally.

Ammonium Nitrate in NPK

Ammonium nitrate in NPK fertilizers can decompose at high temperatures. Exothermic reactions cause evolution of heat and gases from the fertilizer after an initial period with decreasing pH. The rate of decomposition accelerates in the presence of chloride, organic substances and some metal ions – particularly copper (Cu²⁺). The decomposition is retarded in the presence of phosphate, carbonaceous material and high pH.
Some ammonium nitrate based NPK fertilizers exhibit characteristics of self-sustaining decomposition (SSD). SSD can be initiated by accidental heating (> 120°C) over time for some fertilizers. Such decomposition will continue after the heat source has been eliminated, and can be very difficult to extinguish. The decomposition is normally not dangerous in itself, but the released gas contains toxic components (e.g. Cl₂, HCl, NO_x).

Calcium Nitrate fertilizer

CN fertilizer contains approximately 15 % crystal water that minimises the oxidising properties of the material. Fertilizers based on nitric acid ammonium calcium are classified in GHS/CLP as “Acute Tox, 4 H302., Eye Damage/Irritation, H318”. The product bags are labelled according to the appropriate chemical regulations. No severe accident has ever occurred with CN fertilizer.

Urea products

Urea products are not classified as hazardous material according to (EC No. 1272/2008) , CLP) and the UN transport regulations, but are potentially dangerous because they can release ammonia if exposed to strong heat. Urea should not be mixed with other chemicals, mixing with Nitric acid may be particularly hazardous.

Buildings and areas for storage or handling of fertilizers should be secured properly to keep unauthorised people away. Fertilizers containing ammonium nitrate or other nitrates can be used to manufacture explosives, which has occurred in several terror attacks worldwide. The availability of such products is therefore restricted by law. Mineral fertilizer containing 16% or more ammonium nitrate is not available to the public. Only farmers and other professional users are given access to such products. (EU Regulation 1907/2006, REACH)
A simple rule of thumb is that if both the nitrate nitrogen (NO₃-N) and the concentration of ammonium nitrogen (NH₄-N) is 8% or higher, then the product contains more than 16% nitrogen in the form of ammonium nitrate.

Simple advice for preventing crime:
•   Store the mineral fertilizer in locked rooms
•   Cover the mineral fertilizer that must be kept outdoors
•   Check regularly if you lack the mineral, ie if something may have been stolen.
Do not sell fertilizers on to someone if you are not sure whether it will be used professionally.