trends and future of sustainable development - TransEco

(methodological, spatial and time-scales). The analytical calculation procedures used in this study aredescribed elsewhere (Fahd et al., 2010, in press).4. ResultsThe final performance indicators for the agricultural and industrial steps of the first case study areprovided in Table 1. It includes results from all the different methods applied within the SUMMAframework to a low input Brassica cropping. Analogous assessments were made also for high inputcropping (data not shown). Indicators in the Table are intensity indicators, i.e. indicators per functionalunit of product generated, with products measured according to their energy content, mass andeconomic value, when applicable. As always in the SUMMA procedure, the Table is divided into fourmain categories of indicators: Material Resource Depletion (abiotic material depletion and waterdepletion); Energy depletion (given as embodied energy use); demand for Environmental Support(emergy); Downstream Impacts (Global Warming Potential, Acidification Potential, EutrophicationPotential). Within the category of Emergy Indicators, the Emergy Yield Ratio, the EnvironmentalLoading Ratio, the Emergy Sustainability Index and the % Renewable Emergy are also calculated.Regarding the material resource depletion, the highest values, in terms of both abiotic material andwater use, were calculated for Brassica oil extraction and biodiesel production. In a like manner, therequirements causing higher energy resource depletion were found for Brassica oil (0.29 g oil equiv.)and for biodiesel (0.50 g) in comparison to only 0.07 g oil equivalent needed to make one g of seeds.Therefore, half a gram of oil is invested to generate 1 g of oil equivalent energy. This means that the netenergy delivered to society is only 50% of the total yield and that two hectares are needed in order tomake one “net hectare”. The energy return on the energy investment (EROI) ranges from 8.81:1 for seedsto 1.81:1 for biodiesel. Although the energy delivered is slightly higher than the energy invested, such aresult is largely inadequate to support the energy intensive production processes of our society,compared to the EROI of refined fossil fuels (in the range 5-6:1). Considering the demand forenvironmental support (Emergy Intensity), the transformity calculated for biodiesel (3.11E+05 seJ/J) is70% higher than for fossil diesel (1.81E+05 seJ/J, Brown et al., 2011, 879-887), indicating that biodieselis three times more demanding in terms of global biosphere support (environmental inputs, land, water,indirect factors, etc). Additionally, the EYR (total emergy exploited/emergy invested from outside) is anindicator of the ability of the process to make new resources available per unit of investment and thevalue found for biodiesel (1.14:1) is very low compared to fossil fuels (presently around 10:1). This meansthat fossil fuels provide to the economy a net contribution of resources that is much higher than thatsupplied by bioenergy processes. Moreover, emissions of CO 2 and other greenhouse gases are relativelylow (0.13 g CO 2 per g dry seed) in the seeds production, whilst in the oil extraction and biodieselproduction emissions grow to 0.63 and 1.24 g CO 2 per gram of oil and biodiesel, respectively, as aconsequence of the high direct and indirect demand for energy, without considering the emissionsreleased by the use of the generated fuel.Data calculated in terms of energetic and economic evaluations are reported respectively in Table 2and Table 3. In general, the energy content of biomass or biofuel does not indicate the net energy that isactually available to the larger economic system, because there is an investment of energy embodied inthe production factors (fertilizers, machinery, fuel) that needs to be subtracted. Besides the Energy48