Semakau 11.11

Journey of trash

Semakau landfill

The waste we produce each day comprises recyclable waste, which should go into the blue recycling bins, and non-recyclable waste that is discarded.

The waste is collected by waste collectors and transported to one of Singapore’s four Waste-to-Energy (WTE) plants.

The refuse trucks tip the waste into a bunker, where cranes then feed it into incinerators. The process cuts the waste volume by up to 90 per cent. The heat produced is harnessed to produce electricity, which is fed into the national grid.

Ferrous and non-ferrous metals – such as aluminium and copper – as small as 2mm are recovered from incineration bottom ash at the metal recovery facility, using magnetic and eddy current separators.

The remaining ash and non-incinerable waste is transported to Tuas Marine Transfer Station.

New HDB estates use Pneumatic Waste Conveyance System – an automated waste collection with vacuum-type underground pipe network to move household waste to a sealed container.

In 1989, the Central Refuse Chute system was launched, where HDB flats had a common hopper at the lift landing of each floor instead of a hopper in every kitchen. This allowed for more efficient refuse collection.

Each day, about 600 refuse trucks roll into Tuas South Incineration Plant, Singapore’s fourth and largest waste-to-energy (WTE) plant. The first WTE plant was built in 1979 at Ulu Pandan, at a cost of $130 million.

At the current waste disposal rates, a new offshore landfill will have to be identified every 30-35 years. By 2035, the ash generated from incineration may have nowhere to go as Semakau Landfill is projected to run out of space by then.

In 2018, Singapore generated 7.7 million tonnes of solid waste of which 3% ended up on Semakau Landfill. It cost a total of $646 million to construct the landfill, which is located 8km south of Singapore mainland.

Pulau Semakau and its neighbouring area are home to the largest barramundi farm in Singapore. If you’d like to visit Semakau Landfill and WTE plants, go to shorturl.at/uvHOW

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A tugboat nudges a barge, which takes the waste on a 33km journey to the Transfer Building at Semakau Landfill.

Large excavators are used to unload the waste from the barges onto 35-tonne dump trucks.

The dump trucks take the ash to the Floating Platform, where it is discharged into the giant Phase II cell.

The fish farm has its fish nursery located on the island. The farm is ramping up its fish production threefold, to almost 1.8 million fish fry per year.

The National Environment Agency planted 400,000 mangrove saplings on 136,000 sq m of man-made mudflats. The mangroves act as biological indicators, giving early warnings if toxins leak into the sea. The mangroves have been thriving in the waters off Semakau Landfill since 1999.

Just off the landfill is a local floating fish farm, which rears barramundi in waters chosen for its strong current and high oxygen content.

Under Phase II of the landfill’s development, a gap on the southern tip was closed, forming a single giant cell. This new design saves cost and created more space for landfilling. Completed in 2015, it increased the landfill’s capacity by 14.5 million cubic metres (the equivalent of nearly 5,800 Olympic-size swimming pools).

The Floating Wastewater Treatment Plant treats excess water in the cell before releasing it into the open sea. This prevents flooding and pollution to the surrounding waters.

The perimeter rock bund (the wall encasing the landfill) is lined with an impermeable membrane and a layer of marine clay. This ensures that nothing seeps out from the landfill cells into the sea.

Here, incineration ash is deposited into the Phase II cell from the Floating Platform, which can be shifted wherever it is needed.

There are more than 9,500 sq m of solar panels and a wind turbine on the landfill, with a total output of 1.5 megawatts, enough to power up to 350 four-room Housing Board units for a year when operational. They are part of the Renewable Energy Integration Demonstrator-Singapore (REIDS) project by Nanyang Technological University.

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The heat from the combustion generates steam which drives turbogenerators to produce electricity. The incinerator operates between 850 and 1,000 deg C, reducing waste to ash which is about 10% of its original volume.

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