by Isher Judge Ahluwalia , Utkarsh Patel
Recycling, composting and biomethanation will not only make landfills unnecessary, they will also help
reduce greenhouse gas emissions.
In these columns, we have been presenting the public health implications of different aspects of solid
waste management activities in Indian cities. Today we spell out how such improvement will also reap
dividends by mitigating global warming.
Greenhouse gases (GHGs) create a natural blanket around the Earth’s atmosphere by preventing some of
sun’s heat energy from radiating back into space, thus keeping the Earth warm. Over the last
century-and-a-half, human activities have added considerably to GHGs in the atmosphere, and that
to result in global warming. Activities involved in the management of solid waste generate (GHGs) such
carbon dioxide, methane, and small amounts of nitrous oxide. The global warming potential of methane is
times as much and nitrous oxide 298 times as much as that of carbon dioxide, over the long run (100
GHG emissions from solid waste disposal as reported to the UNFCCC in 2015/16 by India increased at the
rate of 3.1per cent per annum between 2000 and 2010, and by China at 4.6per cent per annum between 2005
and 2012. However, there is reason to believe that for both India and China, the estimates of emissions
from the waste sector are underestimated for not considering emissions from the transportation of waste.
Much of the problem arises because we mix biodegradable waste with other waste at the point where waste
generated. This increases the volume that has to be transported as the waste is hauled all the way to
landfill sites. The increased fuel usage in transportation results in more emissions.
The volume of waste sent to the landfill sites can be reduced if biodegradable waste is processed
through aerobic decomposition with the help of microbes or earthworms (vermicomposting) to produce
or organicfertiliser. Compost helps store carbon back in the soil. Its usage reduces the need for
fertilisers which emit large quantities of nitrous oxide — both during production and in application—
thereby helps mitigate emissions. Compost also improves moisture retention in the soil.
We are losing out on mitigation through composting because at most only two per cent of the municipal
solid waste in India is composted. The Supreme Court order of 2006 directed fertiliser companies to
co-market city compost with chemical fertilisers. However, the government incentive of market
assistance for city compost at Rs 1,500 per tonne to fertiliser companies is no match for the capital
subsidy and transport subsidy provided to chemical fertilisers, which renders compost uncompetitive
vis-a-vis chemical fertilisers.
An alternative to composting for biodegradable waste is biomethanation or anaerobic decomposition.
Biomethanation generates biogas which is a substitute for fossil fuel and produces slurry which is an
excellent organic fertiliser, both helping to mitigate global warming. Local processing also means that
biomethanation saves on transportation. Very few Indian cities are trying biomethanation because
segregation at source and feeding biodegradable waste to the plants in time remain a major challenge.
Recycling of waste also helps reduce GHG emissions because the energy required to manufacture a product
using virgin materials is higher than when using recycled materials. While India has had a tradition of
recycling paper, glass, metals, etc with the engagement of the informal sector, lack of segregation
in the way of realising the full potential of recycling.This is particularly true for paper that soils
easily when waste is mixed. As a result, only 27 per cent of paper in India is recycled, compared with
per cent in Japan and 73 per cent in Germany (CPPRI, 2013). Recycling requires up to 50 per cent less
energy compared to production of paper based on wood pulp, and it also saves trees from being cut.
The non-biodegradable and non-recyclable waste other than hazardous waste (batteries, CFLs, etc), can
converted into Refuse Derived Fuel for use in high-temperature furnaces, for example, in cement kilns
power plants. Technologies are also available for controlled incineration and/or gasification for energy
recovery from this waste. These are commonly referred to as “waste-to-energy” plants.
In an earlier column (‘Don’t just light the fire’, IE, May 31, 2017), we had pointed out that
unsegregated municipal solid waste to generate electricity in Indian cities is unsustainable. The low
calorific value of the unsegregated waste and the need for auxiliary fuel input makes these plants
financially unviable, besides generating more greenhouse gases. On the other hand, incineration of mixed
waste in the absence of auxiliary fuel can release dioxins and furans which are severe air pollutants.
This has to be countered by installing appropriate filters in these plants.
The Solid Waste Management Rules (2016) have laid down clear guidelines on permissible emission norms.
There is a need for real-time monitoring and open access to emissions data to ensure enforcement of the
norms. Both the Central Pollution Control Board and the National Green Tribunal have been working
these goals. But if the regulatory framework is not considerably strengthened, such plants will only end
up converting solid waste into air pollution and leaving a larger carbon footprint.
If incineration is not desirable or acceptable, the solution is not simply to dump untreated mixed
at landfill sites. Landfills in India are neither scientifically engineered nor scientifically closed.
They serve as open dumpsites. The discarded plastics in the mixed waste are a major contributor to
dumpsite fires. Disposal of mixed waste including biodegradable matter (sometimes as high as 60per cent)
in these dumpsites provides a perfect anaerobic environment for generation of methane and leachate. One
tonne of biodegradable waste releases 0.84 tonne of carbon dioxide equivalent emissions if left to
The untreated disposal of mixed municipal solid waste at landfill sites is around 80per cent for Mumbai
and Chennai, 50-60per cent for Delhi and Bengaluru, and 35per cent for Pune. This implies that Mumbai
emitted 921 k-tonne of carbon dioxide equivalent of GHG gases from landfill sites in 2016, equal to
emissions from 1,96,000 typical cars. For Delhi, the estimate is 137,000 cars. Bioremediation offers a
relatively quick and inexpensive mitigation instrument for reducing the GHG emissions from landfill
through aerobic decomposition of organic fraction of the waste (‘A city laid waste’, IE, June 28, 2017).
There are lessons to be learnt from other countries. GHG emissions from solid waste have been declining
Germany and Japan. A ban on landfilling of non-pre-treated waste in Germany has led to 47 per cent of
waste being recycled, and 36 per cent incinerated. In Japan, 75 per cent of the waste is incinerated,
while 21 per cent is recycled. The regulations in both countries ensure that incinerators have
state-of-the-art emission control technologies, and the directly landfilled municipal solid waste is as
low as oneper cent.
India needs to get its act together to improve its municipal solid waste management with the triple
objective of resource recovery, improving public health conditions and mitigating the risks associated
with human-induced global warming.