There's a very hungry creature on the pristine Lady Elliot Island, which sits on the southern tip of the Great Barrier Reef off Queensland's Fraser Coast.

No, it's not the reef sharks, sea turtles, manta rays or array of other colourful characters that make snorkelling and diving off this postcard-sized gem such a joy.

It's a huge food scrap-eating giant known as OSCA, who turns kitchen waste and cardboard into life-giving compost.

While my husband, 16-year-old son and I snorkel around the island's western reef — delighting at parrot fish, clams, coral, and an abundance of other iridescent marine life — the composter is chewing through the remains of our buffet breakfast on the first stage of its journey into nutrient-rich compost.

Lady Elliot Island is home to a state of the art Hybrid Solar Power Station to supply energy. ( ABC News: Cate Carrigan )

The final product will go to revegetating the coral cay that had a metre of topsoil ripped up as part of guano (bird poo) mining operations in the 1860s.

When the miners left, the island was denuded — just a herd of imported goats remained as emergency provisions for shipwrecked sailors.

OSCA, an acronym for On-site Composting Aparatus, is part of an ecologically-sustainable model developed to protect and restore this tiny cay, while hosting international and domestic tourists keen to get up close and personal with the island.

There's also a desalination plant to ensure the resort has enough water, and a state of the art Hybrid Solar Power Station, inverters and a generator to supply energy for cooking, refrigeration, cooling, lighting and for the island's wastewater treatment plant.

An aerial view of Lady Elliot Island on the Fraser Coast. ( Supplied: Lady Elliot Island Eco Resort )

'We never really imagined we could own it'

This eco-resort island is the passion of former motorbike racer Peter Gash, the managing director, custodian and steward, who's held the lease since 2005.

Peter, who first visited the island in 1980 as a 21-year-old motorbike racer, was struck by the impact of mining on the island compared to the nearby, unmined, Lady Musgrave.

Imported goats were the only thing that remained on Lady Elliot Island after mining operations finished. ( Supplied: Lady Elliot Island Eco Resort )

He and his then-girlfriend, now wife Julie decided they wanted to live in the area.

"We just talked about it and wondered how we could ever have an involvement with this incredible part of the world," he said.

"We never really imagined we could own it — maybe just take people there, run a business and make a difference."

Peter gave up motorbike racing and obtained a pilot's licence, and together, the couple started working two jobs a day, saving as much as they could.

Peter started flying seaplanes of tourists to and from Lady Musgrave and eventually nabbed an opportunity to buy the air service — going into serious debt, while hoping it would pay off in the long run.

Peter first visited the area in the 1980s, when it was without vegetation. ( Supplied: Lady Elliot Island Eco Resort )

When the opportunity arose to bid for the lease on Lady Elliot Island from the Commonwealth Government, he was ready.

He had visited often and talked to the then lease-holder Don Adams, a keen aviator who started the eco-resort in the 1960s.

From the get-go, Peter began a revegetation plan, planting more and more trees, breaking off the limbs and sticking them straight into the coral ground, which had been deprived of nutrients and topsoil by guano mining over 100 years ago.

"I was like Johnny Appleseed wandering around planting wherever I could," Peter said.

"I had no money so we were up against the wall and it wasn't very successful because we were just putting it into hard coral."

From the get-go, Peter and Julie began a revegetation plan. ( ABC News: Cate Carrigan )

'The more I give to the island, the more it gives to me'

The pair sought advice from a National Parks agronomist on using introduced species to bring back nutrients, before transitioning to purely indigenous species.

With the help of friends, who dedicated hours of volunteer labour, their hard work started to pay off.

Now, thousands of trees have been planted and thousands more are being grown in the island nursery.

"What's amazing is that the more I give the island and nature, the more it gives me," Peter said.

"For me personally, it's just a great feeling that things are getting better. But it also means that more guests are coming out and they spend money and we can then put that money back into the island."

While Peter always believed the revegetation would be good for the island and the many birds that come to roost and nest, he has since discovered it's also good for the coral.

"Birds come back to the trees, their poo falls to the ground, mixes with the vegetation and soaks down into the sub-strata which is quite a porous," he said.

"We have now started to learn that the sea water comes in and meets the freshwater which is rich in nutrients — nitrogen and phosphorous — and this is then taken out in very fine concentrations.

Peter said the island now has "better coral than anyone could have imagined". ( Supplied: Lady Elliot Island Eco Resort/Colin Baker )

"Scientists have always thought nutrients are bad for coral, but we're finding that in these very fine concentrations, it is very good for corals."

Peter said the island now has "better coral than anyone could have imagined".

'If a little Aussie digger like me can do it, so can others'

The couple also sought to ensure energy use on the island was more sustainable.

They made the desalination plant more efficient, transitioning away from greenhouse-gas emitting diesel fuel and noisy generators.

Peter Gash (left) and his wife Julie (right) have held the lease to Lady Elliot Island since 2005. ( Supplied: Lady Elliot Island Eco Resort )

"I wanted to move to solar but the desalination plant was guzzling up 30 to 40 per cent of the island's power and only producing 12 to 14 litres of water a minute, so we had to make it more efficient," Peter said.

"We're now producing 45 litres per minute and we're doing that in five or six hours a day — the solar window — using our Hybrid Solar Power System."

Following the arrival of another 80 solar panels and 48 batteries last month, Peter hopes Lady Elliot will be totally self-sufficient by Christmas.

But, if that goal isn't reached, there's a commitment to reach it no later than December 2020.

Meanwhile, OSCA — the $110,000 composter — has been put through his paces.

While brought in to replace the inefficient (and smelly) system of burying the food waste in a pit, the machine wasn't generating the heat necessary to break down matter into a ready-to-use compost.

The OSCA composting system is helping revegetate Lady Elliot Island. ( Supplied: Lady Elliot Island Eco Resort )

So, using his usual find-a-solution approach, Peter and his team developed a windrow aerating system, where the post-OSCA material is placed.

It is churned once a week for three months, then mixed with woodchips and turned into beautiful black soil, to be used for revegetation and on the runway.

While he may have had some regurgitation problems, OSCA has proved his worth, impressing a visiting team from the Great Barrier Reef Fund, who got the Commonwealth and Queensland governments and corporate sponsors on board.

"We had been pouring in a lot of money — over a million dollars — and it was hard to get cash together to invest in the accommodation which needed attention," Peter said.

"Now we are getting a substantial amount of money, so [we] now can spend it on the buildings."

For Peter and Julie, Lady Elliot has never been about making a profit.

The couple draws a wage from their aviation business, with everything they make reinjected back into the island, either into tourist infrastructure, such as boats and accommodation, or into the revegetation program.

"It's giving back to us. My business is booming because people want to come to one of the best places on the reef. I gave to the island and it's giving back to me," Peter said.

"I just care for the future of the planet — not just for humans but for all the species. We humans are amazing creatures but we make mistakes.

International and domestic tourists are keen to get close and personal with the tiny cay. ( Supplied: Jeremy Somerville )

"So, for me, let's fix Lady Elliot Island and leave it better then when we found it. And if a little Aussie digger like me can do it, so can others.

"We can all make a difference and the planet is saveable. We're all in this together. We're all one family."