Wellington  - Four activists from the Greenpeace environmental organization were arrested Tuesday as they tried to shut down a New Zealand coal mine supplying the world's biggest milk processing plant.

Three women and a man from Greenpeace blockaded gates and chained themselves to an excavator at Solid Energy's New Vale Mine, near Gore in Southland, in a bid to cut off coal deliveries to the Fonterra dairy co-operative factory nearby.

Greenpeace spokesman Simon Boxer said the mine's lignite coal, "one of the dirtiest fossil fuels," was used at the plant, which was recently expanded to increase its fuel requirements by 60 per cent.

Greenpeace recently launched a campaign against Fonterra, the world's biggest exporter of dairy products, accusing it of being the biggest obstacle to New Zealand doing its bit to combat climate change.

"Fonterra always goes for the cheapest alternative like dirty lignite coal for energy or unsustainable palm kernel, grown at the expense of Indonesian rainforests, for animal feed," Boxer said.

"This is being driven by its intensification of dairying in New Zealand. It would be in Fonterra and New Zealand's interests to preserve the land and our clean, green brand."

Boxer said Fonterra, which is owned by nearly 11,000 farmer- shareholders, was one of the biggest coal users in New Zealand with eight of its milk processing plants burning approximately 450,000 tonnes a year. (IANS)