Five people have chained themselves to a gate outside a Fonterra factory in Canterbury, protesting the co-op's use of coal.
The protesters - three grandmothers, a student and a farmer - have been joined by another 19, says Coal Action Network Aotearoa, which organised the demonstration at Fonterra's Clandeboye factory.
"Coal is the worst fuel in terms of changing the climate," said protester Jeanette Fitzsimons, former co-leader of the Green Party.
The group are wearing t-shirts and carrying signs emblazoned with the phrase 'Fonterra quit coal'. They've dumped a pile of woodchips in front of the gate.
"Fonterra is our second-largest user of coal and this factory burns 180,000 tonnes of coal a year," said Ms Fitzsimons.
"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."
The group's targeting Fonterra because it's "propping up the mining industry".
"Coal mines around the country are being reopened and extended because of Fonterra's addiction to coal," says farmer Mike Dumbar. Mr Dumbar owns a farm which Solid Energy tried to buy a few years ago - he refused to sell because of his opposition to coal.
Fonterra said it has had an "ongoing dialogue" with Coal Action Network Aotearoa, but didn't directly comment on Monday's protest.
"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," the co-op said in a statement.
"As a responsible corporate citizen, we too believe a transition away from coal will be the only sustainable future for dairy production."
The others chained up are Auckland Coal Action's Jill Whitmore, Coal Action Network Aotearoa's Rosemary Penwarden and student Charlie Montague.