The Paris Olympics says it was far less polluting than recent Games but is not claiming to have been "carbon neutral" despite funding projects to compensate for its emissions.

Organisers said this summer's Olympics and Paralympics generated 1.59 million tonnes of climate-warming carbon dioxide, from the food athletes ate and construction of their rooms to flights that spectators took and energy that powered events.

According to a French government carbon-impact calculator, 1.59 million tonnes of CO2 is equivalent to driving a car 182,675 times around the globe or 898,305 return flights between Paris and New York.

Still, Paris Games organisers said they more than met their goal of slashing the Olympics' pollution footprint by half - announcing a 54.6 per cent reduction in CO2 emissions compared to the London Olympics in 2012 and the Rio de Janeiro Games in 2016.

Paris organisers said thinking about carbon emissions far in advance of the Games and setting a reduction target were key. Those who led the task of planning and organising the mega-event were given carbon budgets. Measures to slash emissions were built into plans from the start.

"To change things, we had to reinvent," said Georgina Grenon, the Games' director of environmental excellence.

Just as athletes seek ways to shave milliseconds off their times, Paris organisers sought not just big carbon savings - by building just one competition venue specifically for the Games - but smaller ones, too.

The Olympic cauldron used electricity and LED spotlights to give the impression of being ablaze. That made it 300 times less polluting than if it had burned gas, Grenon said.

Even Olympic medals included recycled materials, with each embedded with a reused chunk of the Eiffel Tower.

Electricity powered 98.4 per cent of the Games' energy needs and organisers said a purchasing agreement they signed with power supplier EDF ensured it was all solar- or wind-generated.

In selling 12.1 million tickets, Paris set attendance records. But transporting spectators to the French capital and to events came at an unexpectedly large carbon cost.

Transport had been expected to account for about one-third of Paris' carbon footprint, but organisers said it ended up accounting for 53 per cent.

"We were a bit victims of our success, because we sold many more tickets than initially estimated," Grenon said.

Organisers said they are spending just over 12 million euros ($A19.8 million) on projects in Africa, Asia, Central America and France that aim to compensate for the Games' 1.59 million tonnes of carbon emissions.

The money is funding tens of thousands of less-polluting cooking stoves and access to water in Nigeria, Congo, Kenya and Rwanda, solar power in Senegal and Vietnam and forestation in Guatemala, Kenya, Senegal and France, organisers said.

But Grenon said while the projects aim to compensate for emissions, Paris won't label its Games "carbon neutral" because that can be misleading.

"It can give the impression that there is no impact when there is an impact," she added. "There was an impact but we treated it and, most of all, we reduced it."