AS India becomes more urbanised, a major problem it has to confront is the municipal solid waste (MSW) that cities and towns generate. India today produces 0.3 kg of MSW per person per day. This figure is more than three times higher than that in more developed countries. The conventional wisdom is that such urban waste should be incinerated to generate power. The so-called waste-to-energy route, drawn from the experience of Western countries, is undesirable on many counts. India must adopt a more elaborate route that entails diligent sorting and separation of the waste, retrieval for recycling, extensive use of biodigestion, and high-temperature disposal of the residue.
Advances in biotechnology can make things simpler. Bacteria that eat plastics of different kinds could be harnessed to separate plastics from other rubbish.
Frugal Indians already sort and recycle a fair bit of their household waste. Old newspapers, other kinds of paper, packaging material such as cartons, beer bottles and most bits of metal are segregated at the level of the household itself and sold to the easily available kabaadiwala (buyer of waste paper, metal and glass). This is one reason why the per capita waste in India is quantitatively smaller than in Western nations.
However, rare is the Indian who would sort plastic from other waste before dumping garbage into the trash bin. Indian waste is typically moist food waste (up to 60 per cent). This lends itself eminently to biodigestion, yielding methane and compost. But collecting this separately from the plastic and other material it comes mixed with is a chore. Urban authorities and environment-minded non-government organisations would need to come up with workable plans to separate all kinds of plastics from other waste.
Some plastics can be rendered biodegradable by adding the right sort of additives during the manufacturing process. The increase in cost is negligible and the government would do well to mandate biodegradability for all plastics that can be made biodegradable. Instituting a purchase price for plastics is another solution. Even if the relatively well-off could not be bothered to sort and store plastic material in large enough volumes to sell to buyers, others would come forward to retrieve such plastic from the trash and sell it to whoever would offer the best price.
Amassing enough organic waste from households to make a biodigester viable is one challenge. Making compressed biogas and using it for cooking or producing electricity is another. Cooking is the most energy-efficient use of the gas produced: the heat it generates, when burnt in an efficient stove, gets used to heat the food. Burning the gas to heat up water and produce steam and piping the steam to drive a turbine entail loss of heat all along the way and is suboptimal. India does not yet require much of residential heating and so that would not count as an efficient use of the gas derived from biodigestion.
An Indian multinational firm has announced plans to set up compressed biogas (CBG) plants using sugarcane waste; one of them has been commissioned in Uttar Pradesh.
Municipalities that invest in collecting and transporting organic waste from households to CBG plants would attract investment in the sector and can create some jobs to boot. Considering that CBG plants generate both gas and compost that serves as manure, a sizeable investment in CBG can save tens of thousands of crores of rupees in fertiliser subsidy and reduced import of natural gas and ammonia.
The Central Government can offer a share of this collective national saving as incentives for municipalities to initiate organic waste collection and transportation to CBG plants.
Once CBG is demonstrated to be a viable business, with some subsidy for the collection and supply of organic waste as the raw material, it would emerge as a competitive business with multiple players, incentivising technological upgradation and cost efficiency.
Incineration of the remaining waste is the ticklish part. Right now, cities tend to create large garbage dumps that develop into landfills that grow into mountains that reek of noxious decomposition, leach toxins into the groundwater and attract swarms of scavenger birds. Incineration is preferable to creating a compacted trash competitor to Mt Everest in every large city.
However, incineration at low temperatures runs the risk of producing dioxin, a very toxic substance that can seriously damage the health of those unfortunate enough to live in the vicinity of this kind of a waste-to-energy plant.
An alternative that has been deployed on the ground in Pune is a high-tech solution: plasma arc gasification. High-voltage electricity is passed between two electrodes, creating an arc through which an inert gas is passed to create temperatures of the order of 14,000°C. The gas is then passed through a sealed chamber containing the solid waste, which then yields gas and slag, besides heat. The gas can be used for producing electricity, and the slag can be sent to the landfill as a compact form of waste.
Advances in biotechnology can make things simpler. Bacteria that eat plastics of different kinds could be harnessed to separate plastics from other rubbish. Different solvents could possibly separate out metals. The remaining organic matter could be dried and chopped into pieces to serve as fuel in kilns of, say, cement plants. High-temperature incineration would avoid the production of dioxin.
As India prospers and becomes ever more urban, the amount of municipal solid waste generated would go up from around 150,000 tonnes per day at present. If the Indian urban population grows to 70 crore from today’s estimate of 50 crore, and the amount of waste generated goes up from 0.3 kg per person per day to 0.5 kg, the waste generated would more than double to 350,000 tonnes per day, enabling larger economies of scale in every operation.
India should prepare now to tackle its mountains of municipal waste in the most sustainable and health-friendly way possible.
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