In the fight against climate change, anaerobic digestion and biogas could take an important role as renewable energy sources. Biogas can be converted into electricity and heat through cogeneration, making it resource efficient and sustainable. But what role does biogas play with respect to climate mitigation in the urban water sector?

Potentials for greenhouse-gas reduction and energy savings in the water and wastewater sector

The impacts of climate change pose a threat towards water supply and sanitation systems. In order to ensure functioning water and wastewater management under those changing conditions, the urban water sector must find solutions to adapt to the risks brought on by climate change. At the same time, the provision of potable water and the treatment of wastewater also contribute to greenhouse gas (GHG) emissions. Water and wastewater systems are energy intensive and can account for as much as 40% of municipal energy use[1], while this energy often comes from burning fossil fuels. Water losses lead to even higher energy consumption, and untreated or poorly treated wastewater emits methane and nitrous oxide, gases with much higher global warming potential than carbon dioxide. Fortunately, there are many opportunities for improving the carbon footprint of water and wastewater companies by updating their technologies and management processes into more energy-efficient systems, as well as recovering energy and nutrients from wastewater.
This is where the implementation of cogenerators for biogas production in wastewater utilities can be of great use as, on average, the energy content of wastewater is five to ten times higher than the energy that is used for its treatment. Up to 0.56 kWh/m3 can be produced from sewage sludge in theory, however this number is significantly lower in reality, due to inefficiencies in the digestion process and electricity conversion. Biogas can be used to produce electricity, fuel or heat, either to meet the plants own demand or to be fed into a district heating grid. Generally, small plants with a capacity of <5 million liters per day cannot generate biogas in a cost-effective way, whereas plants with a capacity of >5 million liters per day can only generate electricity if digesters are integrated in the plant[2].

Global action for climate change mitigation as important field in international cooperation

The “Water and Wastewater Companies for Climate Mitigation” project -WaCCliM for short – has developed the “Energy Performance and Carbon Emissions Assessment and Monitoring” Tool – short ECAM – to measure GHG emissions and the energy performance from urban water services at a system-wide level and to identify areas of improvement.

WaCCliM is a project of the German Government, implemented by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH and the International Water Association. The aim of the project is to support the urban water sector to become climate-smart and sustainable through higher energy and water efficiency as well as reduced GHG emissions, both directly through adequate management of sewage sludge and indirectly through a reduction of energy consumption.

Mexico: Implementation of biogas technologies in a WaCCliM partner-utility |
The status quo of biogas technologies in the Mexican water and wastewater sector

The WaCCliM project is being implemented in three partner countries, two of which are Mexico and Peru. Mexico is unconditionally committed to reduce its GHG emissions by 22% by 2030 compared to a business-as-usual scenario. However, conditional commitments would allow for increased emissions mitigation of up to 36%. Mexican water utilities will need to contribute to this reduction, but they already face a difficult task in meeting users’ demands.  Obstacles like low tariffs, high water consumption and a complicated legal framework have led to unsustainable water abstraction, high energy costs, water losses and inadequate wastewater treatment. In Mexico, GIZ is working with the National Water Commission, the Ministry of Environment and Natural Resources and the National Water Association of Mexico. These partners have participated in the dissemination of the low-carbon approach in the urban water sector, including through network meetings of utilities and the development of standards for biogas and energy generation projects.

SITRATA, the wastewater treatment utility in the city of San Francisco del Rincón is adapting measures to a sustainable, low-carbon wastewater management.  The wastewater treatment plant (WWTP) is based on an activated sludge system. Currently, emissions of ~2,500 tCO2e per year are being avoided, which was achieved mostly by expanding wastewater treatment coverage from less than half of the city to more than 80%. The utility is now investigating further measures to reduce emissions and operational costs and increase resilience to climate risks in the city’s wastewater system. In this context, sewage sludge plays a significant role. Even though sludge has very little monetary value and many utilities struggle with its management, it can be a source of renewable energy that can replace fossil fuels. At the moment, biogas is only being used for the production of thermal energy at SITRATA. However, the utility is considering the implementation of a cogeneration system to convert biogas to electrical energy as this would bring along several benefits. Firstly, operational costs and GHG emissions of the WWTP could be reduced, as the utility would produce its own electricity, making it less dependent on price fluctuations of the national grid. Secondly, the utility would increase its efficiency as the biogas would not be flared.

