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).