Plastiki, the boat made from 12,500 plastic bottles, will leave New Caledonia this week for the final leg of its journey to Sydney.

The 60-foot catamaran has sailed nearly 7,000 miles since leaving San Francisco 108 days ago to raise awareness of the Great Pacific Garbage Patch, the vast, floating, rubbish patch in the world’s largest ocean.

Inspired by the 1947 trans-Pacific Kon-Tiki expedition from South America to Polynesia by Norwegian explorer Thor Heyerdahl on a raft made from carved-out balsa husks, British adventurer, ecologist and banking heir David de Rothschild, 31, concocted the idea after reading a UN report on ocean ecosystems.

Plastiki, in which the bottles provide 68 per cent of the buoyancy, has already stopped in the Line Islands and Western Samoa.

The voyage, which aims to highlight the dangers of plastic pollution, over-fishing and climate change to the world’s oceans, is expected to start its last and most challenging leg tomorrow after arriving in Noumea, New Caledonia, last week.

Mr de Rothschild said: ‘The variables are outside of our control which make it very frustrating.

‘There’s a weather window to get across (the lagoon surrounding New Caledonia) that we basically have to try and jump in.’

Strong headwinds will force Plastiki to be towed into Sydney, as the vessel cannot sail upwind, so it will head for Coffs Harbour, 340 miles up the New South Wales coast.

‘It’s very humbling to have been able to live on the ocean for such a long period of time,’ Mr de Rothschild said.

‘(You) start to really dig deeper and see the subtleties in the ocean – the different colours and the characteristics and the shades and be out there and let it seep in to your very being.

‘It makes you realise the enormity of the challenge.

‘It’s the end of the voyage and it’s at that point when everyone is just excited to complete this leg of the journey, (but) I think for me it’s just one leg and one chapter in this story that is the Plastiki.

The Plastiki’s bottles are packed together in a ‘pomegranate-like’ structure and fixed to pontoons and it uses fully renewable energy sources including solar, wind and sea turbines.

It is held together with a fully recyclable plastic called Seretex and an organic glue made from cashew nut husks and sugarcane, while its sails are also made from recycled plastic.

While in Sydney, the boat will be moored at the Australian National Maritime Museum at Darling Harbour.