Waste-to-energy Incineration Fly Ash Reborn As Semakau Landfill Island
Singapore is a bustling city state at the southern tip of peninsular Malaysia. Independent from Malaysia since 1965, it has a dense population of 4.7 million people crammed into 269 sq. miles (697 sq. km)— that’s roughly 3.5x the size of Washington D.C.
In spite of its lacking land mass, the tiny country is a major economic hub in Southeast Asia and boasts one of the best standards of living of any Asian city, and even rivals many metropolis overseas.
It’s a city that is well planned, tightly regulated, visually attractive, and thankfully lacking the woeful pollution that afflict other centers like Hong Kong and Shanghai.
Waste and the City
All the economic activity and large population of course is not without its downside: waste. In 2008 the total volume of solid waste had reached 5.97 million tons. Luckily, according to government figures, roughly 2.24 million tons (approx. 56%) of this was recycled. That still left a lot left to deal with.
For Singapore, most of this excess is processed by waste-to-energy (W2E) incineration. The country has 3 operational incinerators in different locations around the country. According to the National Environment Agency (NEA), annually these plants contribute to 3% of the nation’s electricity production. The WTE plants are designed and equipped with advanced flue gas treatment systems so that emissions comply with local emissions regulations. Dust, particles, and other pollution from incineration are managed by bag filters, gas scrubbers, and electrostatic precipitators installed at the plants. Dioxin is controlled within legal limits.
Under the Sustainable Development Blueprint, Singapore has set itself the target of increasing the recycling rate to 70% by 2030 and striving towards zero landfilling.
In 2008, the 4 WTE plants incinerated some 2.45 million tonnes of waste and generated some 1.05 million MWh of electricity. Net avoided greenhouse gas emissions from methane releases at landfills and fossil fuel use at power plants for electricity production amounted to 3,450 kt CO2 equivalent.
While burning the waste reduces the volume considerably, in a country with little land to spare, one big issue remained: where to safely put all that leftover fly ash?
Filling the Gap
Luckily, Singaporeans are incredibly efficient and clever. In the early 1990s, the government came up with the plan to construct a landfill island between two atolls 5 miles (8 km) off the southern coast of the country. The grand vision: put all that fill to good use, use existing atolls to construct a new island, regenerate mangrove and aquatic ecology, and use as a center for education, recreation, and research.
Well, construction kicked off in 1995, filling operations commenced in 1999, and Semakau Landfill became open for public recreation in 2005. The total cost of construction to get the new island established was SG$610 million.
The island is quite an engineering feat. The land area is 865 square acres (350 ha2) and a total disposal volume of 2.2 billion ft3 (63 million m3). This area is divided into two phases. Phase I has 11 fill cells while Phase II has yet to be divided into smaller segments. Each day, the cells receive 2000 tons of ash and other landfill matter, mainly construction waste. Other hazardous, toxic, and electronic waste is handled elsewhere in safe fashion.
It is predicted that Phase I will handle Singapore’s waste disposal needs until at least 2045, after which Phase II may become operational. The cells are each lined with sand, concrete, and an impermeable geomembrane to prevent any leachate from entering the water. Each cell also has a monitoring station to keep an eye on any potential environmental effects.
Connecting People with Ecology
So far, it’s been pretty smooth sailing. The thriving marine life including coral reefs, mangroves and mudflats are home to everything from starfish to rare insects. More than 80 species of birds, including endangered shorebirds such as Great-billed Heron and Malaysian Plover have made the island their home. Other residents include 33 species of butterfly and 75 species of plants.
Such an abundance of wildlife just off the coast of a major city attracts quite a bit of interest. Four groups have access to the island: Star gazing is made possible through the Astronomical Society of Singapore , the Raffles Museum of Biodiversity Research hosts intertidal walks, Nature Society of Singapore brings bird watchers, and Sport Fishing Association periodically brings fishermen to the island.
Educational groups also visit the throughout the year from schools and community organisations. This has enabled waste to become visible to Singaporeans so they understand it has to be dealt with somehow. Such visibility has helped inform reduction measures and recycling initiatives undertaken by the NEA as part of their key goals of zero waste to landfill.
Other Waste Management Possibilities?
While Semakau is an elegant solution to a complex problem, there are other possibilities for the future. In terms of handling the ash from incinerators, the NEA is currently trialing it as a building material in several roads. If successful, there’s the possibility it could be used in other construction projects in the future.
Taking a step back up the waste stream, as a lot of the refuse is domestic food waste, it might be feasible to set up some kind of local composting program using an industrial scale, vertical compost unit . These have been used elsewhere in the world to great success, can handle large volumes of wet household waste, and produce a dry substance that easily biodegrades and adds to soil fertility. With major agriculture operations taking place in neighboring Indonesia and Malaysia, there could be a whole new export product in the making.
The NEA is also serious about upping the recycling rate and has a 60% target for 2012. Depending where you are in Singapore, recycling coverage can be patchy and ranges from sparsely located bins for entire building complexes, to doorstep bag service. Continuing public education will be key to making this successful, as well as a comprehensive program with visible, easy to use bins.
And what about consumer behavior? The NEA has an accord with many consumer brands and retail outlets around reducing packaging. While noble in intention, one has to wonder if, in the face of increased consumer activity, this will result in any serious waste reductions. Getting people to buy less “stuff” is pivotal, and in Singapore shopping is the national sport. Changing the mindset could prove difficult, if not impossible. One can only hope that as awareness around Semakau Landfill continues to grow, and more people visit the island to learn about the waste management of Singapore, sentiment will change with time.
Check Out Semakau
Next time you pass through Southeast Asia, be sure to try and check out the inspiring Semakau Landfill island.
For more information on Semakau Landfill, check out the book Habitats in Harmony. Special thanks to Jeremiah Koo and Mary Chin.
By Chris Tobias, appearing courtesy of Celsias.
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