Wednesday, June 8, 2016

A rare glimpse into the processes behind Singapore's waste disposal


By Monica Kotwani

08 Jun 2016

SINGAPORE: Last year, Singapore generated 7.67 million tonnes of waste, an increase of almost 160,000 tonnes compared to 2014. The amount is increasing with population growth and rising affluence.

In the 1960s and 1970s, landfills existed on the mainland, in places like Choa Chu Kang and Lorong Halus. Over time, the process has become more advanced, but also remote. Much of it takes place out of plain sight of the people who produce the vast amounts of waste.

On Wednesday (Jun 8) the National Environment Agency (NEA) offered a rare glimpse of what happens after rubbish is tossed down chutes, when it arrives at Tuas South Incineration Plant, and finally, at the Semakau Landfill.
At Singapore's largest incineration plant, the first stop for the truckloads of rubbish is at the refuse reception hall. The area is vast, with wide berths for each truck. These are connected to a discharge chute - a 32m-deep, cave-like structure that holds an incredible amount of waste - from washing detergent bottles and mountains of plastic bags, to rubber boots and paper. Many are items that could have been recycled instead of ending up here.

A few floors up, a staff member sits in front of a glass window overlooking the waste storage area. He controls two overhead grab cranes that collect a mound of rubbish each time, only to drop them back down. This happens three times.

The process is to "mix in" the different types of waste- plastic, paper and food. This is done as materials burn at different temperatures. A consistent mix of materials is needed in each batch for the furnace to operate efficiently.

The final grab, weighing about eight tonnes, is chucked into the mouth of the incinerator. Waste in the furnace burns at between 850 and 1,000 degrees Celsius. Emissions and pollutants from the burning process are treated before being released through the chimneys. And the heat produced during combustion is converted into electricity, 80 per cent of which is sold.

The entire process from start to finish is monitored at the plant’s nerve centre.

The incineration reduces the volume of waste by 90 per cent. Ferrous scrap metals are separated from the ash, and recycled.

The ash then takes a three-hour journey, by sea, to the Semakau Landfill, where excavators are on hand to transfer it from the barges in which it arrived, and onto dump trucks. The ash is then tipped into a cell - a sea space that has been enclosed within the landfill's bund, built with impermeable membranes to ensure the ash does not leak into the sea.

Since July 2015, the National Environment Agency has started to fill the cell that was built as part of the landfill’s Phase II development. It is expected to meet Singapore’s waste disposal needs until 2035.

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