1. Department of Food and Resource Economics
What is the cost- effectiveness of filters? and which data are required for the calculation?
Associated Professor Brian H. Jacobsen
Department of Food and Resource Economics (IFRO)
Workshop on wetlands to reduce N-loss

2. Catalogue of measures from 2014
Surface Flow Constructed mini-Wetlands (SFCW)
Sub-Surface Flow Constructed Wetlands (SSFCW)
Controlled Drainage (CD)
Traditional Wetlands (TW)

3. Wetlands - effects and potential
Potentieal area (ha)
Sandy
(kg N/ha/yr)
Clay
Average
(kg P/ha/yr)
SFCW ?
4 – 18 %
30 – 40%
5 - 46 %
SSFCW
9 - 26 %
9 – 26 CD
6 - 30 TW
10.000
80 – 90
0,5 – 1,5
Source: Eriksen et al. (2014)
Note: For TW the area is the actual wetland area

4. Wetlands – Costs (Norsminde analysis)
SFCW
SSFCW
Total costs (DKK) (100 ha)
Basic costs per project (DKK)
40.000
Investment per ha (DKK/year)
2.100
3.600
New filters (DKK/year)
10.000
Share of area as wetland ( %)
(set a side) 1
0,6
Effect rootzone (kg N/ha)
6 -18
9 - 26

5. Wetlands – Costs (DKK/ kg N)
Effect (kg N per ha)
Lifespan (years)
Area (ha)
SFCW
SSFCW 5
156 38
357
107 10 96 23
198 59 30 56 14 93 26 50 48 12 72 19 70 45 11 63 17
100 42 15
Note: Most fields are below 10 ha

6. Measures in Food and Agricultural Package from 2015
DKK/kg N
Catch crops direct cost
(300 DKK per ha and 9,6 kg N/ha) 31
Catch crops with compensation
(700 DKK per ha and 9,6 kg N/ha) 73
Wetlands (90 kg N/ha) 52
Set a side (low areas) (40 kg N/ha) 87
Mini wetlands (9 kg N/ha)
( kr./ha)
(1.000 projects -> 900 tons N/yr) 55

7. Conclusions
The cost effectiveness is related to :
- The N-efficiency of the project
- The cost of the project
- The area it has an effect on (field)
- Lifespan of the project
With large area and effect the costs per kg N for wetlands are low
The sub-surface wetlands have a higher cost per kg N
Effects on e.g. P improves cost-efficiency
Farmers’ interest in wetlands is high

8. Institut for Fødevare- og Ressourceøkonomi
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9. References
Jacobsen B.H, Gachango FG (2013) Vurdering af omkostningseffektiviteten ved minivådområder med infiltrationsmatrice. Institut for Fødevare- og Ressourceøkonomi, Københavns Universitet, Frederiksberg
Gachange, F; Pedersen, S.M. and Kjærgaard, C. (2015). Cost-Effectiveness Analysis of Surface Flow Constructed Wetlands (SFCW) for Nutrient Reduction in Drainage Discharge from Agricultural Fields in Denmark. Environmental Management (2015) 56: doi: /s y
Gachange, F. and Jacobsen, B.H. (2017). How to introduce new technologies to reduce nutrient losses: a case of Danish agricultural wetlands. Water Policy. Vol. ? pp
Ørum, J.E.; Kjærsgaard, C. and Thomsen, I. (2017). Implementering af virkemidler i Norsminde Fjord. Notat. IFRO. Københavns Universitet. (not published yet)