Healthy Soil for Urban Agriculture through Nutrient and Carbon Circularity

Project Information

NUTRISOIL

Grant agreement ID: 101138151

DOI

10.3030/101138151

Project closed

EC signature date 19 October 2023

Start date 1 January 2024

End date 30 June 2025

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

UNIVERSITAT AUTONOMA DE BARCELONA
Spain

Periodic Reporting for period 1 - NUTRISOIL (Healthy Soil for Urban Agriculture through Nutrient and Carbon Circularity)

Reporting period: 2024-01-01 to 2025-06-30

Summary of the context and overall objectives of the project

Many policies promote urban and peri-urban agriculture (UA) through nutrient circularity to boost food autonomy, reduce food losses, and lower environmental impacts from transport, fertilizer production, and waste management. Yet, most EU cities still have low local crop production. Although cities generate large volumes of nutrient-rich waste, nutrient recovery via composting and wastewater treatment to replace mineral fertilizers in UA remains limited.
What hinders nutrient circularity in UA, and how can these obstacles be overcome? A key issue is the variability and quality of recovered nutrients. However, a more fundamental problem is the degraded state of urban and peri-urban agricultural soils. Adding nutrients to carbon-deficient soils is counterproductive, leading to poor root development, higher drought sensitivity, and reduced yields.
The solution lies within the cities themselves. Urban residues often contain decomposable organic carbon that can enhance soil microbiota, counteract acidification, and improve soil quality and nutrient cycling. The path to sustainable UA requires preserving and increasing soil organic matter (OM), while enhancing nutrient recovery locally—achievable through resource circularity inside the city.
NUTRISOIL aims to identify and resolve these soil-related challenges to sustainably implement UA by pursuing two main objectives:
A technical objective to test soil regeneration and fertilizing techniques combining recovered organic matter from pruning residues with nutrients from compost and wastewater treatment. This includes field experiments, analytical measurements, and environmental assessments. A social objective to engage stakeholders at both practitioner and policymaker levels through two workshops, fostering knowledge exchange among farmers, composting and wastewater facilities, waste regulation authorities, local crop commercialization agents, bio-based fertilizer regulators, and coordinating bodies involved in the urban nutrient cycle—from waste to food.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

NUTRISOIL advanced soil regeneration through urban carbon and nutrient circularity, involving stakeholders from industry, governance, management, and science. This collaboration resulted in several deliverables, including a policy brief.
Understanding Nutrient/Carbon Cycling in Urban Agriculture (UA): A systematic assessment of nutrient cycling was conducted in Barcelona and across European cities, resulting in a comprehensive database detailing UA practices, waste management, fertilization, soil preservation, and stakeholder engagement. Stakeholders were categorized into urban community, waste management, soil management, and agriculture, facilitating targeted workshop engagement.
Experimental Field Work: Various soil regeneration and fertilizing techniques using recovered organic matter and nutrients were tested in urban agricultural fields. Nutrient balances and agronomic guidelines were produced, supporting successful crop yields and environmental sustainability.
Environmental Impact Assessment: Emission factors for greenhouse gases were measured using static chambers and gas analyzers. Soil water infiltration and nutrient balances were assessed to understand environmental trade-offs. Life Cycle Assessments (LCA) integrated experimental data with urban metabolism studies, comparing the benefits and impacts of recovered organic matter versus mineral fertilizers. Results informed stakeholder workshops and supported two pending scientific articles.
Stakeholder Engagement and Action: Two practitioner workshops engaged over 70 participants from local and EU-wide levels, fostering dialogue between farmers, waste managers, municipal representatives, and policymakers. Key findings highlighted regulatory barriers, soil contamination issues, and the need for improved governance and collaboration. Innovative solutions such as organic waste reclassification, improved composting, and farmer incentives were proposed.
The workshops led to the policy brief Leveraging Biowaste to Revitalise Urban Agriculture, summarizing project insights and recommendations for promoting circular nutrient management in European cities.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

NUTRISOIL advanced the state of the art by linking waste recovery and sustainable urban agriculture through experimentation, analysis, and stakeholder engagement, delivering three key innovations:

Technical Innovation in Soil Regeneration:
The project showed combining RCW from pruning with recovered nutrients (compost, struvite, Labinor) regenerates peri-urban soils effectively. Field trials with spinach and sweet potato revealed improved yields, over tenfold reductions in N2O emissions with RCW, better soil structure, increased water infiltration, and lower environmental impacts than conventional synthetic fertilization—confirmed by life cycle assessment (LCA).

Systems Perspective and Environmental Assessment:
Using urban metabolism and life cycle thinking, the project assessed trade-offs of resource recovery and soil amendments. Coordinated with ERC URBAG, it quantified avoided impacts of organic residue reuse (e.g. pruning waste versus incineration) and synthetic fertilizer replacement. These metrics support evidence-based planning and emphasize the systemic value of urban carbon and nutrient circularity.

Stakeholder Co-Production and Policy Transfer:
NUTRISOIL engaged farmers, waste managers, municipal planners, and EU policy experts through local and EU-wide workshops to identify barriers and co-create solutions. Key challenges include restrictive regulations on compost/digestate use, limited infrastructure linking biowaste to urban farms, and lack of incentives and secure land access for farmers. The policy brief, “Leveraging Biowaste to Revitalise Urban Agriculture,” offers actionable recommendations for integrating nutrient circularity into urban resilience and biodiversity policies.

Dissemination via EURESFO, the Resilient Cities Network, and Cities on the Frontline webinars raised awareness among European urban leaders and practitioners.

In sum, NUTRISOIL offers a comprehensive framework—grounded in experimentation, environmental assessment, and stakeholder dialogue—for scaling circular solutions that regenerate urban soils. It bridges urban biowaste management with sustainable food production and climate resilience, positioning UA as a key driver and beneficiary of circularity in cities.

figure of NUTRISOIL

graphical abstract of NUTRISOIL