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LAST year’s Maui gas leak cost New Zealand dairies an estimated NZ$46m (US$37.5m) and caused them to scrap almost 50m l of unprocessed milk, according to a government investigation.

The leak cut off gas supplies to much of New Zealand’s North Island for five days last October, after a landslide damaged a major pipeline. The shortage forced much of the region’s energy-intensive milk processing plants to close down.

Fonterra, the dairy co-operative responsible for much of the country’s milk processing, scrambled to increase production at its coal-fired plants in the area, finding another 5m l/d of capacity. According to the report – written by New Zealand’s ministry of business, innovation and employment (MBIE) – however, this still “left a balance of approximately 30m l/d needing to be dealt with in some other manner.”

Phil Heatley, New Zealand’s energy and resources minister, says it’s “critical that the lessons learned from the outage are captured and acted on, so that gas consumers can be confident in our gas system.”

Faced with such a vast quantity of unusable milk, farmers were forced to spray it on to fields, tip it into ponds and even bury it underground. Suddenly halting milking can cause health problems to cows, but despite farmers’ best efforts the government says their “preparedness to manage milk storage and disposal would have been tested if the outage had continued for a prolonged period.”

Even those cows that do not suffer health problems after a break in milking run the risk of ‘drying off’ – ending their lactation cycle and becoming unable to produce milk for the rest of the season. This would have posed a major risk to the New Zealand economy, which relies on the dairy industry for more than 50,000 jobs and a quarter of its exports.

As well as an economic risk, the outage also posed an environmental threat, as milk is a powerful organic pollutant and removes oxygen from any water it’s discharged into, killing fish and other wildlife.

“The inability of dairy plants to process raw milk during the incident and the subsequent disposal of 48m l of waste milk could have caused a major environmental incident,” says the MBIE. “Fortunately, it appears that both factory and on-farm disposal of waste milk was reasonably well-managed during the incident.”

Nevertheless, both the government and Fonterra say they have launched plans to improve their contingency systems in the wake of the gas leak.