The Port of Tauranga has this year handled 49 imported containers of ammonium nitrate, the stored chemical which ignited at the port of Beirut in a massive explosion which has killed more than 110 and left thousands homeless.
But New Zealand's biggest port said long-term storage is prohibited at the port and the chemical has to be loaded out within 24 hours.
A port spokeswoman said the substance was destined for the mining, quarries and construction sectors. Most went to Auckland.
The Ports of Auckland also said ammonium nitrate had crossed its wharves, but only in small amounts and always in containers. The chemical must leave the port within 24 hours, a spokesman said.
Ammonium nitrate is used in fertiliser but New Zealand industry heavyweights Ravensdown and Ballance Agri-Nutrients were quick to dampen public concern in New Zealand following the Beirut explosion.
Ravensdown said it did not stock pure ammonium nitrate anywhere in New Zealand.
One of its products, CAN, has ammonium nitrate as an ingredient, which is classed as non-hazardous and non-flammable, the company said in a statement.
Ballance said it did not buy or supply ammonium nitrate as fertiliser.
"It is not imported and therefore there is no handling or storing of ammonium nitrate," the company said.
But the Tauranga port said it could come into the port either in containers with a maximum 400 tonnes per shipment or by break bulk - in drums or on pallets at a maximum 25 tonnes per shipment.
The port company generally only handled containerised ammonium nitrate. No break bulk material had been handled this year.
"There are strict rules about how it is stored on the ship and how it is unloaded to keep it separate from other cargoes and sources of ignition," the spokeswoman said.
The use of ammonium nitrate in New Zealand, including its import and storage, is regulated jointly by the Government's Environment Protection Agency and WorkSafe.
Neither was able to immediately respond to the Herald's questions about what it is used for in New Zealand and how it is policed.
Napier port said regulations did not provide for it to allow any amount of ammonium nitrate to be stored at the port.
Lyttelton Port general manager bulk cargo Paul Monk said the port, as a transitional facility, did not hold a storage licence for Class 1 hazardous substances so did not allow customers to store them there.
Fertiliser imported by its customers was not classified as dangerous goods, he said.
The port was not aware of any recent imports of ammonium nitrate.
According to the EPA website, under the HSNO Act, a hazardous substance is any substance that has one or more of the following properties, above specified levels:
- an explosive nature (including fireworks)
- ability to oxidise (i.e. accelerate a fire)
- acute or chronic toxicity (toxic to humans)
- ecotoxicity, with or without bioaccumulation (i.e. can kill living things either directly or by building up in the environment)
- can generate a hazardous substance on contact with air or water.
It says hazardous substances can have more than one hazardous property. For example, methylated spirits and petrol are flammable and toxic.
Ports of Auckland said in the last 12 months, it has had 25,700 units of various classes of hazardous goods pass across its wharves, including most of those on the EPA list.
"Some, like explosives, are the first off the ship, straight on to a truck and out. The least hazardous stuff can stay up to three days," said a spokesman.