Landfill is a site for the disposal of waste materials by burial and is the oldest form of waste handling. According to USEPA 2006 landfills are world’s third largest anthropogenic emission source, accounting for about 12 % of global methane emissions.
Apart from emissions; long lifecycle of the landfill sites and inappropriate disposal of waste on open dumping grounds have increased air pollution, contamination of the ground water and resulted in underground water/ river pollution in nearby areas. Therefore the question arises weather land filling is solution to waste or source of pollution?
The Singapore government has provided sustainable answer for above question by developing world’s first offshore Semakau landfill.
Semakau landfill is the world’s 1st man-made offshore landfill was opened in 1999 at the cost of SGD$610 million and is currently Singapore’s only landfill. It was created by the amalgamation of Pulau sakeng and anchored to Pulau semakau.
Usually landfill is considered as source of festering mounds of pungent garbage but semakau landfill is home for more than 700 types of plants, animals and several endangered species. It has been transformed in to an eco-park, mangroves and coral reef rings the island and many nature-related recreational activities are conducted on landfill. Therefore instead of stinky landfill it has gained title of being ‘nature heaven.’
Fig 1: Semakau offshore landfill
How did they do it?
To avoid risk of soil pollution Singaporean government located offsite landfill 8 miles south of Singapore. To avoid water pollution and develop a sustainable landfill following steps were carried out:
- They built a barrier between the landfill and reservoir. This barrier was created by constructing significant underground wall of bentonite, soil and cement.
- They established a network of wells and pumps to collect the leachate due to rain and channeled it in to system of tanks and lagoons for treatment.
- For filtration of contaminants bioremediation techniques were implemented.
In order to make process more efficient they first pre-treated leachate into tanks and lagoons where suspended solid particles were removed and oxidation was conducted to remove organic matter and break down of Nitrogen compound.
- The leachate is then channelized into five reed beds with three types of plant which can thrive in Singapore’s tropical climate as well as composition of extracted leachate. These plant species include cattails, vetivers and papyrus.
- The treated leachate is then channeled again into polishing pond for final filtration by water lilies before being channeled into sewers for conventional water treatments.
Fig 2: layout of Semakau offshore landfill
To develop this landfill Singapore switched to incinerating all of their waste and progressively filled landfill with layer of soil and plant vegetation and also surrounded the entire combined island by polymeric geo-membrane. Hence we can say entire landfill was laminated to prevent any entry of waste or pollutant in surrounding.
Why does India need offshore landfill?
Indian waste is increasing along with its population and GDP. It is estimated that the amount of waste generated in India will increase at a rate of approximately 1-1.33% annually. There are 53 cities in India which together generate 86,000 TPD of MSW at per capita waste generation rate of 500 g/day. Day by day waste generation and its management is becoming difficult task as finding new landfills in and around cities is nearly impossible because of poor track record of dumpsite operations and its maintenance in India and ‘not in my backyard phenomenon’. Hence instead of dumping waste in conventional landfill India can focus on developing offshore landfills.
Fig 3: current scenario of Indian landfills
Challenges of offshore land filling
- Offshore landfill requires large amount of land and every year about 200,000 tonnes of solid waste and ash are received at this landfill; considering this rate it is projected to run out of space by 2035.
- Incineration is main technique applied for waste disposal but it results in production of dioxin which is known to increase rates of cancer growth and other health problem.
Advantages of offshore land filling:
- Incineration is a popular and unquestioned method for landfill development as it is cost effective and reduce the volume of waste by 90%
- It also contribute in power generation
- At the initial stages of landfill development site clearance may be required but it shall contribute in more plantation as project proceeds for example Semakau landfill Singapore replanted more number of mangroves than they removed for site clearance.
Though project has few drawbacks and challenges but those can be encountered by reducing and recycling waste, developing more efficient segregation technologies and establishing cleaner techniques for remediation and filtration of pollutants.
Considering India’s population density; offshore landfill development would help to manage generated waste as well as it may provide additional land and employment opportunity in country.
Above scenario of waste disposal management through landfill is defiantly better than below current scenario of conventional landfills.