Studies urge sanitary land filling for Colombo and composting for smaller towns

By P.K. Balachandran

A look at two recent reports on garbage disposal in Sri Lanka indicates that sanitary land filling is the best option for disposing large volumes as in the Colombo metropolitan area, and composting is ideal for smaller volumes generated in the outlying areas of the country.

A 2015 study of garbage disposal in Colombo by EML Consultants Ltd. for the Central Environment Authority (CEA) had concluded that sanitary land filling would be the only practical way of disposing Municipal Solid Waste (MSW) in Colombo. 

But a 2016 paper entitled ‘Management of Municipal Solid Waste in Sri Lanka: A Comparative Appraisal of the Economics of Composting’ by Dr. T. Lalithasiri Gunaruwan and W. Neluka Gunasekara found that composting is the best method for the Pradeshiya Sabhas to adopt.

The EML Consultants’ study done at the instance of former Urban Development Secretary Gotabaya Rajapaksa recommended that sanitary land filling should take place at Aruakkalu in Puttalam District, 170 km from Colombo.

It said that the garbage, collected and stored at Meethotamulla in the outskirts of Colombo, should be transported to Aruakkalu by rail on a daily basis. At Aruakkalu it was to be dumped in a disused limestone mine which has a capacity of 4,700,000 cubic meters. The garbage was to be sanitised. 

The bottom of the landfill would be formed by laying down gravel or crushed stone for 30 cm and a 1,000g/m2 non-woven fabric. Further, a bentonite mixture of 30 cm and 1.5 mm and an HDPE sheet would cover the top of the non-woven fabric. The top of the HDPE sheet would be covered with 1,500 g/m2 of non-woven fabric. Leachate collection and treatment systems were incorporated in the design. 

The Aruakkalu site was found to be geologically safe as it was already a mine. Hydrological data showed that there was no danger of ground water pollution. Dirty water could be recycled and diverted to the fields around to support wild life. The recommendations were approved by the cabinet. 

Composting garbage

Rajapaksa ruled out conversion of municipal solid waste into compost on a large scale as this was not practical when the daily addition to the garbage mound was of the order of 1000 mt.

“Compost making is alright if the daily collection of garbage is about 25 tons or so, and not in the case of very large volumes,” Rajapaksa said. 

He dismissed talk of electricity generation from garbage as “nonsensical” and said that incineration is too expensive. 

“Sanitised land filling is the most practical in Sri Lanka’s case. In my travels abroad as Secretary Defence and Urban Development, I had enquired about garbage disposal methods and I was convinced that given the conditions prevailing in Sri Lanka, sanitised land filling is the best,” Rajapaksa said. 

In their paper in the NSBM Journal of Management published in the January-June 2016 issue, Dr. Lalithasiri Gunaruwan and W. Neluka Gunasekara have argued that composting is economically viable and can even be commercially profitable and nationally beneficial if it is properly managed. 

However, they do admit that in a case of the huge volumes as in the Colombo metropolitan area, sanitary land filling will be the best method of disposal.

Gunaruwan and Gunasekara base their argument in favour of composting on the fact that 66% of the garbage is organic matter with moisture content as high as 70 to 80%. A little over 54% of the waste is short term degradable and 6% is long term degradable.

Interestingly, while each individual generates 0.62 kg of garbage every day, only a fraction of it is collected by the local authorities. According to a JAICA study done in 2007, the 311 local authorities in Sri Lanka collected a total of 2,838 mt of garbage per day. But this was only 23% of the total municipal solid waste generated every day. And shockingly, even in Colombo and its suburbs, only 30% of the waste was collected.

Open dumping

As for the disposal of the collected garbage, open dumping without treatment has been the norm. This has created a major health problem with the untreated garbage producing highly polluting leachate (water coming out of the garbage). In 2004, the National Water Supply and Drainage Board had concluded that the ground water near garbage dumping sites were unsuitable for consumption. 

The dumping sites also produced greenhouse gases like carbon dioxide and methane. Uncontrolled burning of waste produces toxic gases. Uncontrolled dumping, as in Attidiya and Muthurajawela, had created flooding in the wetlands around and threatened wildlife.

Gunaruwan and Gunasekara observe that even uncontrolled and untreated dumping of waste was costing the government a lot. The daily expenditure per ton is Rs. 2,000 in Colombo and Rs. 1,200 in the outskirts.

Discussing the merits and demerits of the various methods of garbage disposal, the researchers say that incineration is not suited, given the moisture content in the waste. Sanitary land filling is based on high technology to prevent leachate and gas emission while decomposition takes place. And this is expensive. 

Land filling also demands large amounts of land, and such land located in isolated places may not be easily found, especially in thickly populated provinces like the Western Province.

While land filling may be the best for a big city like Colombo, composting is ideal or the smaller towns and villages. Composting can be economically viable and even commercially exploitable, if modern methods of management are used. 

There are no large scale composting units in Sri Lanka, but 115 of the 331 local authorities have taken to composting through the Government’s “Pilisaru Project” sanctioned by the Central Environment Authority (CEA). 

“Weligama model” and “Pilasaru model”

In the study, there was the “Weligama model” and the “Pilasaru model” of composting. Both worked with a daily input of 18 tons of garbage. Of the two, the Pilasaru model was the more expensive with an initial investment was Rs.23 million while in the Weligama model it was only Rs.11 million. Given the lower cost, the Weligama model could be replicated. 

The Weligama model was able to produce 1.5 metric tons of compost per day from 18 tons of garbage. The unit was able to make Rs. 370,000 per month from the sale of compost at an average price of Rs. 8,500 per month. With better separation of the garbage, the Weligama model would be able to produce more compost.

To encourage compost production, the economists suggested that the Government mix compost with chemical fertiliser which will not only bring down the quantum of fertiliser import but also enrich the soil.