Cities take the lead on mitigation

Scientists predict that climate change could reduce the flow of the river Seine by 15 to 50 percent © Jdanne

The COP21 meeting in Paris is an opportunity for city governments and water professionals to highlight the role of practical interventions in combatting greenhouse has emissions. By James g. Workman.

As tens of thousands of climate change delegates descend on the 21st Conference of the Parties (COP21) in Paris, a small fraction now recognise how water management isn’t just figuring out how to cope with extreme weather, it is also about how smart water use can reduce the emissions that force extreme volatility in the first place.
Plugging leaky pipes and lowering demand for water saves energy and reduces emissions. But even more greenhouse gases are captured when cities become savvy about treating and capturing value from raw sewage. Indeed, to the extent that it fuses adaptation and mitigation, water may be both a game changer and dealmaker.
“There is a stronger focus on adaptation than mitigation in the water sector, when the two are really intertwined,” says Andrés Rojo, an urban water efficiency professional in

The potential conversion of untreated sewage emitting around 40 kg CO2e per year per person into “zero emission” systems–if designed right–could be leveraged in the global climate mitigation talks to identify new funding

Corinne Trommsdorff, Programme Manager, the International Water Association

Corinne Trommsdorff, Programme Manager, the International Water Association © IWA

Mexico. “Climate change is compelling us to face problems that we have been deferring to a future time, when dealing with them would be exponentially more difficult.”
The water-carbon linkage, long ignored, can no longer be denied. In 1994, some 196 countries ratified the UN Framework Convention on Climate Change (UNFCCC). Parties to the UNFCCC acknowledged human activity drives global warming, and pledged steps to combat it. Yet for more than a decade, water played almost no part in annual discussions about tactics or deadlines. Water was off the agenda, banished literally to the coffee table.
Only gradually, out in the corridors, did water professionals start to find a climate voice. First, atmospheric scientists noted the volatile chemical compound behind climate ‘forcing’ was not methane, nitrous oxide, or carbon dioxide, but hydrogen dioxide. The fast-evaporating water vapour down here gathers, magnifies and complicates the greenhouse effect up there.
Later, people began to concede that water is the medium through which climate manifests itself. Nearly every part of the global warming litany that scared people–aquifer intrusion, protracted droughts, flash floods, land subsidence, melting snowpacks, falling reservoirs, desiccated farmland, urban heatwaves–came down to the loss of fresh water.
Governments braced for these shocks. They scrambled to ‘climate proof’ society through engineering feats or early warning systems until an urban-led ‘resilience agenda’ gathered cohesion, attention, political support, and money. So as mitigation efforts stalled, cities raised water management funds. Now, water professionals have forged an inextricable link between the two.

Cities at the centre

Jean-Pierre Tabuchi-min
Jean-Pierre Tabuchi, Head of SIAAP’s Health and Sanitation Division © SIAAP

