Wastewater treatment is an essential public service that has a major impact on energy use in the urban water cycle, thus receiving increasing attention in context of the Water-Energy Nexus. Understanding the current energy use for wastewater is an essential step to design reliable policies promoting a more efficient use of resources. This paper develops a pan European estimation of electricity use for the treatment of wastewater, based on a dataset of wastewater treatment plants (WWTPs) across the continent. Prediction of electricity use has been performed using a statistical model that accounts for economies of scale. Different scenarios of improvements of energy use efficiency have been investigated to understand the possible reductions in electricity consumption at the continental scale. The overall WWTP electricity use in Europe (only plants with no less than 2000 population equivalent (PE) have been considered) was estimated at 24 747 GWh yr −1 , about the 0.8% of the electricity consumption in the EU-28. Small plants (less than 50 000 PE) represent almost 90% of the total number of plants, but process only 31% of the PE and require 42% of electricity use. Plants from mid to very large size (more than 50 000 PE), being only 10% of the plants, process about 70% of the PE with 58% of the total electricity use. If all plants that use more than the current average were shifted to the average value, the saving would be slightly more than 5500 GWh yr −1 . With highly stringent targets of efficiency improvement, saving of about 13 500 GWh yr −1 could be expected. Further considerations on the emerging role of WWTPs as energy and material producer are finally discussed.

Summary Phosphorus is an essential nutrient for all forms of life, which means that food cannot be produced without it. As the phosphate rock (concentrated source of phosphorus) is a non-renewable and finite resource, with no substitute, without more sustainable management of phosphorus its deposits could be depleted in a rather short period. In addition, much of phosphorus eventually ends up in environment, where it causes pollution. Hence, one could say that the lack of phosphorus and its inappropriate management could be a bottleneck for a sustainable food supply and agricultural development in general. Nevertheless, unlike some other challenges that modern agriculture has to face (for example, water and energy scarcity, climate changes etc) the problem of phosphorus limited availability and accessibility has been largely neglected until recently. This paper’s particular intention is to explain why phosphorus management is one of key issues for the sustainable food supply and agricultural development, which factors have to be considered when dealing with this topic and which technologies could be applied as potential solutions. One solution to become independent from the fossil deposits of phosphorus might be its extraction from wastewater, which could contribute significantly to overcome the looming phosphorus and growing environmental crisis.