Assessment of Different Doses of Sewage Sludge Application on Virginia Fanpetals Biomass Feedstock Production

The objective of this study was to determine the effect of increasing municipal sewage sludge doses on Sida hermaphrodita Rusby (Virginia fanpetals) yielding and bioenergy feedstock characteristics. In a six-year-lasting field experiment two methods of plantation establishment (by roots cuttings and nurse-in-tray plantlets) and three dates of biomass harvesting (autumn, winter and spring one) were additionally tested in climatic conditions of south-eastern Poland. Virginia fanpetals dry yields increased each year and exceeded 20 Mg ha(-1) in the second year of culture. Application of 40 Mg ha(-1) sludge DM resulted in obtaining the highest yield. Similarly the content, uptake and index of bioaccumulation of macronutrients contained in the sludge increased along with increasing its dose. Biomass was characterized by a favorable parameters: net calorific values were in the range of 16.2-16.7 MJ kg(-1). The highest energy value of biomass yield was obtained with root cuttings use for plantation establishment, especially in objects with high dose of sludge during autumn harvest. Both, winter and spring harvesting significantly reduced yields, while using root cuttings for plantation establishment gave better yields only during the first three years of plant vegetation, than biomass yields equalized with the ones obtained by plantlets planting.