This study evaluated the potential impacts of using waste-water heat to supply district heating systems and applied it to the situation in Serbia. The researchers say that widespread use of this approach could improve efficiency and reduce carbon dioxide emissions, and that the methodology could be applied elsewhere.
Global urban energy use is responsible for 70% of greenhouse gas emissions, with heating and cooling making up the majority of this energy demand. The European Green Deal recognises the importance of energy transition in heating and cooling through its Climate Target Plan and Fit for 55 package1.
Serbia has district-heating systems in 57 towns, supplying 44% of the country’s urban households. However, 99.5% of the energy for these comes from fossil fuels, with the remainder from combustion of biomass. Heat from sewage wastewater can provide a renewable energy source which is largely unused at the global level. This energy can be captured through heat pumps at waste-water treatment plants providing a relatively consistent supply. This study aimed to assess the technical potential for using energy from wastewater to supply district-heating systems, with particular reference to cities planning the construction of treatment plants.
The researchers used key performance indicators to assess the state of district-heating systems in Serbia in 2017, regarding energy sources, energy performance and carbon emissions. They then evaluated the potential for heat-energy capture based on the waste-water treatment plant in the city of Šabac, the newest in the country, which began operating in 2016. Finally, they projected the effects on the key performance indicators of supplying energy from wastewater to every district-heating system in the country.
The researchers report that most district-heating systems in Serbia (75%) were powered by natural gas imported from Russia, with some (14%) powered by oil mostly derived from imports and others (11%) from locally produced coal. They calculate the overall contribution of renewable energy as 0.5% (from limited use of biomass combustion) and the energy-import dependency as 72%. They provide a figure for the primary energy factor – how much energy was required at source to provide a unit of usable heat energy to the Serbian consumer – of 1.52. They also calculate the carbon dioxide (CO2) emission coefficient – the amount of CO2 emitted in producing a unit of usable heat energy – as 328.3 kilogrammes per megawatt hour (kg/MWh). The researchers say that the Šabac treatment plant has the potential to supply 20 160 MWh of heat energy through the whole heating season – the equivalent of 380 kilowatt hours per inhabitant served by the plant.
Applying these figures to a scenario in which all district-heating systems are supplied by energy from waste-water treatment plants, the researchers report that this would improve results for every key performance indicator. They say that the share of renewables would rise to 11% and the energy import dependency would decrease to 65%. They report a projected reduction in the primary energy factor to 1.47 and a 6.5% fall in carbon dioxide emissions to 307 kg/MWh. They add that when production, transport, and energy conversion are considered this could produce savings of 1 229.8 terajoules (approximately 340 000 MWh) – nearly 5% of Serbian district-heating energy consumption.
The researchers say that this study provides a widely applicable model for evaluating the technical potential of using renewable energy from waste-water treatment to supply district-heating systems. They argue that the potential benefits of deploying such systems in Serbia are significant and that this should be considered in planning for future treatment plants in the country. They highlight the positive impacts on import dependency and energy-source diversification as well as energy savings and CO2 emission reductions. They argue that this approach could be an important element in transitioning to sustainable, low-carbon energy systems.
- https://energy.ec.europa.eu/topics/energy-efficiency/heating-and-cooling_en [Accessed 24/05/2022]
Živković, M. and Ivezić, D. (2022) Utilizing sewage wastewater heat in district heating systems in Serbia: effects on sustainability. Clean Technologies and Environmental Policy 24: 579–593.
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“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.
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The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.
- Publication date
- 23 August 2022
- Directorate-General for Environment