D1.2 - Nutrient imbalance analysis (summary)

This deliverable (D) 1.2 was developed under Work Package 1 (WP1) of the WalNUT Project, led by CARTIF in collaboration with several European research institutions, including APCA, CETAQUA, UGent, NTUA, SDU, UCPH, UNITO, and ITACYL. The WalNUT project, funded under Horizon 2020, focuses on closing waste water nutrient cycles by assessing nitrogen (N) and phosphorus (P) availability and recovery potential in Europe.

The D1.2 builds on D1.1 – Nutrient Flow Analysis and Transfer Model, further assessing Gross Nutrient Balance (GNB) across EU countries to understand nutrient surpluses and deficits. It evaluates regional nutrient flows, stocks, and replacement potential using waste water-derived nutrients to reduce dependency on inorganic fertilisers. The study aims to improve nutrient management and enhance circular economy strategies in agriculture.

The GNB analysis shows that while nitrogen and phosphorus surpluses have declined inrecent years, nutrient imbalances remain a significant environmental challenge in theEU. Some countries have excessive nitrogen surpluses, such as Belgium (139.69 kg N/ha),the Netherlands (177.88 kg N/ha), and Cyprus (191.06 kg N/ha), while others, like Bulgaria,Germany, and Hungary, exhibit phosphorus deficits. The country-by-country nutrient replacement potential analysis showed that urban and industrial waste water treatmentplants (WWTPs) could serve as secondary nutrient sources, reducing reliance onchemical fertilisers.

Key Country-Specific Results

Denmark: The highest agricultural demand is in Syddanmark and Midtjylland,but only 3% of inorganic nitrogen demand and 13% of phosphorus demand can be replaced by WWTP-derived nutrients.
Spain: Cataluña and Madrid show the highest nutrient replacement potential,with 41% of nitrogen and 29% of phosphorus demand met through waste water-derived nutrients, while Castilla y León faces major supply-demand gaps.
Belgium: The Brussels region has high nutrient releases relative to demand, with8% nitrogen and 55% phosphorus replacement potential, highlighting wastewater as a key phosphorus source.
France: Île-de-France and Provence-Alpes-Côte d'Azur have high nutrient surpluses, with 53% nitrogen and 66% phosphorus replacement rates, showing strong recovery potential.
Greece: Attica (Athens region) has an excessive phosphorus surplus, covering376% of regional P demand, while other regions face nutrient deficits requiring imports.
Hungary: Budapest WWTPs could theoretically supply 323% of nitrogen demand,yet regional discrepancies mean nutrient reallocation is necessary for balance.
Italy: Lombardy and Lazio have the highest potential for nutrient reuse, with 24%nitrogen and 37% phosphorus replacement rates, while Southern Italy faces major deficits.
Portugal: Lisbon and Madeira have an overabundance of recovered nutrients,covering 333% of nitrogen and 216% of phosphorus demand, but Alentejo and other rural regions struggle with shortages.

Conclusions and Next Steps

This study highlights the growing potential of waste water-derived fertilisers to reduce environmental nutrient loads and improve agricultural sustainability. However, regional discrepancies in nutrient distribution demand case-by-case management strategies toensure effective nutrient reallocation. Future work in the WalNUT project will focus on regional policy recommendations, improved nutrient recovery technologies, and logistical solutions to optimise bio-based fertiliser use and support a circular nutrien teconomy.

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