Food waste is contributing to cause catastrophic climate change, research shows.
It has found as much as one third of all food is thrown away, and oozes greenhouse gases into the atmosphere as it rots.
Research in 2015 found New Zealand households throw away 122,000 tonnes of food a year.
That research is currently being updated to see if New Zealander's habits have changed since then.
Further research is under way into food losses from commercial premises.
The wastage in New Zealand happens despite solid efforts by many organisations to fight this very problem.
One such body is Freestore, which collects unsold food from city cafes and distributes it to needy people.
One of their workers is Richard Carter, a reformed alcoholic, 52, who wheels a collection trolley around town every afternoon, and has become a familiar face to cafe owners across the city.
"I just like helping out the community," Mr Carter said.
"When I was drinking, I didn't care about anybody, but since I have been sober for nearly six years, I thought, 'oh well, why not change'?"
Cafes across town give Mr Carter sandwiches, scones and other goodies that did not sell.
They are hygienically handled in tongs, and offered as free food to needy people each evening.
An organiser of Freestore, Alana Hathaway, said 100 to 120 people from many backgrounds would turn up for a feed.
"We have people who are travelling at the moment, people who are in inner city housing, people experiencing homelessness, students, or people who just need a bit of extra food after they have paid the bills.
"Anyone is welcome, there is no set demographic that we are aiming at, anyone is welcome."
Efforts like this come against a background of worry about the environmental impact of wasted food, as well as the social hardship faced by groups such as the homeless.
Three European think tanks, Climate Analytics, NewClimate Institute, and Ecofys, have found throwing away uneaten food has a huge environmental impact.
"Over a third of the food (the world) produces - about 1.3 billion tonnes each year - is wasted," said Yvonne Deng of Ecofys.
"If food waste were a country it would be the third largest emitter of greenhouse gases, with an estimated 2011 level of 3.5 billion tonnes of CO2 or other greenhouse gases each year."
She added only the US and China produced more greenhouse gases than global food waste.
The worst offenders were wealthy countries and the problem could triple by 2050.
The experts have found that wasted food caused climatic damage in two ways.
First, greenhouse gases were emitted from machines like tractors and from processes like ploughing the earth, to produce food that was not needed.
Second, food gave off carbon dioxide and methane while it was decomposing.
Despite the efforts of groups like Freestore, New Zealand's record wasn't good, according to Jenny Marshall of the Love Food Hate Waste campaign.
The organisation researched the contents of 1400 rubbish bins from a cross section of houses and came up with a startling figure.
"As a country, it was $872 million worth of food that people were throwing away uneaten," she said.
"We are thinking about bread, we are thinking, 'I have bought a roast chicken and I have only eaten half of it and I am throwing it out with the carcass'.
"It was perfectly good food, enough to feed the population of Dunedin for two years."
That research is currently being re-done for up to date figures.
In addition, there's further research into how much food is wasted from supermarkets, pubs and restaurants.
Globally, the think tanks recommend better use-by and best-by dates on food, and more efficient storage and distribution of food.
Re-use of food such as that practised by Mr Carter could help, so could feeding surplus food to animals.
Other campaigners say people often don't know how much money they're throwing away from wasted food, so timely publicity, and some political will, could help.