World Vision will this year focus on the refugee crisis with a new 40 Hour Famine backpack challenge to raise funds for those who shoulder the burden of the crisis each and every day.

Traditionally, participants would fast on water and barley sugars for the 40 hours, but this year the idea is to survive off a backpack filled with just the essentials: food, water and something to keep warm.

The money raised will be used to provide resources and establish safe spaces in Syria, South Sudan and their neighbouring countries - home to some of the world's most vulnerable children.

Of the 65.1 million people forced to flee their homes due to famine, conflict, and climate change worldwide, more than half are children, according to World Vision.

For the first time in its 42-year history, the campaign's spokesperson is someone who survived that exact trauma and found solace in Australia - former South Sudanese child soldier turned western Sydney lawyer Deng Adut.

Mr Adut, a refugee and the 2017 NSW Australian of the Year, will address 900 students at the campaign's national launch in Sydney on Tuesday in an effort to educate the next generation on the humanitarian crisis and to inspire change.

His message will also reach tens of thousands of young people via a live stream into Australian classrooms.

Mr Adut says the backpack challenge is a way for people, particularly youth, to assist the plight of child refugees who are forced to leave school and go in search of shelter and food, while at risk of being separated from their families.

"I did not have the chance to leave with a backpack - I was simply taken away," he said in a statement.

"But now today, as a lawyer, I carry a briefcase. There is always hope. I had hope because of the many people that helped me in my journey."

He said "collective hearts and minds" can achieve greatness through shared knowledge and "freedom of fear".

"I can't imagine a more honourable mission than to save a child's life. What more, when that mission is fulfilled by another child," Mr Adut said.

A 'Humanitarian Masterclass' series of videos will be provided to teachers and students ahead of the challenge.

It's hoped thousands of Australians will be sponsored to live out of their own backpacks and briefly experience the life of a refugee forced to leave everything else behind.

The 40 hour Famine Backpack Challenge will be held from August 11-13.

For details, contact: 40hourfamine.com.au.

© AAP 2017