A gas leak in the main supply line north of Taranaki forced Fonterra to shutdown 15 of its milk processing plants in the North Island, costing the company around $20 million a day in spilt milk.

All commercial customers from the King Country upwards, including the Bay of Plenty were forced to stop using gas, including hospitals, schools and essential services.

For dairy farmers in the Waikato, Bay of Plenty, and Northland the gas leak came at the height of the spring flush.

Fonterra’s tankers were collecting 30 million litres of milk a day but the company can only process about 5 million litres at the two coal fired processing plants at Waitoa and Te Awamutu.

Waikato Dairy farmer Neil Bateup told Country99TV news It is a difficult time for farmers who are having to dump milk, a costly, wasteful and potentially environmentally damaging exercise.

"Well obviously it’s a huge waste of money. I guess it will affect the whole industry in the end. We’ll be compensated, I guess, for the milk we send, but the total cost of it will come back onto farmers."

 Waikato District Council and Northland Regional Council are urging farmers to do all they can to keep milk out of waterways. Milk is very toxic and strips oxygen from the water.

Most farmers lack the capacity to hold milk on their farms for more than a few days and mass dumping may be the only option available to them.

Milk can be fed back to stock. It can be irrigated onto pasture, but has to be diluted with water. And it can be dumped into effluent storage ponds.

Neil Bateup said "We’ve got storage, we’ve got a storage pond so it’s going into there. We could probably handle two or three days, but after that I’m not sure what it will do to the storage pond. We’re in unknown territory."