Mainstreaming Climate Smart Strategies in the Sanitation Sector in Asian Cities

There is a high correlation between urbanisation and the emission of greenhouse gases. Landfills and sewers in cities generate 15% of methane emissions; this sector offers immense possibilities for the mitigation of methane emissions in Asian megacities. Capturing methane by efficiency improvements in the working of both sewage treatment plants and sanitary landfills has co-benefits in terms of both public health as well as mitigating climate change. The linking of climate change strategies with improvements in the sanitation sector, particularly in the megacities of South and South East Asia, is analysed.
Cities cover less than 2% of the earth’s surface, but consume 78% of the world’s energy. The International Energy Agency (IEA) estimates that urban areas currently account for more than 71% of energy-related greenhouse gas (GHG) emissions, mainly because of the concentrated and increased consumption of energy for transport, industry, and heating or cooling homes and offices. This proportion is expected to rise to 76% by 2030.

The focus of the world’s response to climate change has so far been on nation states. Until the Paris Agreement of December 2015 on mitigating greenhouse gases and the Kigali Agreement of October 2016 on reducing the emission of hydrofluorocarbons, the inability of nation states in brokering comprehensive agreements regarding slowing down global warming resulted in inadequate positive action. The emphasis is only now shifting to how cities, and in particular how megacities, are and will be the focal points of climate change intervention.

Cities and Climate Change
The presence of trade, commerce, culture, governments, and transportation continues to make cities centres of large habitations. Cities cover less than 2% of the earth’s surface, but consume 78% of the world’s energy. The International Energy Agency (IEA) estimates that urban areas currently account for more than 71% of energy-related greenhouse gas (GHG) emissions, mainly because of the concentrated and increased consumption of energy for transport, industry, and heating or cooling homes and offices. This proportion is expected to rise to 76% by 2030. As long as the present trend of urbanisation continues, it is unlikely that energy and fossil fuel consumption by cities, and the resultant GHG emissions, will decrease.

At the same time, since megacities (cities having a population more than 10 million) are nearly all built along coasts and/or river banks, they are particularly vulnerable to the effects of climate change. Increases in sea levels and large storm surges can threaten crucial infrastructure in megacities. The financial effects of major disruptions in the normal business operations of any city can be even more disastrous than the physical effects. In addition, rising sea levels as a consequence of global warming could have an impact on agriculture, water resources, and fisheries. These impacts will, in turn, further affect cities in ways that are difficult to predict.

As of 2016, of the world’s 31 megacities, as many as 17 were located in Asia, of which the People’s Republic of China (PRC) alone is home to six, and India five (Table 1). By 2030, the number of megacities worldwide is projected to rise to 41, of which Asia would have 23 (United Nations 2016a: 4).

In addition, amongst the fastest-growing cities, as many as 40 are located in Asia, 20 in China alone, with an average annual growth rate of 6% (United Nations 2016a: 6). During the next decade, several of the biggest cities in South Asia, including Mumbai, Kolkata, Dhaka, Chennai, and Karachi will rank amongst the largest in the world. In addition, Asian megacities have expanded functionally in a metropolitan region and tend to form huge, mega urban regions.

Therefore, not only is Asia home to the largest number of megacities and mega urban regions, it continues to urbanise fast and has the largest number of the fastest growing cities.
Water and Sanitation
For these fast-growing Asian cities and regions, access to and the adequate provision of water and sanitation services (WSS) will continue to be an essential requirement for maintaining basic living conditions and protecting public health. It would also be a challenge to ensure that these services remain sustainable, while being universalised for a growing population. Yet, climate change concerns have rarely been linked to sustainable water supply and sanitation facilities, in particular to sewage treatment and solid waste management strategies.

The commitment adopted by the international community, through the WHO–UNICEF millennium development goals (MDGs), was to halve the proportion of the world’s population without access to safe drinking water and adequate sanitation by 2015. In 2000, around 1.1 billion people (17% of the world’s population) lacked access to safe drinking water, while around 2.4 billion, or 40%, had no adequate sanitation.

The world made significant progress towards meeting the drinking water targets, but not sanitation (UNICEF and WHO 2015: 5).

