Pulau Semakau : where garbage creates its own ecosystem

Singapore is a small island, with millions of people contributing to thousands of tonnes of rubbish a day. Even with recycling efforts, that’s a lot of rubbish. Singapore has taken a novel approach and turned one of its offshore islands into a dedicated landfill site – one that is also home to various flora and fauna despite its key role as a giant waste receptacle. By Sheila Berman.

Singapore, 10 February 2018. At 719.1 sq km, Singapore could fit easily into Australia’s New South Wales, and still have wriggle room. With a population of around 5.7million, the city state’s size means that space is a premium. Residential and commercial developments are priorities, while the government is keen to ensure open spaces, parks and other greeneries are also available. But there is a catch – all those people produce a lot of waste that has to go somewhere.

 Pulau Semakau from the air. Image courtesy NEA.

Pulau Semakau from the air. Image courtesy NEA.

Island of Waste

According to Singapore’s National Environment Agency (NEA) website, “Singapore's growing population and booming economy have contributed to a about seven-fold increase in the amount of solid waste disposed.” This has risen from 1,260 tonnes a day in 1970 to a peak of just under 8,600 tonnes a day in 2016.

Recycling is encouraged but not everyone does it. In general rubbish streams, items that cannot be sorted or recycled are sent either to one of four waste-to-energy plants at Tuas, Senoko, Tuas South and Keppel Seghers Tuas, or to Pulau Semakau landfill.

The Semakau landfill is located on the eastern side of Pulau Semakau (Bahasa for Semakau Island) about four kilometres to the south of Singapore. It was originally the home of subsistence fishermen living in stilt huts, but was taken over by the Singapore government in 1987 with the object of turning it into a reclaimed waste depot. This made it the world's first offshore landfill, and it is now Singapore's only landfill.

 Six massive barges transfer thousands of tonnes of waste to Semakau every day. Image courtesy NEA.

Six massive barges transfer thousands of tonnes of waste to Semakau every day. Image courtesy NEA.

Phase 1 construction of Semakau Landfill commenced in 1995, and was built at the same time as the Tuas Marine Transfer Station (TMTS); where the waste would be loaded onto barges for shipping to Semakau. The first phase was completed in 1999, at a total cost of S$610 million. Phase 2 expansion began in Jan 2014 and was completed mid-2015 at a total cost of S$36 million.

The final works saw a 7km-long perimeter rock bund (wall) completed to enclose a part of the sea between Pulau Semakau and Pulau Sakeng. This allowed a massive 3.5 square km contained area to be created, with a projected total capacity of more than 60 million cubic metres. Rubbish began to arrive at Pulau Semakau in April 1999, and at current estimates the island will continue to swallow Singapore’s rubbish until it is full up in 2045.

Trip to the Tip

Although a working industrial waste site, the island is open to visitors who register and request a trip three weeks in advance using the NEA website. Due to operational work, visits can only be made on weekends - and are subject to the approval of the NEA. Visitors are required to hire a ferry at S$400 return, or join an organised tour to minimise cost.

Guests to the island are treated to an educational briefing on solid waste management in the facility, as well as a tour of the landfill facilities. Lucky visitors also have the chance to take a three-hour intertidal walk during low tide. This allows them to take in a surprising collection of mangroves, seagrass, coral reefs, crabs, starfishes, sponges, shrimps and other interesting – and unlikely for a rubbish dump –flora and fauna. Keen twitchers can also tick off spottings from a list of some 66 species of birds that have made the island their home.

Surprisingly tidy

Visitors remark on the tidiness of the facility, and the island as whole. “Semakau is a very tidy place, well managed within the technology available there,” said one, Australian author Russell Darnley. “There was no waste material left lying around at all,” he said after a visit to the island.

In fact, Singapore is keen to underline its eco-credentials. It is billed as “a unique landfill coexisting with vibrant marine eco-system, grassland and shoreline habitats.” To make sure the quality standards are baked into the whole system, the Waste Disposal Process (WDP) begins even before the barges arrive to the island. The NEA describes how the waste – ash and other non-incinerable waste from the TMTS – is loaded into one of six barges, each holding 3,500 cubic metre of waste, then transported to the Semakau landfill using three pusher tugs. The mix of waste is roughly 65% ash, and 35% non-incinerable landfill.

 The barges are unloaded into trucks which take the waste to storage cells. Image courtesy NEA.

The barges are unloaded into trucks which take the waste to storage cells. Image courtesy NEA.

Large excavators with specially designed grabs unload the solid waste from the barge, and drop it into 35-tonne off-road dump trucks, which use a 10m-wide paved roadway along the top of the perimeter bund to access to all sections of the landfill. The dump trucks then travel to a designated tipping site and unload both incinerated ash and non-incinerable waste into a specified landfill cell. Bulldozers and compactors then level and compact the waste. Once full, each cell is covered with a layer of earth. Eventually, grass and trees will take root to form a green landscape.

One advantage of the system used at Semakau is that as much of the waste is delivered in the form of incinerated ash, the problem of methane generation from decaying organic matter has largely been eliminated.  “This is not to say that the ash is completely inert,” noted one observer. “Singapore experiences high rainfall and the landfill pits could theoretically overflow. This means it is necessary to have a leachate treatment plant on Semakau to avoid contamination of surrounding water ways.”

To mitigate this, the landfill pits are all lined with an impermeable membrane, a tough plastic, and a layer of marine clay. This helps ensure the ash and rainwater that accumulates in the landfill is contained – but the membrane could have a limited life span and eventually allow leaching into surrounding areas. “I worry about the long-term consequences,” added Darnley.

 Semakau has Singapore's largest wind turbine providing renewable power. Image courtesy NTU.

Semakau has Singapore's largest wind turbine providing renewable power. Image courtesy NTU.

However, Singapore’s NEA is keen to point out that the Semakau project also opens up possibilities for positive sustainability and research. Pulau Semakau and the neighbouring area is already home to the largest barramundi farm in Singapore, run by Kühlbarra; the location was chosen for its strong current and high oxygen content, necessary for healthy fish growth.

The NEA has also investigated the possibility of turning some 90 hectares of the island into a self-sustaining eco-park. If the project comes to full fruition, it would see test-bedding of renewable and clean technologies such as wind, solar, tidal power, fuel cells, desalination, renewable clean fuel and more. As a first step, in 2017, Singapore’s largest wind turbine was set up on the island, along with a linked solar generation plant to provide much of the island’s power needs. Not bad for a rubbish tip!