Only a low number of WWTPs in Mexico have infrastructure for biogas capture, which hinders an effective supply chain structure and increases costs for replacement parts. However, recent studies have identified 27 large facilities with a potential for cogeneration systems for biogas use in the country. The WaCCliM project has facilitated the participation of different network meetings with other utilities that operate WWTPs with cogeneration systems. By constructing partnerships and sharing experiences for up-scaling, we hope that more utilities will follow this way.

The legislation for the production of biogas in Mexico is still under development. Until now, there is no specific regulation for the management and use of biogas. However, there are several national norms related to the topic that can serve as an orientation for the establishment of a norm that regulates the production and the use of biogas for energy generation. Regardless of this, the anaerobic treatment of wastewater is considered to have high potential in Mexico and Latin America in general: even if biogas is not used widely yet, the reduction in GHGs and good results in life cycle assessments show that the use of biogas for electricity generation is the technological option that should be privileged in the future. Therefore, it is necessary to develop a standard that contains all the aspects involved, from the conduction of the biogas, its storage, incineration, treatment and use, with special emphasis on security aspects. Furthermore, competence standards for engineers, technicians and operators of WWTPs need to be established in order to ensure the proper management and maintenance of biogas technologies in the utilities.

Peru: Implementation of biogas technologies in a WaCCliM partner-utility |
The status quo of biogas technologies in the Peruvian water and wastewater sector

In Peru, the WaCCliM project cooperates with the General Directorate for Environmental Affairs under the Ministry of Housing, Construction and Sanitation (MVCS). Supported by WaCCliM (responsible for mitigation) in collaboration with PROAGUAII[3], the MVCS has introduced Mitigation and Adaptation Plans for Climate Change (PMACCs; Planes de Mitigación y Adaptación al Cambio Climático) as planning instruments to cope with climate change within the responsibility area of water and sanitation utilities, which started seeking practical carbon emissions reduction solutions, such as the utility in Cusco, SEDACUSCO. For instance, improved sludge management has proven highly effective in the city, with multiple benefits. It has avoided emissions of ~7,454 t CO2e per year while bringing a serious local odor problem under control. Currently, the utility is installing a cogeneration system for biogas valorization. SEDACUSCO has a surplus production of almost 3,000m3 per day of biogas, which in prior times has been flared and emitted to the atmosphere.  The objective is now to recover the biogas and generate electricity for internal use, thereby saving €260,000 in annual electricity costs and avoid a further ~544 tCO2e per year in emissions.

Compared to Mexico, there is a lower number of biogas installations and cogenerators in Peru.

Several water and wastewater related measures prioritized by utilities have been included in Peru’s NDC (Nationally Determined Contributions); thus, contributing to the commitments made by the Peruvian government to reduce 20% of its GHG emissions by 2030, as well as a more ambitious target of 40%- as it was announced during the climate ambition summit in 2020.

To discuss on scaling up energy efficiency among utilities nationwide, the MVCS, with the support of GIZ, organized the “International Forum: Use of Biogas Generated in the Municipal Wastewater Treatment Plants of Peru, in the Context of Climate Change”. Sectoral decision-makers from MVCS and regulatory body, utilities´ operators, additional government entities related to the topic (Ministries of Finance and Environment), as well as representatives of the private sector and civil society, were brought together, to identify the opportunities and challenges of introducing low carbon technologies in the Peruvian sanitation sector. To date no funding programs are available. The MVCS is now integrating the climate mitigation approach into sectoral strategic plans and guidelines in order to lower operating costs, enhance operational efficiency and reduce GHG emissions in the urban water sector.

Peru offers an opportunity to apply anaerobic technology due to its warm weather, particularly in the amazon region; moreover, biogas technology can be easily imported. However, to realize the full potential of biogas technology, they must be adapted to local conditions (e.g. high altitudes) requiring cooperation between academia and suppliers. In addition, policies to increase overall investment, through public-private partnerships, require to be developed as well as regulations allowing utilities to export excess energy to the grid or enforcing energy recovery. Last but not least, including capacity building on biogas technology – design, operation and maintenance.

