The government's $525 million Green Army conservation initiative was rolled out on Saturday.

Launching the project at Carss Bush Park in Sydney's south, Prime Minister Tony Abbott and Environment Minister Greg Hunt said it would be the largest environmental workforce the country had mobilised. About 2500 young people were expected to join up this year to work on 250 projects around Australia.

Prime Minister Tony Abbott says about 2500 young people are expected to join up. Credit: Alex Ellinghausen

"It's six months of good work and good comradeship that you can come back and look at in the years ahead and say, 'I did that for my country'," Mr Abbott said.

"This is not a work for the dole project, I want to stress this. It's an environmental traineeship."