The Olympics has sustainability as one of its three pillars, but it's accused of making big environmental promises without following through

Paris was the greenest games yet, but critics say until the Olympics stops becoming a tourist event, all the vegan food in the world won't negate its environmental harm.

The Paris summer Olympics is done and athletes, their supporters and spectators are returning to their far corners of the world.

Nearly 11,000 athletes from more than 200 countries, 400,000 accredited officials and coaches, and several million spectators... most of them flying home.

Paris was billed as the greenest games yet, with cardboard beds, locally produced vegan food, stadium seats made of recycled plastic and e-bikes to get around on.

Not all of this was appreciated by athletes, with some teams demanding more meat and eggs, and others bringing their own air conditioning units.

But the aims were good - to halve the carbon footprint of these games compared to Rio in 2016 and London in 2012. A big deal was made of using renewable energy, and only having to build two new venues (an aquatic centre and climbing venue) and two new facilities (a media village for journalists and athlete accommodation) for the event.

However the elephant in the room is air miles, with the biggest portion of greenhouse gas emissions from major sports events like this estimated to be travel. Some research suggests it accounts for between 50 and 70 percent of emissions, other work estimates it is up to 85 percent.

"A lot of sport, and a lot of sustainability endeavours in general, are accused of different hues of greenwashing in a sense of making big promises but perhaps not taking those actions," says Dr Chris McMillian, a professional teaching fellow in sociology at the University of Auckland.

"The Olympics and the Olympic movement is kind of at the forefront of a lot of sustainability measures in sport. But the accusation is that while they're communicating this and making big promises perhaps they're not following through as much as they can.

"We're still waiting for the final carbon accounting to come," he says.

McMillian points out though that sport is famously bad at quantifying its impact, and cities in the past have made promises during their bidding wars that have quietly slid away in the heat of the extravaganza to follow.

He says there's a suggestion that the Olympics is actually becoming less sustainable over time, as more events are added, bringing more athletes, supporters and fans from around the world. …

Go to this episode on rnz.co.nz for more details