SOSTENIBILITÀ COMPLESSIVA DI FILIERE AGRO-ENERGETICHE

Recent decision in European environmental policy to increase the share of renewable energy will lead to an increased demand also for energy by farm. The multiplicity and heterogeneity of biomass and of energy products is also reflected in different types of energy conversion processes and different technologies for energy generation. These activities represent an important diversification of the agricultural production, in certain cases and certain situations the economic performance foreseen are of great interest and significance. Actually, the most interesting agro-energy chains are anaerobic fermentation in order to produce the biogas and the thermochemical process of wood biomass to produce directly energy or others energy carriers (bio-oil, bio-char, syngas). Therefore, the sustainability of any agro-energy chains depends not only by technical -economic issues (those routinely investigated and verified): energy and environmental aspects (as happens more often) must be take in account. These two aspects are not easy to quantify and have been neglected. Only the parallel verification of the economic, energetic and environmental results (EEE) can fully clarify the sustainability of a chain of bio-energy. Thus, the possibility to have a model that calculates, in an analytical and uniform way, costs (inputs) and benefits (outputs) of each chain by defining the balances EEE, allows: - to identify those at greater sustainability - to compare objectively the various technical solutions available, providing valuable information on strategies for promotion of agro-energy. Although in recent years, the study of energy and environmental balance of the agro-energy chains has attracted growing interest, most studies refer to the production of biofuels (pure oil, biodiesel, bioethanol) and operative conditions different than Italian. From the practical point of view, the assessment of different energy and environmental aspects however, is much more difficult than technical-economic. Indeed, the failure to define a common methodology, plus the substantial gap (or, however, the strong heterogeneity) between the parameters used from time to time. Only recently, worldwide and in Europe, have been set up working groups for harmonization and standardization of methodologies developed and in order to define how their use in different situations. It is also noted even if available the methodologies for assessing the input-output (as for example the Life Cycle Assessment - LCA) may be redundant and excessively costly in terms of economic resources, both human because the evaluation is not limited to these three aspects (EEE) of the agro-energy chains but investigates also other perspectives (eg. eutrophication, acidification, etc.) for which the search parameters calculation is even more difficult if not impossible. It follows that, in literature, regarding the same agro-energy chain can easily find different results, even divergent. These discrepancies suggest that doubts and uncertainties in decision making, depend primarily by the non-use of the same calculation methodology, but they are also found in tests carried out homogeneously by using the same methodology. The development of an analytical calculation model, able to fill those gaps and perform a detailed analytical assessment, thus provides a working tool that optimizes the choice between different agro-energy chains and allows to detect, in each operational situation, the one offering the best overall sustainability. The objective of the project is to define a calculation method based on indications recently provided by major international working groups (the Kyoto Protocol, IPCC, Task38, etc.), its subsequent implementation through the development of a model calculation and its utilization in order to evaluate the most widespread agro-energy chains. This model calculation, flexible and easy to use, will be able to determine: - Economic Balance (Outcome/Costs); - Energetic Balance (EOUT/EIN); - GHGs Balance (t CO2AVOIDED/t CO2EMITTED). These balances (briefly "budgets EEA") are calculated by analyzing the flow - incoming and outgoing - of mass, energy and emissions of greenhouse gases (GHGs - CO2, CH4, N2O expressed in terms of CO2 equivalent) related all the phases of the agro-energy investigated. To this end, however, it is necessary to advance the development of a methodology to calculate specific, uniform and flexible and the detection of conversion parameters homogeneous and characteristic of our agri-territorial system. These methodological steps are essential to allow the analysis of the various conversion technologies currently available and to make comparison of their performance. Furthermore, the model must allow the integration of the energy and environmental performance with economic and technical ones, giving way to represent the overall sustainability of the various technology solutions combined with energy generation from dedicated biomass and agricultural byprodutcs. This index is a real index of general efficiency that, combining all aspects associated with each currently viable technical solution allows to quantify the ability to contribute to the improvement of the agricultural system in terms of, first, diversification and increase the value of products (output) and, second, direct or indirect reduction of inputs (input). Through the overall sustainability is possible to make a strict comparison of the various solutions currently available to the agricultural sector in the field of energy conversion of its residues (crop byproducts, wastes) and, consequently, to assess the real capabilities that these agro-energy may have in improving the efficiency of agriculture not only in terms of diversification and increased value of products leaving the system, but also in reducing the direct or indirect input. In order to obtain specific parameters able to be used in the calculation model some different field tests have been carried out to determine technical-economic and energetic-environmental characteristics of operative machines employed in the field phase of the chains. Subsequently, by using the software the most common agro-energy chains have been evaluated.