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Auckland Zoo is meeting the unusual green challenges of keeping animals such as sea lions and orang-utans.
The zoo - a big water and electricity user that once sent all its rubbish to landfill - has set goals since 2001 to improve its environmental performance.
Among new initiatives already proving their worth has been the installation of new systems to reduce power consumption of the sea lion and penguin enclosure.
Tess Doogue, the zoo's environmental co-ordinator, said the exhibit used to suck up nearly all the power coming into the zoo to create a mini-ocean environment involving cooling, pumping and injector systems.
The water required refrigeration to keep the temperature constant with filtering and cleaning needs.
After an energy audit and expert advice, pipes were insulated and specialised equipment installed to make better use of the electricity, only now accounting for about half the zoo's energy consumption.
Ms Doogue said the different types of animal waste had also been a problem as faeces from animals contained bugs that were not destroyed in most composting facilities.
However, such waste was now sent to a composting outfit in Tuakau large enough to generate enough heat to kill the bugs. It could also decompose bamboo scraps left by the elephants.
Ms Doogue said in the decades after the zoo opened in 1922, there had not been any measuring of its water and energy use.
The zoo turned out to be one of the top-10 water-users in Auckland.
All its refuse went to landfill and wastewater from the animal enclosures was hosed into Motions Creek.
Ms Doogue said the amount of waste now sent to landfill was well below 1992 levels, having fallen to less than 3 tonnes each month.
The bagging and selling of animal manure alone had diverted 3sq m a week of droppings from landfill.
Water use had halved and its quality leaving the zoo downstream averaged what it was upstream.
Energy use had been reduced by one-third, she said.
An industrial-size worm farm, using staff and cafe food scraps, and water tanks were installed in 2004.
Ms Doogue said the zoo had resumed voluntary water-quality monitoring and had cut back on chemical use.
The zoo's new conservation medicine centre was constructed to be energy-efficient and provide water collection off the roof.
Ms Doogue said a grid of rat traps was suggested to cut back on poison, and staff would experiment with spreading tiger urine around the zoo border to help keep rodents at bay.
They were also looking at growing animal food supplies and the potential for some on-site power generation.