The MDG targets did not specify any reduction in inequalities between the rich and the poor. Large disparities in access, availability, and, in some places, even in affordability continue to exist in both water and sanitation services.

In addition to issues of access, availability, and affordability of sanitation services in megacities, it is only now that there is a general agreement that climate change and urbanisation, the two most important phenomena of the 21st century, are inextricably linked. The effects of urbanisation and climate change are in fact converging in dangerous ways.

This article analyses the linking of climate change strategies with improvements in the sanitation sector, that is, improvements in primary waste water treatment and the efficient treatment of municipal solid waste, especially in the fast-growing cities of South and South East Asia.

Cities in East and North East Asia have had higher levels of population connected to the sewerage system. For example, Tokyo’s installed sewerage has grown with the population and development of the city over the years, such that all of its over 9 million people are connected to the sewerage system. In contrast, in Delhi, as of 2016, only a little more than 50% of the population was connected.

Methane and Urban Waste
The prime environmental concerns in the sanitation sector in the South and South East Asian region continue to be sewage and solid waste disposal.

This sector also generates non-CO2 GHG emissions, as the breakdown of organic waste releases the simplest hydrocarbon, methane. If allowed to leak into the atmosphere before being burnt, methane traps the sun’s heat and contributes to global warming. Non-CO2 GHGs are more potent than CO2 molecule for molecule. The Intergovernmental Panel on Climate Change’s Fifth Assessment Report stated that methane has a global warming potential (GWP) of 34 compared to CO2 over a 100-year period (IPCC 2013). Methane contributes approximately 20% to the annual increase in GHGs in the atmosphere, and is classified as a short-lived climate pollutant (SLCP). In addition, methane not only has a direct influence on climate, but also has a number of indirect effects, including its role as a precursor to the formation of tropospheric ozone.

Methane emissions are expected to grow by as much as 19% over the next 20 years (Pilot Auction Facility 2013; US Environmental Protection Agency 2013: iii–30). Atmospheric methane has already reached a new high of about 1,845 parts per billion (ppb) in 2015, and is now at 256% of its pre-industrial level (WMO 2016).

Although the oil and gas sector is the largest contributor to methane emissions, the environmental concerns from cities arise from the fact that landfills and sewers in cities contribute approximately 15% of global methane emissions, and also pose serious public health hazards. Total methane emissions in the urban waste sector are entirely driven by the size of the urban population. Therefore, cities in South and South East Asia, which are emerging as megacities and are currently viewed as environmental hotspots, actually offer huge possibilities and opportunities for improvements in the sanitation infrastructure and resultant mitigation of both CO2 and non-CO2 GHG emissions.

Asia is the largest contributor of global methane emissions (EPA 2013). The methane emissions trajectory for Asia is nowhere near slowing down. Within Asia, the problem of methane is a lot more serious in South and South East Asia owing to rapid urbanisation.

For example, India’s methane emissions are considerably higher than the global average of 15%. At 6%, emissions from solid waste in India are also higher than the global average of 3% (Parvathamma 2014: 10).

An aggressive reduction of methane emissions, together with action on black carbon, can substantially slow down the rate of climate change over the next few decades. It would slow global warming by approximately 0.4–0.50 C by 2050. It is estimated that measures to target methane alone would lessen warming by approximately 0.30 C by 2050 (Climate and Clean Air Coalition 2013: 5).

Cities have the potential to be centres of innovation to deliver cost-effective solutions for the mitigation of methane emissions. The case for the efficient working of sewerage systems and sewage treatment plants (STPs), as well as landfills in cities, is far more compelling in terms of climate change and public health for cities in South and South East Asia than it was for cities in East Asia half a century ago.

Most of the discussion on water and sanitation completely marginalises the issues of sewerage and climate change, based on the understanding that treatment facilities are far too expensive for most developing countries.

It must be acknowledged nevertheless that sewerage systems have a massive impact on both public health, especially children’s health, as well as on the climate and environment. The importance of a proper disposal and management system for sewage cannot be overemphasised even in habitations that have on-site sanitation facilities such as septic tanks and pits.

