Emergy evaluation and the management of systems towards sustainability: A response to Sholto Maud

Abstract

Dr. Maud’s letter introduces many interesting aspects andquestions that are worth clarification. The fact that a mereeconomic management of productive systems is leadinghumanity to the destruction of the planet is, in our opinion,quite clear. Sustainability is a complex concept that needs tobe addressed with a complex approach. One singularfunction, although very suitable, will never be exhaustiveand able to explain all the aspects of sustainability.1. AssumptionsThe authors agree with the two assumptions made by Dr.Maud:A. Emergy evaluation is the holistic approach mostappropriate for analyzing the systems that are at theinterface between natural and human systems. Agricul-tural and zootechnical systems are therefore those inwhich emergy evaluation best expresses its potential.Nonetheless, it is not an omni-comprehensiveinstrumentable to focus on every particular aspect of a system.B. Both poultry systems have a good economic response,the conventional for the lower cost of production, theorganic for the increasing demand of this type of food,especially in top level restaurants.One point, for which we have a different opinion, is abasic aspect of sustainability: according to Dr. Maud, itseems that sustainability is the sum of ecological andeconomic aspects, and that the two aspects should beconsidered separately. We think that the two aspects have adifferent hierarchical value: economic advantage can beinduced or driven by laws, social behaviors, politicaldecisions, etc., if (necessary condition) ecological–physicalsustainability is already achieved. If we consider a systemthat is not economically profitable but ecologicallysustainable, a change in the socio-economic frameworkcan (and should!) enhance economic performance, main-taining the same physical conditions. The contrary, however,is not true: if the goal is economic profit, someenvironmental aspects could be irreversibly damaged. Atmost, we may have a ‘‘compatible’’, but not a sustainable,development.2. The EmMoney use in Emergy evaluationFrom a theoretical point of view, a direct link betweenemergy and economic values is represented by the so-called‘‘emergy-to-money ratio’’ (EMR), which is calculated as theratio of the total emergy flow to the related monetaryevidence. It is expressed in sej/[currency]. Its expression isderived from a macro-systemic (i.e. a nation or a region)analysis by dividing the total annual emergy by the grossdomestic product (GDP). Therefore, EMR depends on thetotal emergy flow, GDP, prices and exchange rates amongcurrencies. Only emergy is directly related to physicalentities. The others are determined by market dynamics.Hence, when EMR is used as a conversion factor to measurethe emergy related to money flows, the market partiallyaffects the emergy content of some flows, arbitrarilyeliminating or creating a portion of emergy.