engleski

Sewage Sludge Management via Energy Crop Production

The use of sewage sludge in agriculture is regulated by strict rules and directives in both the EU and Croatia. Nevertheless, there is great potential for progress in the application of sewage sludge to soils in larger than specified quantities when applied to non-food crops. Indeed, the Regulation on the Management of Sewage Sludge from Wastewater Treatment Plants when Used in Agriculture (OG 38/2008) in Croatia stipulates that a maximum of 1.66 t/ha dry matter of sewage sludge may be applied to the soil per year. However, it is possible to use a larger amount of sludge in agriculture by cultivating energy crops that also phytoremediate the soil. This method of sewage sludge application could improve poorer quality soils that are not competitive in conventional food production. Namely, only on such soils, crops for energy production can be grown, in order to avoid undesirable competition between energy and food production. Taking into account Croatia's agro-climatic conditions and the obligation to grow energy crops on marginal soils, the rhizomatic grass Miscanthus x giganteus is the optimal solution. The aim of the project "Sewage Sludge Management via Energy Crop Production", funded by the Croatian Science Foundation, is to analyse the properties of soil and sewage sludge and to determine the effects of fertilising with sewage sludge on the yield and the energetic properties of Miscanthus biomass. The main objective of the research was to investigate the effects of the application of sewage sludge from the Zagreb WWTP in three different rates of application 1.66, 3.22 t/ha and 6.44 t/ha on soil properties and on the yield and quality of Miscanthus biomass in the two growing seasons. The analysis of the sewage sludge quality showed that the concentration of heavy metals was below the maximum permissible concentrations and that sludge was withouth pathogenic bacteria. According to organic matter and valuable nutrients content the sewage sludge can be classified as an organic soil improver. After the application of the largest amount of sewage sludge, the standard biomass yields were observed without a significant soil heavy metal accumulation and energetic properties of the Miscanthus biomass suitable for the process of direct combustion.

Sludge ; energy ; biomass ; Miscanthus ; application

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