Integrated thinking: Solid waste management in Singapore

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The small island nation of Singapore - where waste production rose six-fold from 1970 to 2000 - has been facing the challenge of handling waste with limited space. Integrated planning and the goals towards zero waste and zero landfill are now turning the tide on waste.

Singapore is a highly urbanized and industrialized small island nation with a land area of 697 km2 and a population of 4.2 million. It has four waste-to-energy refuse incineration plants and an offshore sanitary landfill for the disposal of non-combustible waste.

Given that the rate of waste disposed by its citizens had risen six-fold between 1970 and 2000, it is no surprise that the nation has set an ambitious target to achieve zero landfill. Indeed, if this growth in waste were not curtailed, Singapore would need to build a new 3000-tonne/day incineration plant every five to seven years and a new 350-hectare landfill every 25 years to cope with the waste.

To address this potential problem, Singapore has set up an integrated solid waste management system in the past three decades that incorporates recycling, collection and disposal. Working hand in hand with key stakeholders in the private and government sectors as well as the general public, Singapore’s National Environment Agency (NEA) has formulated a range of strategies and programmes to achieve its objectives for curbing waste growth and supporting sustainable waste management.

Waste minimization

Starting at the top of the ‘waste hierarchy’, naturally a key objective is to reduce waste production. In this regard, the main portion of Singapore’s non-combustible waste comes from construction waste, stabilized industrial sludge and used copper slag from the marine industries, residues and ashes.

Over the years, much of these have been diverted for reprocessing. For instance, 94% of the construction and demolition waste was recycled in 2005. At the same time, the country has also adopted specific measures to minimize waste generation, such as the careful selection of design and construction methods that minimize waste production. For example, contractors who want to tender for large government projects are required to be ISO-14001 certified.

By undertaking these measures, Singapore is taking a big leap forward to achieving the ultimate goal of ‘Towards Zero Landfill’. And it is not resting on its achievements so far. The next step is to raise the bar by striving for zero waste. This means moving upstream to avoid waste at source and bringing the producers of waste on board to collaborate with the NEA and the community to reduce waste.


The Semakau offshore island landfill receives the non-recyclable, non-combustible parts of Singapore’s waste and is designed to be in harmony with the surrounding ecosystem Click here to enlarge image

For example, the NEA, the Singapore Environment Council, major supermarkets and the Singapore Retailers Association jointly launched the campaign ‘Why Waste Plastic Bags? Choose Reusable Bags’ in February 2006.

NEA has also initiated a voluntary packaging waste programme with the industry to reduce packaging waste in Singapore. The agreement is scheduled to be finalized and signed by mid 2007 and would last for five years.

Recycling

The second strategy the NEA adopted is to promote waste recycling in the industrial and commercial sectors as well as in households.

Recycling commercial and industrial waste

About half the waste disposed of in Singapore comes from the industrial and commercial sectors. These companies have to pay for the collection and disposal of their waste. This approach, coupled with encouragement by the National Environment Agency, has helped to motivate the industrial and commercial sectors to recycle wastes such as metals, construction and demolition waste, horticultural and wood waste, slag, plastic and some types of food waste. In 2005, 94% of construction and demolition waste, 92% of ferrous waste, 51% of horticultural waste and 7% of food waste were recycled.

To promote adoption of innovative environmental technologies, the NEA has set up a SG$20 million (€10 million) Innovation for Environmental Sustainability (IES) Fund. The IES Fund provides financial grants to assist Singapore-based companies to defray part of the cost for trialling innovative environmental technologies that could contribute to environmental sustainability. Recycling projects supported by the IES Fund include:

  • production of pre-cast concrete drainage channels using recycled aggregates
  • conversion of horticultural waste into packaging materials
  • processing of ladle furnace slag, a by-product of the steel-making process, into road construction material.

The recycling industry in Singapore comprises companies with the capability and capacity to recycle and process electronic waste, food waste, wood waste, horticultural waste, used copper slag, construction and demolition waste, ferrous waste and plastic waste.

Recycling in the community

In April 2001, the NEA launched the National Recycling Programme (NRP) to provide a convenient means for residents of public and private housing estates to recycle. Under the NRP, recycling bags or bins are distributed to each household for residents to store their recyclables. The recyclables are collected once every two weeks by the appointed recycling companies.


A marine transfer station receives non-combustible waste which is then loaded onto barges and shipped to the landfill Click here to enlarge image

The participation rate in the NRP was 15% at the start of the programme and reached 56% in 2005. To further enhance the NRP, the NEA is working with its partners to provide all housing estates with recycling bins placed at convenient locations. This will make it even more convenient for residents to recycle as they will be able to deposit their recyclables whenever they want, in addition to the collection every two weeks.

Public recycling bins

Furthermore, almost 6000 public recycling bins have been placed at locations with high human traffic. These include places outside several mass rapid transit (local train) stations, food centres, bus interchanges, airport terminals and pedestrian malls.

Recycling in schools

In September 2002, the Recycling Corner Programme for schools was launched with the aim of educating and inculcating good 3R (reduce, reuse and recycle) habits in young people. Recycling bins for paper, drink cans and plastic bottles are placed at Recycling Corners within school premises. Students take charge of the Recycling Corners and put up interesting information and displays about the 3Rs.

