The Conservatives are the only party not buying offsets for the carbon footprint of their leader's tour during the federal election campaign.

The four other major parties are buying offsets from established Canadian companies. The Bloc Québécois and the New Democratic Party are purchasing theirs from Planetair in Montreal, while the Liberals and Greens are working with Carbon Zero in Toronto.

When asked about the decision not to buy offsets for the campaign tour, the Conservatives replied in a email to CBC News that they will focus their environmental efforts on clean energy projects across the country, such as the Lower Churchill hydroelectric project in Labrador.

Conservative Leader Stephen Harper has pledged a re-elected Conservative government would commit to a loan guarantee or equivalent financial support for the $6.2-billion project, and the Tories said it would reduce carbon emissions by up to 4.5 million tonnes each year and "provide significant environmental benefits."

CBC News's Environmental Unit performed an informal calculation  of the transportation footprint of each leader's tour. The CBC found the NDP, Conservatives and Liberals had similar results, with all three leaders well over 120 metric tonnes of greenhouse gas emissions in the first 10 days of the campaign.

The Bloc and the Greens were both under five tonnes. CBC News will update this calculation weekly throughout the election

The stark difference can be attributed to air travel. The Conservatives and NDP have both racked up over 12,000 kilometres by plane, while the Liberals have travelled nearly 10,000 kilometres in the air.

"One of the things about air travel, as opposed to other forms of greenhouse gas pollution, is that climate scientists show it actually has higher impacts than just the straight emissions because it's being emitted higher up in the atmosphere," said Clare Demerse of the Pembina Institute, an environmental policy research group.

Duceppe buses; May rolls in a Prius

So far, the Bloc has only travelled by bus. That is one of the benefits of only having to run in one province. While the Greens are a national party, Leader Elizabeth May is focusing all her efforts in the British Columbia riding of Saanich-Gulf-Islands, where she is a candidate. It also helps that she is driving a 2007 Toyota Prius, a hybrid car.

But both parties are purchasing offsets.

Dan Fraleigh, director of operations at Carbon Zero, told CBC News that his company is finding consumers are buying offsets a lot more since the last federal election.

"Moreover, we find that consumers have become the market driver for other entities like corporations or political parties," he said.