City waste: Plan energy production

From its waste of 1.3 million tonnes a year, Bengaluru generates about 4,274 tonnes of methane gas per year.

The recent incidence of inflammable gases emanating from the waste dump sites at Lakshmipur and Bingipur in fringe areas of Bengaluru should be viewed as an eye opener. These incidences demonstrated naturally the amount of energy trapped in the municipal solid waste (MSW) we generate every day.

The coverage of these incide-nces in the media, however, focussed mainly on the callous and unscientific dumping practices, rather than portraying the pote-ntial energy trapped in it. When Sir M Visweswaraiah, the architect of engineering marvels, saw the Jog Falls, he exclaimed “what a waste”, realising the enormous amount of energy being wasted in the falling waters.

The result of this exclamation was the Sharavathi Hydroelectric Project. If he were to be alive today, he would have perhaps exclaimed the same way looking at the huge piles of MSW and the energy being untapped from it. In recent years, MSW management has become a burning issue in Bengaluru.

Dumping has caused many problems to the nearby villages. Nuisance to urban population in several areas of the city is no less small. Variety of problems like foul smell in and around the area, increased population of pets, flies and vermin, stray animal menace, choking of storm and sewage drains, and spread of diseases are unleashed by the MSW littering.

Other externalities like formation of leachate and landfill gas leading to water and air pollution are also a matter of serious concern. Aesthetic value of the land in the vicinity of the du-mping sites is also affected. All these issues not only point to our improper management of waste but also on the negligence of the potential energy hidden in it.

Where is the energy in waste? The composition of an urban MSW would normally contain 51 per cent organics, 17.5 per cent recyclables like paper, plastic, metal, and glass and 31 per cent inerts. Its moisture content is 47 per cent. When this waste is landfilled, the organic fraction in the waste slowly decomposes. In this process, landfill gas is formed which consists of about 60 per cent methane (CH4) and 40 per cent carbon dioxide (CO2) with other trace gases.

This is how the inflammable methane gas emanated and still emanating from the Lakshmipur and Bingipur landfill areas. However, percentages of the gas constituents differ spatially due to waste composition, age, quantity, moisture content etc. A total of 40-60 metric tonne of methane is emitted from landfills worldwide accounting for about 11-12 per cent of the global anthropogenic methane emissions.

The methane thus generated, with proper processing and managing, can be used as a biofuel to lessen the demand for LPG. If it is not tapped properly, methane would add to greenhouse gases which produce threat to the ozone layer, which protects the earth from the harmful ultraviolet radiations.

Compared to carbon dioxide, methane has 25 times more global warming potential and more than 50 per cent of the gas emitted by the solid waste is methane. Hence, there is an urgent need to harness this gas for human benefit.

Bengaluru scenario
The massive municipal waste output in the city is a key issue to be addressed for the better planning and growth of the city. The MSW generated here is about 1.385 million tonnes per year out of which nearly 35 per cent has either recyclable or recoverable value. Though the BBMP has been trying for sustainable management of this waste, the rate at which MSW is generated is colossally huge when compared to the infrastructure they have built to handle/recycle it.

Very few bio-methanisation plants have been put up and hence, are inadequate to pro-cess this huge waste. The present population of about one crore is likely to go up on a rapid scale due to large influx of people from all parts of the country, which only would add to the woes of waste management.

The BBMP spends about Rs 415 crore annually out of its Rs 6,729 crore budget towards SWM. However, the fund is inadequate and government needs to increase the allocation. Also, the BBMP could augment this funding by raising the cess from residents, hotels, marriage halls, industrial establishments etc to match the allocations required for efficient management of waste.

An estimate based on the guidelines suggested by Intergovernmental Panel on Climate change (IPCC, 2000) and the basic data from BBMP (SWM Master Plan, 2008) suggest that Bengaluru’s MSW can generate about 4,274 tonnes of methane gas per year (considering the average population of Bengaluru to be around a crore and per capita waste generation to be around 0.35Kg/day).

This means around 3,00,986 LPG cylinders – considering 14.2Kg gas in each cylinder – could be saved annually if the energy potential of the municipal waste is properly harnessed. The residue after harnessing bio-gas could be used as organic manure. These efforts will in turn help in environmental conservation besides minimising the nuisance of waste. The dream of “Swatch Bharath” can be greatly realised through this kind of efforts.

(The writers are from the Department of Geology, Bangalore University)