Reducing Methane Emissions
Methane is emitted during the handling and treatment of domestic and industrial waste water, through the anaerobic decomposition of organic matter. Capturing this methane as an energy resource is imperative for mitigating climate change.

After its capture, methane can be used for cooking or for electricity generation, as the raw biogas after purification can yield pipeline quality biomethane. As a major component of compressed natural gas (CNG), it can also be used as an eco-friendly fuel in vehicles. This can benefit many Indian cities that largely run their public transport fleet on CNG.

It is striking that most Asian cities do not have programmes to capture methane, given the uses it can be put to and the threat it poses to our planet if allowed to escape as a GHG. The importance of not allowing the methane from large STPs to flare has not gained the attention it deserves, although methane mitigation measures are not only cost-effective, they also contribute to improvements in air quality.

In most South and South East Asian cities, plagued by erratic power supply, most STPs run neither to their optimal efficiency nor optimal capacity. The reasons are not far to see, as the energy requirements of running STPs are huge—for pumping and other processes—and since their power requirements are rarely fully met, the easiest solution for the water and sewage utility or the service provider is to discharge the untreated/semi-treated waste into a waterbody. That rivers and lakes have then become cesspools of water pollution wherever the city’s untreated sewage is being discharged is stating the obvious. In coastal megacities too, a major contributor to marine pollution is the discharge of untreated/semi-treated sewage. The lack of sewerage systems and waste water treatment plants is a major threat to the oceans (United Nations 2016b).

Under such circumstances, using the methane from waste to meet the energy requirements of the STPs would ensure that STPs would run round the clock. This would not only result in a huge saving in energy costs, but would also generate environmental benefits due to the reduced consumption of fossil fuels. The energy costs in running STPs are usually taken as fixed by any state-run water and sanitation utility/service provider; attempts are rarely made to decrease their energy consumption and the resultant energy costs.

Substantial savings can occur when initial investments are more than offset by consequent reductions in cost. What is more, such computation of cost savings usually do not account for the economic gains associated with the direct health-related benefits (for example, costs avoided due to lesser number of cases of excreta-related diseases) as well as the indirect health benefits (for example, productivity gains from better health). They also do not include benefits unrelated to health (for example, time and cost savings due to better accessibility to sanitation and other services) and, most importantly, do not include climate and ecosystem impacts, which are extremely difficult to compute.

In Delhi, for instance, the monthly energy cost of running 20 STPs is as high as $1 million. An assumed 20% reduction in energy costs would ensure a saving of $0.2 million a month, or $2.4 million a year.2

A modest 20% reduction in the energy cost of running STPs and a 20% increased share of renewable green energy along with a reduction in GHG emissions can make cities drivers of climate change mitigation.

The Lack of Pipelines
Modern STPs have been constructed across several cities in Asia in recent decades. The problem though is the lack of sewerage pipelines to channelise the sewage or waste water to the STPs for treatment. Where such sewer lines do exist, they are often clogged.

The non-functioning network leads to the dual problems of sewage overflows and underutilised STPs. It is an irony that in megacities with less than 50% of the population connected to the sewerage system, several STPs remain underutilised. The discussion on the sunk capital costs of underutilised STPs is rarely a part of the sanitation debate. In most South Asian cities, such as Delhi or Karachi, at least 40%–50% of untreated or semi-treated sewage flows directly into storm water drains into the river/sea. Yet, a detailed analysis would show most STPs working way below their installed capacity. The authorities in Shenzhen, China, have constructed 33 new STPs, but 4,600 km of sewage lines are still needed, and approximately 9,30,000 tonnes of untreated waste water is still being discharged into rivers every day.

In Delhi, almost 50% of the population lives in unauthorised or illegal colonies generating sewage that is not transported by sewers to the STPs. Nearly 60% of Mumbai’s population lives in slums, half of which lives in authorised slums with some sanitation facilities, but the other 50% does not have any access to the sewerage system. Even in slum habitations where the residents have access to some on-site sanitation facilities, major issues of faecal sludge and septage management persist. A report submitted by the Central Pollution Control Board (CPCB) to the National Green Tribunal states that in India only 40% of the sewage is transported to STPs, while the remaining 60% is directly discharged on land or into
a waterbody.