Unlike national governments at the COP, cities don’t have the luxury or political insulation of delaying action. And more and more are recognising the potential of better water management to reduce emissions by launching their own innovative programmes for wastewater treatment and climate change mitigation.
“Climate change is often framed in terms of a geopolitical discourse among countries but we’ve found that the most responsive interventions come from cities,” says Corinne Trommsdorff, Programme Manager at the International Water Association. “Cities set and hold themselves accountable to near-term targets; they need solutions now. As they do, cities recognise the real opportunity to reduce humanity’s carbon footprint through upgrading or reforming their water and wastewater systems.”
Paris, the host city for the COP21 meeting, is itself looking to reduce greenhouse gas emissions through innovation in wastewater treatment. The traditional approaches to disposal–many first pioneered in the French capital in the 1830s–process the waste of 9 million inhabitants through six wastewater treatment plants operated by the metropolitan area utility, SIAAP. But climate change is a threat to the amount of runoff available for waterborne sewerage.
“Scientists project that in the years ahead, climate change could lower our flow by 15 to 50 percent,” explains Jean-Pierre Tabuchi, Head of SIAAP’s Health and Sanitation Division.  “That’s a huge loss of water, given the outflow, and we would not be able to keep the river in a good state.”
To cope with increased effluent, he has had to figure out how to reduce discharge into the Seine.
“We looked and looked and the best way was to reduce the input of nitrogen into the sewer system, through urine diversion and collection, in each new apartment,” says Tabuchi. He has found a reluctance to change behaviour. “Each time I meet with groups on this I face a challenge. When I share the constraints we face, no one understands. I say a man will have to pee sitting down, and everybody laughs.”
Nevertheless, to keep up with growing demand, and shrinking water supplies, Paris must start building 400,000 apartments with urine diversion toilets each year. Those not built now will compound future stress. But the water-saving strategy could gain broad support from capturing emissions that would come as a result of conversions.
Indeed, by adapting early to climate-driven scarcity, Paris may join other cities that are reducing wastewater emissions and earning carbon credits, energy, and fertiliser in the process.
Two such cities are Oslo and Stockholm, with the former, one of the first cities to capture methane from sewage treatment plants to fuel 80 buses in the city fleet, while in Stockholm, a wastewater plant at Bromma turns 10,000 tonnes of dry sewage sludge a year into 1.5 cubic metres of biogas, which is cheaper than petrol.
Jadranka Milina, Senior Executive Officer, at Oslo’s Water and Sewerage Works, stressed the need to be honest about the challenge but also the opportunity from urban wastewater. “Talk to the heart. Find strong images. Use humour,” she says. “When the city’s buses are running on the most environmentally friendly fuel available [human excrement], we reduce air pollution and CO2 emissions and you contribute every day.”
But innovation in managing wastewater emissions is not confined to the global north. When Tabuchi in Paris sought exemplary leadership in urine diversion toilets, he said he looked to cities of the developing world, including South Africa. There, a decade ago, the eThekwini Municipality introduced urinediverting toilets to the under-serviced communities of greater Durban, as part of its overall strategy to provide sanitation for all citizens. It chose to install tens of thousands of decentralised, urine-diverting dry toilets because the traditional pipe network and a treatment system for enormous supplementary volumes of sewage would have been prohibitively expensive and impractical due to the hilly landscape.
The cheaper approach still had problems. Handling and emptying burdens fell on householders, and urine infiltration risked polluting groundwater, lakes, and rivers. So five years ago, the city set out to give urine a value, by producing fertiliser and reducing pollution in a new large-scale implementation of nutrient recovery called Valorisation of Urine Nutrients in Africa, whose acronym, VUNA means ‘harvest’.
VUNA has not yet linked urine diversion to a drop in emissions. But the logic is manifest in two ways. Most dramatically, slashing waterborne sanitation requires less energy for treatment and conveyance, and thus a lower carbon footprint. A more complex equation comes from producing a fertiliser from natural ammonia and nitrates in wastewater rather than using a chemical process. “[Chemical manufacturing] uses methane as an input to the process and produces nitrous oxides which have a GHG impact of 298 times that of CO2,” says Trommsdorff. “While the energy requirements from diversion are still around four times more than chemical fertiliser production in this early development stage, the additional energy could be offset by reduced energy in water supply.”

But can it scale?

