Written by Chris Harrowell
Woolly four-legged lawn mowers are set to help Watercare cut its costs by more than $160,000 over the next decade.
The organisation, which manages Auckland's wastewater network, says that's how much it expects to save by using sheep to keep down the grass at its biological nutrient removal (BNR) facility in south Auckland.
The facility is part of Watercare's Māngere wastewater treatment plant.
Watercare environmental technician Liam Templeton says the 60 coopworth-breed ewes and lambs are on loan from Auckland Council.
The organisation has invested about $55,000 to install the necessary fencing, shelter, and water troughs for the animals.
"This whole block of land will become another BNR project in about 13 years as Auckland's population expands," Templeton says, of the 5.5 hectare site.
"We'll save about $164,000 in grass maintenance [costs over the next 13 years]."
Templeton says using the sheep was the brainchild of Watercare chief operations officer Shane Morgan. Doing so makes sense for environmental and economic reasons, he says.
"He [Morgan] had the idea to put the sheep on the land for a few reasons.
"We're not using a tractor [to mow the grass] so we're cutting down on the amount of fossil fuel we're burning through.
"The secondary element is the grass and carbon-catching.
The more the sheep have the first bite of the grass, it allows it to regrow and absorb more carbon dioxide from the atmosphere.
"There's also the health and safety side of it as there's less big machinery around."
Watercare spokeswoman Maxine Clayton says the sheep now on the site will eventually go "off to market" and will be replaced by new ewes and lambs.
She says they'll enable the organisation to cut back on the amount of pesticides it uses at the BNR facility given that "sheep are such fantastic weedeaters".
"We want to be energy neutral at the Māngere and Rosedale [wastewater] treatment plants by 2025.
"This [using the sheep] is part of the whole philosophy [of Watercare].
"There's a huge amount of research going on around what we can do with the biosolids [resulting from the wastewater treatment process] rather than put them on Puketutu Island."
Templeton says the sheep being used by Watercare are unique.
"Coopworth are a special type of sheep. They were developed by Lincoln University [in Canterbury] to be particularly fast-growing.
"I think they'll enjoy the pasture here, particularly because of the amount of clover on the land."
Clayton says Watercare is "very aware of health and safety regulations" regarding the sheep and their droppings.
"The sheep are being kept behind brand new fencing so they won't be able to jump or stumble into any active area of the plant.
"They won't be able to access any wastewater."