Abstract
Extended exergy accounting (EEA) is a methodology which estimates the extended exergy cost (EEC) of a product or a service or the extended exergy efficiency (EEE) of a country or economic sector taking into account materials, energy, labour, capital, and environmental impact. The use of EEA results for policy or planning purposes has been hampered by: (1) the lack of data to quantify the EEC of most of the inputs, making it almost impossible to quantify the EEC of a product or service and (2) the lack of a conceptual framework to quantify in a consistent way the exergy of labour and capital. In this paper, we make a review of past studies to identify, synthesize, and discuss the different EEA methods. We identified 3 different EEA methods, that we further compare using the Portuguese Agriculture, Forestry, and Fishery (AFF) sector from 2000 to 2012. The equivalent exergies of labour and capital estimated for the AFF sector vary widely among the three EEA methodologies. We propose and test a new EEA methodology to estimate EEE which accounts for these fluxes in a more restricted scope but more consistently and that includes the Environmental Benefit (EB) that represents the capability of the forestry to capture carbon dioxide. Results show that the EEE of the Portuguese AFF sector has increased by 32% from 2000 to 2012.
Highlights
The rapid depletion of the natural environment and the will to ensure the survival of present and future generations led mankind to study and address new ways to improve the efficiency of using earth finite resources
We propose and test a new Exergy Accounting (EEA) methodology to estimate exergy efficiency (EEE) which accounts for these fluxes in a more restricted scope but more consistently and that includes the Environmental Benefit (EB) that represents the capability of the forestry to capture carbon dioxide
We propose an Intrinsic Extended Exergy Accounting (IEEA) approach to estimate the Extended Exergy Efficiency (EEE) of products/services or sectors that (1) values labour and capital flows more consistently and (2) does not need an Exergy Cost (EEC) database
Summary
Thermodynamic concepts widely adopted to measure the efficiency of industrial processes are being increasingly used to assess the efficiency and sustainability of other societal processes at different scales. Acknowledging that our societal relation with the global environment is above all made through physical interactions, the thermodynamic concept that is better able to measure the quality of these interactions is exergy. In contrast to energy, which is subject to a conservation law and suitable for quantity measurements, exergy is destroyed in any real interaction process, due to irreversibilities, and is absent from conservation principles. By aggregating the energy of different flows entering and leaving a system, the energetic assessment of the system tells only a partial story since the quality of such flows is not taken into account. Exergetic assessments measure all flows by taking into account their quantity and quality
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