PROJECT DESCRIPTION
BACKGROUND
Diffuse pollution affects 90% of river basin districts, 50% of surface water bodies and 33% of groundwater bodies across the EU. Manure nutrients, especially nitrogen and phosphorous, are among the main sources of pollution, especially in high-density farming areas. Agriculture and livestock are responsible for over 50% of the total nitrogen discharged into surface waters. This contributes to eutrophication, a key threat to the good ecological status of EU surface waters under the Water Framework Directive. The Nitrates Directive was introduced to protect water against nitrate pollution from agricultural sources. To this end, several technologies have been developed to solve the problem of excess nitrogen and phosphorous in manure, but these often require large amounts of energy and chemicals. Duckweed (Lemnaceae) is a small floating macrophyte with a high capacity for removing dissolved nutrients from water, especially nitrogen and phosphorous. It produces biomass with high nutritional value. Duckweed has been used for the uptake of nutrients from non-agricultural waste, but it has yet to be applied to animal manure on an industrial scale in the EU. Laboratory-scale tests have shown promising results, and an industrial-scale demonstration is now needed, particularly as a complement to anaerobic digestion.
OBJECTIVES
The main objective of the LIFE LEMNA project was to demonstrate the feasibility of an innovative nitrogen and phosphorous recovery technology, to improve nutrient management and reduce the environmental impact of animal farming. This biological, energy-efficient system would involve the sustainable treatment of anaerobically digested manure through a duckweed production system. Duckweed biomass would be processed to obtain new bio-based products for local consumption, mainly bio-fertilisers and animal feed. It would also feed an existing biogas plant in the same location, which will allow the system to run 100% on green energy. The project planned to test the new technology in a 250 m2 duckweed production prototype with a treatment capacity of 3 m3/day, which would be installed and operated over a period of 21 months on a pig farm in the Spanish region of Catalonia (province of Lerida).
Specifically, the project aimed to:
- Reduce manure nutrient pollution of water bodies in farming areas by implementing an innovative and resource-efficient duckweed-based technology to help farmers achieve integrated nutrient management;
- Demonstrate the efficiency and sustainability of the technology to achieve high rates of nutrient recovery, including nitrogen and phosphorous, in comparison with existing technologies; and
- Improve resource efficiency and close mineral cycles in animal farming systems by integrating duckweed production and bio-based related products (nutrients rich bio-fertilisers and high quality animal feed) within a low-input value chain inspired by the circular economy concept.
RESULTS
The LIFE LEMNA project established collection of 48 strains of duckweed from 40 populations around the Iberian Peninsula, covering the three European bioclimatic regions. This collection will be maintained after the end of the project by means of a long-term preservation protocol developed by the project. The beneficiaries demonstrated the viability of growing duckweed using pig manure digestate as a cultivation media. The four duckweed strains with the highest tolerance to this media and more efficient in terms of biomass production and nutrient uptake were identified by trials carried out in the laboratory and at a pilot plant.
A 250 m2 prototype was built at PORGAPORCS farm in Catalonia, the Spanish region with the highest concentration of pig farms and consequently a high level of diffuse pollution in its water bodies. The scaled-up prototype operated for over a year during the project, treating pig manure using the duckweed technology. The nutrients uptake rates achieved were 54% for nitrogen, 45% for phosphorus and 71% for potassium, although nitrogen is fully depleted within the system. Duckweed performance in other European climates was also assessed in laboratory conditions. Based on the results, the project developed the ‘e-lemnatool’, which is available on the project website. This tool enables an easy feasibility assessment of the LIFE LEMNA system using basic data from any farm; and it was validated with 20 real cases.
The beneficiaries moreover validated the potential of duckweed as animal feed (dry biomass) and as fertiliser (liquid fraction). Carbon footprints of these bio-products are smaller than conventional products (6% less than inorganic fertilisers and 28% than soy protein). A Life Cycle Assessment demonstrated the good environmental performance of the LIFE LEMA system compared to current manure management and to alternative technologies to absorb or deplete nutrients.
The farm involved in the project (PORGAPORCS) is assessing the potential of installing a full scale plant in order to treat all the exceeding manure. However, before upscaling to industrial size, further research is needed. The project initiated discussions with policy-makers at regional level in order to address the policy barriers encountered and to include the project's technology on the list of techniques for manure management. The main barrier is the prohibition of using duckweed grown on digestate from pig slurry to feed animals due to hygienic restrictions.
Finally, the project has raised awareness in the region regarding the environmental problems linked to livestock farming. It has also increased knowledge about the EU programs and the population confidence on the positive impact of the EU projects.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
