1. Background The need for raising the quota of energy produced from renewable sources in the global energy balance, dominated by developed countries, is supported by a huge and growing body of literature – today easily and largely accessible 1 through the World Wide Web – and by the international legislation, where this need has finally come to be viewed as a priority. An impor- tant example is the recent EU directive promoting the use of energy from renewable sources [2009/28/EC]. Therefore, this contribution does not analyse studies or data to demonstrate the importance of renewable energy sources, which is assumed as a given, but rather discusses issues that are relevant to those who deal with the subject at the educational and the pro- fessional level, with special emphasis on Agricultural Engineering. Before delving into the subject, it may be useful to summarize the main issues involved: a) The first is the reported shrinking of fossil fuel supplies that can be extracted at reasonable cost (especially crude oil with a low content of pollu- tants, such as sulphur, available at technically reachable depths). The matter is debated, because evidence for dwindling world supplies 2 [Brias- soulis 2009] due to rising demand coexists with ar- guments maintaining that such resources are plenti- ful, but substantially conditioned by geopolitical matters, trade dynamics, and the investment poli- cies of the oil industry 3 [Maugeri 2006]. In this context, the development of renewable energy sources to replace fossil fuels has the potential to reduce the global dependence on them, which is a strategic value in itself; b) The second is the environmental issue connected with CO 2 and other greenhouse gas emissions, due to the manufacturing and use of technologies and industrial products (particularly N 2 O and CH 4 ). These are inducing climate change (for which the evidence is substantial), resulting in an altered bal- ance of multiple ecological systems as well as in social consequences, especially in the poorest countries [Global Humanitarian Forum 2009]. The use of fossil fuels essentially moves the carbon that has accumulated under the surface of the earth to the atmosphere, inducing changes in its chemical- physical characteristics, like higher permeability to infrared radiation. Views differ about these aspects, too, some researchers anticipating multiple severe consequences [Flannery 2008] and others relating these changes to natural climate cycles [Various Authors 2009]. However, support for the latter view appears to be less strong. At the political lev- el, the issue has long been discussed 4 , although greater consistency between policies and interven- J. of Ag. Eng. - Riv. di Ing. Agr. (2010), 2, 35-45 CONSIDERATIONS ON RENEWABLE ENERGY SOURCES AND THEIR RELATED PERSPECTIVES OFAGRICULTURAL ENGINEERING Ester Foppa Pedretti, Giovanni Riva, Giuseppe Toscano, Daniele Duca ___________ Paper received 11.11.2009; accepted 30.08.2010 Prof. GIOVANNI RIVA full professor, Dept. SAIFET, Technical Uni- versity of Marche, via Brecce Bianche, Monte Dago, 60131, Ancona, g.riva@univpm.it Prof. ESTER FOPPA PEDRETTI associate professor, Dept. SAIFET, Technical University of Marche, e.foppa@univpm.it Dr. GIUSEPPE TOSCANO researcher, Dept. SAIFET, Technical Uni- versity of Marche, g.toscano@univpm.it Dr. DANIELE DUCA, PhD, Dept. SAIFET, Technical University of Marche, d.duca@univpm.it ___________ 1 A Google search for “renewable energy” (with the string in in- verted commas in order to search for the words in this sequence) yields more than 17 million (M) hits; a search for “energy” produces more than 350 M hits, placing it in reassuring competition with “food” (over 600 m hits). However, when limited to PDF files (i.e. documents available for download, which are likely to be reports of a certain val- ue), the search yields more than 3 M hits for “renewable energy” and less than 55 M for “food”. These data, confined to the English lan- guage, are partial but highlight various questions, in particular the huge amount of material available on the Web. Its sheer quantity would require a summarizing effort directed at identifying relevant material for teaching purposes and for spreading research results. 2 This view is widely held, with Hubbert a major points of refer- ence (http://www.hubbertpeak.com). Given the scarcity of fossil re- sources, some authors propose focusing EU university curricula on “renewable energy sources” and “agricultural engineering”. 3 This view has a narrower following but the literature is usually highly qualified. 4 Among various actions, one in particular deserves to be men- tioned – the setting up of the Intergovernmental Panel for Climate Change (IPCC), whose remit is to study climate change and its causes. At the EU level the IPCC reports have led to an articulated body of rules aimed at reducing CO 2 emissions that will become increasingly restrictive over time.