Such isolated cases offer promising, affordable options. But thousands of cities around the world, rich or poor, already use some form of treatment. Can these be maximised, upgraded or repurposed in ways that save money, capture resources, and reduce emissions. In sum, can the new approach scale?
A new collaboration could answer that question by 2019. The Water and Wastewater Companies for Climate Mitigation (WaCCliM) project, funded by the International Climate Initiative (IKI) of the German Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety, is focused on three urban pilot projects in Mexico, Peru and Thailand [see box: Three Unique Cities]. There, WaCCliM is founded on the proposition that all cities can reduce their carbon footprint through emissionreducing technologies and systems that reuse treated wastewater, recycle nutrients, while improving both service levels and the bottom line. If the approach works, it has the potential to spread.
As results emerge, the WaCCliM pilots could help frame water not as a medium of climate change, but as an affordable means to reducing the emissions that cause it.
Service expansion or replacement of urban water and sanitation assets has costs. McKinsey Global Institute estimates the world will need a cumulative investment of about US$480 billion by 2025. And retrofitting existing systems to more energy efficient designs is often an investment with a return period of 15 -20 years.
Yet experts say urban water utilities can improve their energy efficiency by around 30 percent without longterm investments. They could also reduce emissions associated with river discharge by directing treated effluent to agriculture rather than rivers and they can convert the carbon energy from biosolids into biogas, heat and electricity, covering up to 100 percent of their energy needs.
“The potential conversion of untreated sewage emitting around 40 kg CO2e per year per person into “zero emission” systems – if designed right – could be leveraged in the global climate mitigation talks to identify new funding,” says Trommsdorff.
Looking at a globally volatile future, the question is not whether local cities can afford to rethink their water and wastewater operating systems in ways that both adapt to and mitigate climate change, but whether any can really afford not to.
“The hope for the WaCCliM pilots is that they will help to validate that it is possible to increase efficiency while increasing service levels at the same time, therefore making the utilities’ operations more sustainable, environmentally but also financially, in the long term,” says Rojo, who is advising the BMUB-funded and GIZimplemented project in Mexico.
Leading up to the COP21 in Paris, water remains absent from the agenda. It is seen as competing for attention or funds. But if city governments and water professionals combine their voices behind one platform in Paris, they can demonstrate how practical and scalable interventions can achieve both water development and climate mitigation goals.

Three unique cities, one common denominator

In Guanajuato, Mexico, the linked utilities of San Francisco del Rincón provide water and wastewater services to 130,000 people. The source from wells requires only disinfection, the drainage network requires no pumping, and the treatment plant uses an activated sludge system. Even so, payments to the power grid eat up nearly a quarter of the total running costs, and emit greenhouse gases (GHG). WaCCliM found this utility could simultaneously save money and reduce carbon through more efficient groundwater abstraction or optimising the wastewater treatment and associated biogas valorisation. But the biggest surprise was how untreated sewage discharge was still responsible for a major fraction of emissions, so
that the planned improvement in coverage–even if it is not explicitly part of the project–will improve the utility’s carbon balance.
Thailand’s National Climate Change Master Plan calls for reducing GHG emission by between 7 and 20 percent by 2020. Astonishingly, wastewater treatment accounts for almost half of all emissions in the waste sector, and 4.1 percent of the country’s total emissions. That explains the interest of Thailand’s Wastewater Management Authority (WMA), which manages and operates 15 urban treatment systems,
including the plant servicing 150,000 people in Chiang Mai. Before reaching the utility, domestic wastewater is first treated by septic tanks and grease traps at individual premises. Only then are greywater, septic tank overflow and storm waters collected and pumped to an
aerated lagoon for further treatment. Yet again, energy costs–which make up more than half of WMA’s operational costs in Chiang Mai– are pushing it to reduce GHG emissions. WaCCliM found gains could come through more efficient pumping, reducing water infiltration,
and avoiding collected sewage overflows into the river. The biggest gains in emissions reductions would come from expanding coverage of sewage collection, and treating all water collected.
In Peru, 415,000 people in the mountainous province of Cusco depend on the Vilcanota system supplying about half of the city’s needs at a high pumping energy cost but the San Jeronimo wastewater treatment facility with a smart process selection requires only modest energy and has the potential to produce energy to cover both the water and wastewater utilities’ needs, once optimised. Discharge of untreated wastewater remains the main source of GHG emissions, even with treatment coverage of 83 percent.

Andrés Rojo (left) is advising the utilities at San Francisco de Rincón, Guanajauto, Mexico © SAPAF