Marc Londo

Energy farming in Dutch desiccation abatement areas: yields and benefits compared to grass cultivation

Abstract Measures to combat desiccation of Dutch nature reserves often lead to the establishment of buffer areas around them, in which soils become moisture, and agricultural yields decrease. Cultivation of the flooding-tolerant energy crop willow may be an alternative in such areas. In this study, the performance of willow production is compared to that of grass for roughage. The effect of high groundwater tables on yields of both crops is estimated using the agro-hydrological model SWAP. Financial consequences are evaluated by calculating the biomass price that, for a farmer, makes willow equally competitive as grass. At groundwater table class (Gt) II, common in buffer areas, willow physical yield is ca. 15% lower than its optimum, but grass yield decreases by ca. 25%, making willow more competitive. This results in a 20% lower break-even willow price on Gt II than in a drier, optimal situation. A sensitivity analysis shows that most parameters with a strong influence on the break-even willow price have reasonably high certainty. An uncertain value with strong influence is the willow yield without hydrological constraints, which could not be estimated from practical data. Methodological limitations of the study, both in the financial comparison between willow and grass, and in the yield estimations, are also discussed.

Measurements on water containing dissolved and suspended matter from natural sediments

Abstract The presence of dissolved and suspended matter (DSM), originating from three different natural sediments, was measured as dry weight concentrations (DW), dissolved organic carbon concentrations (DOC) and enhanced concentrations of three chlorobenzenes. The latter were measured in a recently developed method, in which the water containing DSM is contaminated with the chemicals by air in an air-bridge system. This method appears to be suitable for measuring enhanced concentrations in suspension water of relatively volatile compounds. DW and DOC concentrations and enhanced concentrations vary considerably between the three sediments. Moreover, the results are not in parallel, i.e. enhanced concentrations cannot be predicted by DW or DOC of the suspension water. This implies that neither DW nor DOC give a good description of the influence of DSM on the sorption behaviour of chemicals in water.