Baltic Deal

Primary purpose

Active buffer zone June 2011. Photo: Frank Bondgaard Knowledge Centre for Agriculture. Denmark

Phytoremediation is a biological method for remediation of soil and ground water by using plants. By planting trees such as willows or poplars along streams it is likely to achieve a significant nitrogen removal in drainage water, while the biomass could be exploited for energy purposes. This allows better use of constructed wetlands while allowing for increased biodiversity.

Description

Phytoremediation occurs when the plants change the chemical, physical and biological conditions in the root zone, so substances are maintained or removed from the system. For nitrogen in particular, a significant removal occurs by denitrification, where nitrogen disappears in the form of gaseous nitrogen. The denitrification process increases significantly in the rhizosphere.

Proven effect

The effect of phytoremediation has not been elucidated under Danish conditions, but results are available from studies by the University of Iowa and show a 99 per cent reduction (from 150 to 2 mg/l) of nitrate nitrogen admitted horizontally from the surrounding area (Ostergaard 2009).

Assuming that an area with willow or poplar with water pouring from an adjacent area of 5 ha and assuming a removal of 90 per cent, this would mean an average removal of 270 kg N for 5 ha (average figures). 

Emphasis is made to the fact that the assessment originates from American studies, and an anticipated removal of many kg of nitrogen requires substantial increases in quantities of nitrogen to the system. 

Due to the limited knowledge, no effects or increased costs to this initiative have been stated. In the years to come, measurements of the effect of the project in question are likely to be made in Denmark.

Active bufferzone in Denmark 2011 with alder trees (Alnus incana and   Alnus glutinosa) and reed grass  (Phalaris arundinacea).

Drawing by Benjamin Christen. Institut for Jordbrugsproduktion og Miljø. Forskningscenter Foulum. Denmark

 Drainage dicch         Grass                  Grey and red eldertrees 

Drawing by Benjamin Christen. Institut for Jordbrugsproduktion og Miljø. Forskningscenter Foulum. Denmark

Drawing by Benjamin Christen. Institut for Jordbrugsproduktion og Miljø. Forskningscenter Foulum. Denmark

Original authors

Ph.D. student Benjamin Christen. Department of Agroecology and Environment. Research Centre Foulum. Denmark

Flemming Gertz. Knowledge Centre for Agriculture. Special Adviser. Plan & Invironment. Denmark

Hans Spelling Østergaard. Knowledge Centre for Agriculture. Special knowledge of plant production. Denmark

Camilla Lemming. Knowledge Centre for Agriculture. Special knowledge of plant production. Denmark.

 Funded by

 The European Fund for Rural Development

Ministry of Food, Agriculture and Fisheries in Denmark