[1] Copeland & Carter (2017): Energy-Water Nexus: The Water Sector’s Energy Use. In: Congressional Research Service.
[2] International Energy Agency, 2016: Water Energy Nexus. Excerpt from the World Energy Outlook 2016.
[3] Project for the Modernization and Strengthening of the Water and Sanitation Sector, on behalf of the German Federal Ministry of Economic Cooperation and Development (BMZ).

In the years and decades ahead, water and wastewater utilities can take many different actions to reduce greenhouse gas emissions. But what if they don’t? This is not a pessimistic question, but a very important one. Modelling a future with no mitigation actions – business as usual – is an important part of ensuring that actions happen.

That idea is the basis of WaCCliM’s new approach to understanding business-as-usual futures, the Methodology for Establishing Baseline Scenarios in the Urban Water Sector with ECAM.

The approach builds on the Energy Performance and Carbon Emissions Assessment and Monitoring (ECAM) tool, a first-of-its-kind online tool that allows water and wastewater utilities to take a holistic approach to reducing energy use and greenhouse gas emissions throughout the urban water cycle. ECAM allows utilities to enter their existing data into the tool and model actions they are considering to estimate the benefits of mitigation. The new baseline methodology goes a step further by identifying how emissions would evolve over time if current management and practices were to continue.

As water flows through an urban water cycle to meet the needs of residents and industry, greenhouse gases are produced indirectly through energy consumption, and often released directly from untreated or poorly treated wastewater. Modelling the unchecked growth of these emissions allows utilities to reveal the benefits of investing in mitigation – which they can do by getting more energy efficient, stopping water losses, better managing wastewater and sludge, or extracting and using biogas, among other possibilities.

Baseline scenarios are far from simple models; projecting past developments into the future requires many parameters and the best available data. Scenarios are based on the physical and biochemical characteristics of the emission pathways in the urban water cycle, with key parameters affected by socio-economic, technological and climatic forces, ranging from the numbers of people expected to move to cities to the composition of their diets. For rapidly growing cities in countries with developing economies, the only certainty with these parameters is that they will not stay static in the years ahead.

Yet it is possible to project them. They can be based on the trends derived from international and national databases, journal publications, reports and policy documents – including the reports and models of the Intergovernmental Panel on Climate Change (IPCC), which WaCCliM’s methodology takes as a basis.

There are four steps to the methodology. The first step involves defining the boundaries of the specific urban water cycle to be considered, and the time horizon over which it will be modelled. In the second step, the key parameters and driving factors of the emission trajectory are determined, taking national and global trends into account. The third step is data collection and projection, and for this WaCCliM has developed a custom Excel-based tool, Project ECAM Inputs for GHG Emissions (PEIGE). This generates a projection of business-as-usual conditions in future years that, in the fourth step, can be entered into ECAM’s freely available online interface to compare with alternative scenarios.

The power of this methodology is evident in two initial case studies published by WaCCliM. In Madaba, Jordan, WaCCliM modelled the possible trajectory of the utility Miyahuna’s greenhouse gas emissions under business as usual all the way to 2040. These will be critical years, with population growth, economic development and an influx of refugees widening the gap between water supply and demand in the dry region. The scenarios showed that the direct and indirect greenhouse gases emitted by the utility could increase from around 40,000 tons carbon dioxide equivalent (CO2e) in 2016 to nearly 110,000 in 2040, if the utility were to continue with no changes to its operations.

In San Francisco del Rincón in north-central Mexico, unsustainable abstraction, high water losses and inadequate wastewater treatment challenge the two utilities Sistema de Agua Potable y Alcantarillado de San Francisco (SAPAF) and Sistema Intermunicipal para los Servicios de Tratamiento y Disposición de Aguas Residuales para los Municipios del Rincón (SITRATA). WaCCliM also modelled the trajectory of these utilities’ business-as-usual emissions to 2040. The scenarios showed that emissions from the water supply system might increase by up to 58%, while emissions from the wastewater system could dip by 8% thanks to a gradually expanding treatment area.

