Energy analysis of three energy crops in Greece
Keywords:rape seed, sunflower, sweet sorghum, energy analysis, net energy, energy efficiency coefficient
To assess the potential of energy crops to provide a stock material for biofuel production three crops (rapeseed, sunflower and sweet sorghum) were studied in field experiments in Thessaly, Central Greece in 2007 and 2008. The cropping activities were recorded. Energy analysis was carried out to assess benefits from the crops. Power requirements and energy consumption during field operations were measured directly using instrumented tractors. Literature data was used for the energy sequestered to the inputs of the system (indirect energy). Energy budgets were produced taking into account as output either the seed or including the stalks for the two oil seed crops. The results showed that in all cases positive energy balances were achieved. Analysis of the inputs showed that energy for fertilizer was the most important for the rain fed rapeseed but irrigation for sunflower and sweet sorghum. Pumping depth of the irrigation water had a high impact on the energy inputs of the irrigated crops. The overall results gave maximum energy efficiency coefficients of 4.62 for rapeseed without the stalks and 10.68 with stalks, of 2.89 for sunflower without the stalks and 6.16 with stalks and 8.92 for sweet sorghum. An analysis of data from the literature was carried out to assess the effect of new technological developments to the energy sequestered to different inputs. Several developments are expected to improve energy efficiency coefficient, such as variable rate application of inputs, as well as properly designed crop rotations and use of cover crops.
Keywords: rape seed, sunflower, sweet sorghum, energy analysis, net energy, energy efficiency coefficient