UPDATED 5.40pm A group of protestors have left a Fonterra dairy factory in South Canterbury, happy they've got their message across.

LISTEN ABOVE: Jeanette Fitzsimons spoke to Larry Williams

Five people chained themselves to the main coal delivery gate at the Clandeboye plant for more than four hours.

A second gate was also blocked by a protestor for a time.

They are urging the dairy giant to stop using coal.

One of those who took part was former Greens co-leader Jeanette Fitzsimons.

She told Larry Williams they left satisfied with the action after causing chaos for coal trucks, and speaking to a staff member.

"But we've made it really really clear that unless we see a reduction in Fonterra's coal use, and a transition plan to gradually convert their plants to other fuels, then we will keep on."

Fonterra is understood to use coal in the process of creating milk powder with protesters urging the company to use an alternative fuel, such as woodchips.

"Fonterra is our second largest user of coal and this factory burns 180,000 tonnes of coal a year," Ms Fitzsimons says.

"All of this ends up in our atmosphere, contributing to climate change. It's time for Fonterra to keep the coal in the hole and switch to woodchips instead.

"Fonterra's coal use is also propping up the mining industry - coal mines around the country are being re-opened and extended because of Fonterra's addiction to coal."

A Fonterra spokesman said the protest was not impacting operations and that the company had maintained an ongoing dialogue with CANA in recent years.

"(We) understand and share their position on coal," he said.

"Fonterra is committed to reducing environmental impacts across its operations through the use of new technologies and optimisation of our energy mix towards cleaner, more efficient forms of energy."

"We measure our performance based on energy intensity per tonne of product, and set the standard within the New Zealand dairy sector based on this metric."

The protest follows a CANA conference in Ashburton in Canterbury in which more than 50 campaigners from around the country held a two-day around the issues of Coal, Cows and Climate.