Neither in Madaba nor in San Francisco del Rincón, however, did business proceed as usual. Among other measures, the Jordanian utility has upgraded pumps to more efficient models, already achieving 1,000 tons CO2e mitigation per year despite its fast-growing service area. The Mexican utilities, instead of expanding wastewater treatment gradually, have acted much faster to extend the system from 48% of the city to 80%, achieving mitigation of 2,500 tons CO2e per year.

The effects of actions like these need to be measured against something – and the business-as-usual scenarios are that something. The methodology is an important step towards estimating the reduction of utilities’ carbon footprints, and a strong technical component for further implementation of climate policies, right up to regional and national scales.

As global temperatures rise, it is the water cycle that is changing most dramatically, most unpredictably, and with some of the greatest consequences for people everywhere. Climate change is disrupting water availability and quality, amplifying floods and storms, and increasing the frequency of droughts. For water-sector decision makers, all of these impacts add up to a fundamental disruption: decisions that were once based on historical data are now afloat in uncertainties about the climate of the future.

At the same time, the water sector is, itself, a place to take on the drivers of climate change. Water and wastewater management are energy intensive processes theat cause significant greenhouse gas emissions whenever fossil energy sources are used. In addition, processing wastewater can be a source of methan and nitrous oxide.

Municipal systems, global commitments

Strong mitigation potential lies in urban water and wastewater systems, whose energy consumption, mostly driven by fossil fuels, makes up as much as 40% of municipal energy use in some cities. In developing and emerging countries, water and wastewater utilities often rely on inefficient pumps, leaky distribution lines and dated treatment technologies. They emit carbon dioxide from their energy use, and even more potent greenhouse gases – methane and nitrous oxide – from the breakdown of untreated or poorly treated sewage. Since 2014, the project Water and Wastewater Companies for Climate Mitigation (WaCCliM) has been working with selected countries and utilities to prove that in the urban water sector, climate mitigation action can be achieved alongside, and in harmony with, climate-resilient sustainable development.

WaCCliM’s experience has shown that the flow of water into, through and out of cities connects some of the largest commitments of developing and emerging countries. Among these, two stand largest: the Nationally Determined Contributions (NDCs) that governments have pledged in order to reach the climate targets of the Paris Agreement; and the Sustainable Development Goals (SDGs) that they are striving to achieve by 2030.

Clean water and sanitation command their own SDG, Goal 6, but in truth water runs through nearly all of the goals, and unites them with success or failure in climate action. Even in a stable climate, countries would be facing an enormous challenge just to reach Goal 6 – availability and sustainable management of water and sanitation for all. Billions of people still live without safe water, sanitation or both, and the effects undermine other goals like health, equality and the vision of sustainable cities. Now the uncertainties of the climate require thinking even harder about water insecurity, including in cities; about which people have as much water as they need without having more than they can manage, about how clean that water will be under all possible conditions, and about how to generate the energy that will get it there.

A climate-smart roadmap

WaCCliM’s Roadmap to a Low-Carbon Urban Water Utility, a tool for water and wastewater utilities with mitigation goals. © GIZ

The NDCs that countries have submitted reveal an awareness of just how central water is to climate adaptation. According to a Global Water Partnership analysis of 80 NDCs, investing in water infrastructure, institutions or governance is a key priority in 89% of the surveyed countries, and practically all countries indicate that some kind of water action is necessary for adaptation. Far fewer NDCs, however, mention the substantial opportunities to reduce greenhouse gas emissions found in the urban water and wastewater sector. It’s here that WaCCliM is guiding countries to mitigation opportunities, starting at the utility level.

The Project has introduced a roadmap of systematic steps and measures towards low-carbon water and wastewater utilities that can also plan for climate risks and improve their services to better support sustainable development. Helping utilities on this path is the project’s Energy Performance and Carbon Emissions Assessment and Monitoring Tool (ECAM), which any utility can use to assess its emissions and pinpoint opportunities to use less energy – or even generate its own energy.