These activities help generate interest and build a sense of ownership among the students. By the end of 2006, 84% of schools had joined the Recycling Corner Programme.


The waste is unloaded from the barges onto dump trucks Click here to enlarge image

Highly enthusiastic students are also identified by the schools and trained as Environment Champions to promote recycling in their schools. They are responsible for conducting talks on the environment and assist in planning, organizing and running recycling/environmental activities.

3P partnership and public awareness

Changing mindsets and influencing behaviour take time. To do so, the NEA has been engaging grassroots organizations, non-governmental organizations and educational institutions in holding environment-related events and encouraging them to lead in reaching out to the rest of the community. This is referred to as the 3P sectors partnership - referring to the people (general public), private (non-government) and public (government) sectors.

The educational and awareness programmes on the 3Rs have to be sustained and targeted to the community, schools and the work force. One such awareness campaign is the annual Recycling Day. The aim of the campaign is to keep reminding the public - schools, community, non-governmental organizations and recycling companies - of the importance of recycling.

At the opening ceremony of Recycling Day 2006, the Minister for the Environment and Water Resources, Dr Yaacob Ibrahim, launched a new scheme to recover and recycle used drinks cartons. The scheme was a collaborative project with Tetra Pak Singapore and the recycling companies.

Volume reduction through incineration

Given the land scarcity constraint, it is not surprising that Singapore has adopted waste-to-energy as a disposal method. Incineration reduces waste volume by 90% and only the ash remaining after incineration and the non-combustible waste, which constitutes 10% of waste disposed, is sent to Singapore’s only landfill - Semakau landfill.

The incineration plants are fitted with advanced pollution control equipment comprising electrostatic precipitators, lime injectors and fabric filters to treat and clean the flue gas from the combustion process. Heat from combustion is used to generate steam in boilers which drives turbines to produce electricity. In 2005, the four plants generated a combined total of 938,284 MWh of electricity. Scrap iron is also recovered and recycled at a local steel mill.


Semakau landfill welcomes visitors to see its ecosystem LEFT TO RIGHT Mangroves replanted since landfill construction • Intertidal sea life such as starfish and anemone Click here to enlarge image

Although incineration offers the advantage of high waste volume reduction and helps to conserve landfill space, it is by itself not adequate if more waste is generated each year. This would then put additional demand to build more incineration plants and landfills.

Semakau landfill

The SG$610 million (€305 million) offshore Semakau Landfill extends over an area of 350 hectares and has a fill capacity of 63 million m3. To create the offshore landfill space, a 7 km perimeter bund (embankment) was built to enclose part of the eastern sea area off the island, Pulau Semakau, as well as another small island, Pulau Sakeng. The entire perimeter bund is then lined with an impermeable membrane. Any leachate generated within the site is treated in a dedicated leachate treatment plant to national discharge standards and the effluent is discharged into the sea.

A corresponding marine transfer station, which sits on a seven-hectare site on the western end of the main island of Singapore, receives waste which is dumped into barges. The waste comprises the non-combustible components of Singapore’s waste, such as construction and demolition waste, stabilized industrial sludge, and copper slag, as well as ash from the refuse incinerators. The barges then make a 25 km sea journey to the landfill, where the waste is unloaded onto dump trucks for the final journey to the operating cells. Bulldozers and compactors are deployed to spread out and compact the waste.

A unique aspect of Semakau landfill is that throughout its planning, design and construction, and since the start of its operation, painstaking efforts have been made to protect the island’s ecosystem and preserve its rich natural environment and biodiversity. In July 2005, the landfill was opened for recreational activities organized by three special interest groups - the Sport Fishing Association of Singapore, the Nature Society of Singapore, and the Raffles Museum of Biodiversity Research (RMBR). The Semakau landfill has since received more than 1300 visitors.

The visits came after extensive surveys lasting more than a year by the RMBR to map out the inter-tidal community present in the western coast of the island of Pulau Semakau, which was protected by special screens at the eastern part of the island during construction to avoid adverse impact on marine life.

Experts were also engaged to ensure that the replanted mangroves in two plots totalling 13.6 hectares grew well. Today, these mangroves, which were planted to replace those uprooted during construction, are thriving. While there is a network of monitoring wells along the perimeter bund of the landfill, the mangroves can help act as second-line indicators of pollution should there be a leak in the impermeable membrane.

Conclusion

By adopting its waste strategies, Singapore has seen an increase in recycling rate from 40% in 2000 to 49% in 2005. Waste growth has also been curtailed. The total waste (domestic and non-domestic) disposed of in 2005 was 7000 tonnes per day, an 8% reduction compared to 2000. As a result, the lifespan of Semakau landfill has increased from 30 years to about 40 years, while the need for additional incineration plants has been reduced from one in every 5-7 years to one in every 7-10 years.

By reducing waste disposal at the incineration plants and landfill, Singapore is striving towards achieving its long-term goals of ‘Towards Zero Landfill’ and ‘Towards Zero Waste’.

Vincent Teo is Chief Engineer (Waste Minimization), National Environment Agency, Singapore. e-mail: vincent_teo@nea.gov.sg

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