How the Interreg project ReNu2Farm is supporting soil health and the circular economy

This case study was originally published by the Microbiology Society under the following link:

The Microbiology Society is undertaking a project entitled A Sustainable Future as part of our 75th Anniversary, which aims to highlight the Sustainable Development Goals (SDGs) to our members and empower them to use their research to evidence and impact the goals. Earlier this year, we put a call out to our members to submit case studies in the following three areas: antimicrobial resistance, soil health and the circular economy.

This case study is written by Dr Achim Schmalenberger, who is a Senior Lecturer and Course Director, and Lea Deinert who is a researcher at the University of Limerick, Ireland. They are both members of the Microbiology Society. It focuses on Soil Health; maintaining the health of our soils has gained increasing prominence in recent years. Soils are essential for the global food system and regulate water, carbon and nitrogen cycles but are put under pressure from population growth and climate change.


What are the challenges that this research/initiative addresses?

Our current practices in agriculture are heavily dependent on the use of synthetic fertilisers. This presents sustainability challenges, as the key components of these inorganic fertilisers are either mined in the case of phosphorus and potassium, or extracted from the atmosphere at high energy costs, in the case of nitrogen.

Rock phosphate is excavated commercially in a handful of locations across the globe. Some countries which hold a significant portion of global phosphate resources are located in conflict areas such as the Western Sahara, while others are expected to be exhausted within the next 30 years. Currently, agriculture in Europe is highly dependent on Moroccan mined rock phosphate, which is also associated with cadmium contamination, that can lead, in the long-term, to heavy metal pollution of soils and food products.

While nitrogen fertiliser can be synthetized from the atmosphere, this comes at the expense of fossil fuel consumption. Synthetic fertilisers have been demonstrated to negatively impact soil biota diversity and function and are therefore detrimental to soil health and sustainable farming practices. We therefore need alternative sources for nitrogen and phosphorus to support the circular economy and soil health. The European Interreg project ReNu2Farm is studying the use of recycling derived fertilisers (RDF) to substitute a portion of the current synthetic fertiliser usage. The use of RDF will support the circular economy and is hypothesised to improve soil health.

ReNu2Farm is a European interdisciplinary project that investigates:

  • The production of RDF
  • Their distribution in the North-West of Europe, where demand on nitrogen and phosphorus and their availability may vary greatly
  • Acceptance of RDF by farmers (Cork IT)
  • The environmental impact of RDF on the soil biota and soil health (University of Limerick & IT Carlow)
  • Their agronomic performance (Teagasc)


What findings and solutions were provided by this research/initiative?

For Irish agriculture, ReNu2Farm is investigating the performance of RDFs derived from sewage sludge and poultry litter ash, as well as struvites from municipal and industrial waste water in grasslands. Our findings, in pot trials and from the field experiments (shown in the image below) support the use of these RDFs as an economically viable replacement of synthetic fertilisers.

Grassland Field trial, Johnstown Castle, Ireland

Grassland Field trial, Johnstown Castle, Ireland

Likewise, current investigations on the biological safety of the RDFs indicate no hazardous or negative impact on the soil biota diversity. Several indicators for the microbiological mobilisation of phosphorus in soil were enhanced when RDFs ash and struvite were applied; when compared to the use of triple-superphosphate.

Interestingly, pot and microcosm trials simulating consecutive growing seasons of grasslands highlighted the benefit of RDF use. We found evidence of improved soil health, in the form of enhanced microbial activity and diversity in phosphorus mobilisation. We will validate these laboratory-based findings in our 2020 field trials.


How can this research/initiative support the transition to a more sustainable future?

The use of RDF to replace synthetic fertilisers has great potential to boost the circular economy by reusing key nutrients needed for food production. Currently, many nutrient-rich waste streams are disposed of in landfills. By reutilising these resources, we will support sustainable agricultural practice, as the more widespread use of RDF will ensure a sustained supply of nutrients.

Regional production of RDF will reduce the fertilizer’s transport carbon footprint when compared to overseas imports, and will alleviate Europe’s dependency on P supply from geopolitical impacted countries. Furthermore, the RDF fertilizers evaluated in this project will not damage soil biota. As a result, soil microbes can fulfil their ecosystem functions, including the cycling and mobilisation of nitrogen and phosphorus. Indeed, early evidence from our investigations indicate that the use of RDF is better for soil biota diversity and function than triple-superphosphate, thus RDF use has the potential to improve soil health. ReNu2Farm is working with stakeholders that produce RDF in Europe as well as with their potential customers i.e. farmers, in order to promote the use of RDF instead of synthetic fertilisers. ReNu2Farm is creating awareness of the availability of RDF and demonstrates the benefits of its use through the newly obtained scientific evidence.


What is the future for research and innovation in this area?

Further investigations into the long-term effects of RDFs are needed to convince stakeholders that the use of RDFs may be beneficial; not only for the circular economy, but also for agricultural output, as well as supporting soil health and therefore be a sustainable solution to the current challenges in agriculture across Europe. ReNu2Farm strives to further identify the effects of the application of RDF on agricultural output and soil biota diversity, and function in various scenarios of agriculture across the North-West of Europe, so that stakeholders will have the confidence to widely apply the tested RDFs in the future. The fertilizer industry will gain critical information on the economic value of their produced RDF, and whether farmers are accepting RDFs as a replacement for synthetic fertilisers like triple-superphosphate or are willing to implement RDFs into their fertilising scheme.



We would like to acknowledge the contributions from our Irish ReNu2Farm partners Niamh Power, representing Cork IT, Thomae Kakouli-Duarte representing IT Carlow and Patrick Forrestal representing Teagasc (Johnstown Castle).


About Irish ReNu2Farm partners

ReNu2Farm partners in Ireland are investigating consumer acceptance (Cork IT), the biological safety of the RDFs to the soil biota (IT Carlow), the effect of RDF on microbiological cycling of nitrogen and phosphorus (University of Limerick) and the agronomic performance and plant availability of nutrients (Teagasc). Further information on the overall project can be found on their website.

About the Authors

Dr Achim Schmalenberger is a Senior Lecturer and Course Director at the University of Limerick, Ireland and a member of the Microbiology Society. More information about his work is available here.

Lea Deinert is a researcher at the University of Limerick, Ireland and a member of the Microbiology Society. More information on her work is available here.

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