Sewage sludge compost use in bioenergy production - a case study on the effects on Cynara cardunculus L energy crop.

Abstract As energy obtained from biomass is expected to significantly contribute to the future renewable energy pool, knowledge regarding energy crops management is crucial in order to maximize productivity while establishing positive environmental synergies. In this sense, the application of waste materials as organic amendments represents an interesting option for the growth of energy crops in Mediterranean regions. This is the first three-year trial (2008–2011) that assesses the effect of different sewage sludge compost treatments, applied as basal dressing, on the productivity the energy crop Cynara cardunculus L. (cynara). The experiment was conducted in Alicante (Southeastern Spain), testing four compost application rates: 0, 30, 50 and 70 t ha −1 . Cynara yields (dry basis) were higher in the 2010/11 comparatively with 2008/09 for aboveground biomass (2063 vs 1202 g m −2 ), seed yield (320 vs 153 g m −2 ), oil yield (81 vs 33 g m −2 ) and energy yield (37 vs 21 MJ m −2 ). Concerning fertilisation treatments, composted sludge exerted positive effects, mainly between 50 and 70 t ha −1 application rates, primarily improving the productivity of cynara: aboveground biomass (2195 g m −2 ) and energy (38 MJ m −2 ) yields of plants amended with 70 t ha −1 were 68% higher than control plants, while seeds (308 g m −2 ) and oil yields (103 g m −2 ) increased by 40%. Therefore, the use of SSC enhanced cynara's productivity (aboveground biomass and seeds yields primarily). The present research provides valuable data to growers and researchers interested in the maximization of environmental positive synergies (soil protection, waste reuse, bioenergy production), as a way to enhance the sustainability of Mediterranean agrosystems.