In Dhaka, nearly one-third of domestic effluents do not receive any kind of treatment. About 30% of the population is not covered by a sewerage system. The city has only one STP with a capacity of 1,20,000 m³ per day. Indonesia has one of the lowest sewerage coverage levels in Asia, with only 2% of the population having access to the sewerage system and sewage treatment. The inadequate number of STPs combined with poor connectivity and the poor operating conditions of existing plants and the inability to use an important resource like methane has an adverse impact both on the health of the local populace and the environment. Clearly, improvements in the conveyance system are required for STPs to run on full capacity and with greater efficiency. The generation of methane from STPs is directly related not only to full capacity utilisation but also to the efficient running of STPs.

Hurdles and Community Benefits
Yet, several hurdles still exist in capturing methane from STPs: first, many STPs built in the last three decades were never built with the intention of utilising this resource. Methane as a by-product was just flared off. However, redesigning and retrofitting of these STPs with bio-digesters can easily be done for methane recovery. Cost-effective technology for this is readily available even in low-income countries.

Second, some STPs continue to run not on biological processes, but on highly inefficient physio-chemical processes rendering the production of methane virtually impossible. Most sewers also contain a variety of toxic and non-biodegradable substances, making their treatment less effective and more costly. However, here too, cost-effective technological solutions exist.

Third, STPs in megacities often receive storm water as sewage since storm water drains are not segregated rendering anaerobic digestion ineffective. The solution here is segregating storm water drainage from the sewerage system, especially in coastal cities.

Replacing open sewers with centralised sewers and treatment facilities not only increases the generation of methane, but also dramatically reduces the transmission of human disease. The health benefits of disease reduction are actually even larger than the benefits of reduction of GHGs, and the direct and indirect health-related economic benefits of improved sanitation far outweigh the costs of improvements in sewerage systems and sanitation. The investment in sewage infrastructure to improve the existing waste water treatment systems results in huge public health benefits.

The inertia in generating methane from STPs could be overcome if the process is encouraged and mandated by law. Countries in South Asia could actually leapfrog the climate change curve by making mandatory the capture of methane from STPs and landfills. If the utilisation of bricks from fly ash, a waste product generated by coal-fired power plants, can be made mandatory within a particular radius of the thermal power plant, there is no reason why STPs cannot be mandated to capture methane and supply fuel for the STPs. This would have the added advantage of supplying fuel for cooking purposes to at least 300–400 households in their vicinity. The change in the approach to treat methane as a useless by-product to a major resource will be the beginning of breaking a vicious cycle and moving to a virtuous cycle that can change the way that STPs function and the way citizens view STPs.

In India, some smaller municipalities, such as the Tambaram municipality in Tamil Nadu have set up bio-methanation plants in order to convert solid waste into methane. The bio-methanation programme in Tambaram followed the success of the municipality’s Namma Toilet Project, and was meant to end open defecation by putting up toilets in public places. Methane gas naturally generated from the sewage is directed through an overhead pipe, which is then routed through smaller pipes to 12 conventional stoves in a kitchen located within the complex. The plant is a boon for women in the adjoining slums, who benefit from the cooking fuel they get.

Oftentimes, opposition from local communities constitutes one of the biggest barriers in making affordable methane reduction technologies work, as STPs and landfills are viewed as problems and not as solutions by the community living within the vicinity of the STPs.

But the involvement of the community in the Tambaram project has clearly shown that in addition to technocratic solutions, for a project to be sustainable, it is important for the community to view STPs not only as a pollution control/abatement project but also as having benefits, one that supplies energy to their households.

Utilising Methane from Landfills
Municipal solid waste (MSW) has become one of the most important by-products of an urban lifestyle, and globally, the volumes of waste generated are increasing even faster than the rate of urbanisation. There is a strong correlation between urban solid waste generation rates and GHG emissions, but solid waste disposal sites are rarely seen as providing opportunities for reduction in methane emissions and for energy solutions.

