After returning from an around-the-world yacht race in 1987, where he found the world's oceans befouled with rubbish, Mr Kiernan organised a community event to help combat the spread of litter in public parks and waterways around Sydney.

And although that first event in Sydney Harbour was a great success, he says, he never could have anticipated Clean Up Australia's ultimate impact across the country, 25 years later.

"No, I had no idea we would gain the level of success we have," he says. "We had 40,000 volunteers turn up for Clean Up Sydney Harbour [in 1989], but it's just gone on and on from there.

"Australians have a great history of being very keen volunteers. They are used to rolling up their sleeves and getting stuck into a challenge, and that's what they've done with Clean Up Australia.

"It's a very simple idea, but the community has taken it up. They own it."

Since its inception in 1990, Australians have donated 28.75 million hours of their time to collect rubbish in the parks, rivers, streets and garden beds of the nation, ridding the natural environment of more than 30,000 tonnes of rubbish.

And on the 25th anniversary of the first Clean Up Australia day on Sunday, 526,268 volunteers cleaned up 6165 public sites, collecting an estimated 13,500 tonnes of rubbish.

Beth Hazell, 61, co-ordinated a Clean Up Australia event for Penrith Anglican College, where she is a teacher. Alongside about 200 others, Ms Hazell helped make Regatta Park in Emu Plains spick-and-span.

In her sixth year as an event co-ordinator, she says Clean Up Australia is a great way to instil in students the idea of community service and responsibility.

Elsewhere, 45-year-old Asquith resident Veronica Boccanfuso joined 10 others in helping to clean up the local Mills Park.

But what was the weirdest piece of rubbish collected?

Ms Hazell says she found tyres and shopping trolleys strewn across Regatta Park, while Ms Boccanfuso found old toys and skateboards.

But Mr Kiernan's unusual find has to take the cake.

"The current record is a bound and gagged garden gnome," he says. "There are gnome-haters out there, and we've got to hunt them down."