The organisers of next year’s 2024 Paris Olympics claim they will slash emissions in half and make a “positive contribution to the climate”.
But environmental groups have slammed this as “misleading”.
The climate toll of the Olympics has long overshadowed the games, which demand massive infrastructure, international travel and strains on resources.
So will the 2024 Paris Olympics really be sustainable?
How 'green' will the Paris Olympics be?
"We want to show that we can do these Games with half the emissions," says Paris 2024's director of environmental excellence, Georgina Grenon.
The organisers claim the event will emit around 1.6 million tonnes of CO2 equivalent, compared to the 3.5 million tonnes average from London 2012 and Rio 2016.
Emissions are broken down into travel, construction, and operations including accommodation, security and catering.
Paris is limiting its construction footprint by using existing or temporary infrastructures for 95 per cent of its needs. Many of these sites have been chosen for their public transport links, which organisers hope will curb emissions.
Electricity will come from renewable sources where possible. ‘Low carbon’ menus for spectators will offer dishes with less meat.
"Within the limits of what is technically feasible in 2024, we will have made every effort to reduce, reduce, reduce," Grenon says.
But the strategy also relies heavily on carbon offsetting, a problematic solution that environmental campaigners say doesn’t address the root of the problem.
Can carbon offsetting make the games ‘climate positive’?
The organisers of Paris 2024 say carbon offsetting will cement the Games as a world leader in sustainability.
"By offsetting even more CO2 emissions than those we will emit, we will become the first major sporting event with a positive contribution to the climate," they claim.
Offsetting involves investing in green projects, such as reforestation, that are designed to make equivalent cuts to CO2 in the atmosphere.
However, the impacts of these projects are difficult to qualify, vulnerable to changes over time and distract from more sustainable options, according to independent watchdog Carbon Market Watch. They can also have a negative impact on farmers and Indigenous people.
The organisers of the Olympics say they will rigorously assess their carbon offsetting partners. This option will only be used “for the emissions that we cannot reduce or avoid,” Grenon adds.
Sports ecology expert Madeleine Orr, who is a professor at the UK’s Loughborough University, says offsetting is an “acceptable option” but draws the line at calling the games “sustainable”.
"Even if they do everything right, a big international event can't be perfectly sustainable," she says. "The most sustainable event is the one that doesn't happen.”
Lindsay Otis Nilles of Carbon Market Watch agrees.
“To say that an event has a positive impact on the climate is misleading,” she says.
“The event itself generates greenhouse gases that are bad for the climate. The financial support of the organisers to external projects does not change this.”
How will Olympians keep cool without air conditioning?
Organisers are planning to install an underground water-cooling system beneath the Athletes Village. This will be similar to the one that helped the Louvre stay cool during last summer's heatwaves.
In anticipation of hot weather, organisers have been studying heatwaves block by block in the Athletes Village. They have simulated conditions in the parts of the accommodation most exposed to the sun and have tested the effectiveness of the cooling system. The objective is to keep the indoor temperature between 23 and 26 degrees Celsius.
The geothermal energy system will ensure that the temperature in the athlete apartments in the Seine-Saint-Denis suburb does not rise above 26C at night, says Laurent Michaud, the director of the Olympic and Paralympic Villages.
In addition to the underfloor cooling, the insulation built into the buildings will enable residents to keep the cold obtained during the night throughout the day.
Olympic committees will have the option of setting up their own AC units in specific cases and on condition that the devices comply with technical criteria.
What will happen to the Athletes Village after the Games?
The Athletes Village will be located next to the River Seine in the north Paris district of Seine-Saint-Denis.
For two months between July and September 2024, it will host 15,600 athletes and sports officials during the Olympics. It will then host 9,000 athletes and their supporting teams during the Paralympics.
After the games, the 50-hectare site will become a zero-carbon, eco-friendly residential and commercial neighbourhood with 6,000 new inhabitants - the first ones moving in as soon as 2025.
Could the Olympics do better for the environment?
In a study published in the journal Nature in 2021, researchers laid out three actions that could make the Olympic Games more sustainable.
“Significantly reduce the size of the event, rotate the Games between the same cities, and implement independent standards of sustainability,” the researchers recommended.
Orr also envisions a downsized event, with fewer spectators flying in from afar. By reducing “the size and scope of the event”, less infrastructure and waste would be required, she argues.
"The world loved watching Tokyo  and Beijing , even without the fans," she adds. If viewers were to tune into TV broadcasts rather than travelling to the Games, they could be more sustainable.