From the utility up

WaCCliM has piloted mitigation solutions, ranging from energy-efficient pumps to technologies for generating power with wastewater biodigesters, with utilities in Jordan, Mexico, Peru and Thailand. The measures prioritised in these pilots have achieved total mitigation equivalent to 10,000 tons of carbon dioxide – or planting 50,000 trees – per year. WaCCliM is also introducing adaptation thinking by helping the pilot utilities develop climate risk plans, advising utility personnel on ways to build water system resilience to the risks identified, reducing water losses and recycling treated wastewater. The toolbox of both mitigation and adaptation planning measures will be available to utilities everywhere on the knowledge platform Climate Smart Water.

Water metering in Moroleón, Mexico. © GIZ/Maurice Ressel

Through these tools WaCCliM´s approach can substantially help meet NDCs across developing and emerging countries, and by building climate-smart urban water systems, it can help achieve the SDGs, too. This is a big vision, and it has to be achieved on a local, national and global scale. So while WaCCliM works with national and international partners to enable local action, it does this with a larger transformation in mind. The water and wastewater utilities using WaCCliM tools to pioneer greenhouse gas benchmarking and climate-smart planning are becoming national sector leaders, and they are providing evidence for an increased consideration of water as a sector for combined mitigation and adaptation action in the next round of NDCs. As that happens, they will also be poised to make a significant contribution to the sustainable development agenda.


[1] UN Water (2019): World Water Development Report 2019

The transition to low-carbon urban water utilities is an innovative idea, currently embraced only by a few forward-thinking utilities. Early adopters of the WaCCliM Roadmap to a Low-Carbon Urban Water Utility are well positioned for an uncertain water-climate future. This roadmap is directed at urban water utility managers in charge of planning future actions, as well as at the stakeholders who will support the utility’s action plans.

“The Roadmap to a Low-Carbon Urban Water Utility, a legacy from the WaCCliM project, builds on the experiences gained during the implementation of the project. It will support water utility managers around the world in their efforts to improve performance and achieve carbon neutrality of their utilities while raising the awareness of policy-makers to the substantial contributions the water sector can provide in meeting greenhouse-gas reduction targets. Local action is needed to support global targets!”

Thomas Stratenwerth, Head of Division – General, European and International Water Management Issues
Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany


The Roadmap to a Low-Carbon Urban Water Utility presents water professionals with an approach to address their most pressing challenges, while reducing carbon emissions through measures that either have a return on investment through energy or water savings, or that correspond to planned investments as part of the asset management plan to maintain or improve their services. Utilities adopting this approach are contributing to a carbon-neutral future, by instigating a change of mind-set, not only in urban water management but also by inspiring all other urban services through sharing the risks and the urgency to act to avoid aggravated impacts of climate change, from which water utilities are among the first victims: water scarcity, flooding and deteriorated water quality.

Why a roadmap and for whom?

The transition to low-carbon urban water utilities is an innovative idea, currently embraced only by a few forward-thinking utilities. This roadmap is directed at urban water utility managers in charge of planning future actions, as well as at the stakeholders who will support the utility’s action plans. Since only a few ‘early adopter’ utilities have embarked on a low-carbon transition, this roadmap intends to support other utilities in understanding and championing the need for contributing to a carbon-neutral future, and to guide them through a process of change. This roadmap can be applied to all utilities worldwide, but was specifically developed with utilities in emerging economies in mind, because the service performance and data management challenges are often prominent in their operations and future planning.

Setting a path for utilities to transition to low-carbon

The Water and Wastewater Companies for Climate Mitigation (WaCCliM) project supports potable water and wastewater utilities –also referred to as urban water utilities – with the implementation of measures that enhance their service performance and lower their carbon emissions. The project is a global initiative, with the overarching goal to transition to a carbon-neutral urban water sector. The approach laid out in this document was specifically developed with water utilities in emerging economies in mind within the context of the WaCCliM project, but it can serve utilities anywhere as climate change is a global problem. It targets reducing the water, energy and carbon footprints of urban water utilities through an iterative five-step process which may be used by utilities to find their own path to a low-carbon future. The roadmap is intended to guide urban water utility managers through these steps and leads to resources hosted on the Knowledge Platform ‘Climate Smart Water’, which follows the same structure as this roadmap.

The Roadmap to a Low-Carbon Urban Water Utility is available in English, Spanish and Thai.