Landfills produce methane and other gases through the natural process of bacterial decomposition of organic waste under anaerobic conditions. Landfills are the third-largest generator of anthropogenic methane emissions and contribute about 12% of total global methane emissions (US Environmental Protection Agency 2013). Methane emissions from landfills vary by country depending upon the population size, quantity and composition of the waste, climatic conditions, and waste management disposal practices. Since the composition of organic waste in municipal solid waste in low-income countries tends to be higher than developed countries, the resultant methane production from landfills would also be higher in these countries.

Capturing gas from landfills and using it to produce electricity are based on well-tested technology options, which are also low cost. A system of horizontal and vertical extraction gas wells and pipes can collect the landfill gas, and send it to the boiler or turbine, where it is combusted to generate heat/electricity. A pilot plant by Western Paques found that 150 tonnes per day of municipal solid waste could yield 14,000 cubic metres of biogas with 55%–65% methane, which could generate 1.2 MW of power.

It is often argued that capturing landfill gas can significantly reduce methane emissions in large landfills, but not in smaller landfills as they are not regulated. The separation and treatment of bio-degradable municipal waste by promoting recycling and composting needs to be encouraged as a part of better waste management practices. Here again, a more efficient solid waste disposal system can actually lead to a more efficient methane emissions reduction programme. Engineered sanitary landfills ensure that waste is compacted and covered, and are constructed with gas and leachate collection systems.

The higher the degree of engineering at the sanitary landfill facilities, the more efficient would be the gas collection system, which can reach a collection efficiency as high as 85%. Hopefully, a focused programme on sensitisation of the municipal authorities will drive home the advantages of engineered sanitary landfills.

The problem in South and South East Asia is that there are either open dump sites or basic landfills, sometimes called managed dump sites. Sanitary landfills rarely exist and “garbage hills” are euphemistically called landfills. Nevertheless, even these garbage hills generate methane, as has been the case in Mumbai (Deonar) and Delhi (Ghazipur and Bhalswa). These facilities generate relatively small amounts of methane, and yet have a collection efficiency of about 70%. Methane extraction infrastructure can be installed even in these sites. The added advantage would be a reduction of air pollution in the vicinity of these “garbage hills.”

Public pressure would then also mount to move away from open dumping or managed dump sites towards engineered landfill solutions, wherein recycling and composting would also be an integral part of the solution. However, the process of making cities feel that they stand on the threshold of being the harbingers of climate change strategies has still to take off in South and South East Asia.

It is absolutely clear that unless and until each megacity begins to worry obsessively about its sewage and its solid waste, it cannot save its rivers or even itself. The efficient disposal of sewage and municipal solid waste could lay the foundations for achieving not only the MDGs for sanitation but also for other health-related MDGs such as child and maternal mortality. Improvements in the sanitation sector are inextricably linked with the reduction of non-CO2 GHG emissions, particularly methane. In fact, methane mitigation has the largest potential across all non-CO2 GHGs. Arguably, the greatest challenge in the sanitation sector is also the biggest opportunity in forging the links between global climate change and positive actions to improve the efficiency in water and sanitation services at the city level. Climate change and public health benefits are the reason to promote a sustainable urbanisation pattern and transform the sanitation sector into a low-cost, energy-efficient sector.

However, the win–win benefits from the mitigation of methane emissions and public health have so far been overlooked in the wider climate change and air quality debate. While cost-saving estimates for the green energy generated can be undertaken, the resultant public health benefits are huge and extremely difficult to quantify. Upgrading the primary waste water and municipal waste treatment facilities will go a long way in not only slowing down the rate of climate change over the next several decades, but also in protecting the people and regions that are the most vulnerable to climate change.

1. Global warming potential (GWP) values compare the capacity of a gas to contribute to an energy imbalance, or      warming, relative to carbon dioxide. Carbon dioxide is the reference gas; its GWP is set at one.
2. This figure does not include the energy costs of running two STPs, which is borne by the power utility/service provider.


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Naini Jayaseelan ([email protected]) is Secretary, Inter-State Council Secretariat, Government of India.