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The environment may constrain economic growth potential. In other words, economic growth cannot be pursued in spite of ecological limits any longer. Here we present an economic growth indicator adjusted by taking into account the current tendency of national economies to overcome the availability of natural resources and ecological dynamics. We combine two indicators: 1) the Output Gap, a measure of production capacity of the economy based on the difference between actual and potential GDP, as a per cent of potential GDP; 2) the difference between the Ecological Footprint and the Biocapacity of a country, systemic indicators representing the extent to which a country operates within or beyond ecological limits. That combination gives rise to the Biocapacity Adjusted Economic Growth indicator which enables a categorization of countries based on assessment of growth patterns in line or not with sustainability principles.

Due to growing interest in biofuels as alternative renewable energy sources, several recent studies have assessed the sustainability of their production. Emergy is a widely used environmental indicator for this purpose, as it counts exploitation of natural resources and direct and indirect solar energy requirements of biofuel production. Depending on whether a biofuel is first, second or third generation, its production system differs in nature and the indications derived from emergy evaluations vary as well. This article aims to provide guidelines on how to interpret and properly use the results of emergy evaluation of first, second and third generation biofuels. These guidelines are useful for correct emergy assessment of biofuels and clarify the actual meaning of emergy evaluation outcomes.

The comparison of the Ecological Footprint and its counterpart (i.e. biocapacity) allow for a classification of the world's countries as ecological creditors (Ecological Footprint lower than biocapacity) or debtors (Ecological Footprint higher than biocapacity). This classification is a national scale assessment on an annual time scale that provides a view of the ecological assets appropriated by the local population versus the natural ecological endowment of a country. We show that GDP per capita over a certain threshold is related with the worsening of the footprint balance in countries classified as ecological debtors. On the other hand, this correlation is lost when ecological creditor nations are considered. There is evidence that governments and investors from high GDP countries are playing a crucial role in impacting the environment at the global scale which is significantly affecting the geography of sustainability and preventing equal opportunities for development. In particular, international market dynamics and the concentration of economic power facilitate the transfer of biocapacity related to "land grabbing", i.e. large scale acquisition of agricultural land. This transfer mainly occurs from low to high GDP countries, regardless of the actual need of foreign biocapacity, as expressed by the national footprint balance. A first estimation of the amount of biocapacity involved in this phenomenon is provided in this paper in order to better understand its implications on global sustainability and national and international land use policy. Refereed/Peer-reviewed

An evaluation of the investment required to implement a second generation bioethanol production chain is presented in this study. An integrated agro-industrial system can be an appropriate solution to accomplish the European requirement for the partial substitution of bioethanol for gasoline by 2020. A biorefinery system is hypothesized within the Province of Siena (Italy), fed by residual energy and material flows from local productions: straw from agriculture and residual geothermal heat from geothermal electricity generation; the output is calibrated to replace 10% of gasoline consumption within the Provincial area. The physical consistency of the investment required to implement the production process, as well as the benefit of the biofuel–gasoline substitution, have been evaluated by means of the emergy methodology. Emergy is a thermodynamics-based indicator that contributes to identify and measure all the inputs supporting a given system, expressed in a common unit (solar emergy Joules – semj). Results show that the benefit of saving gasoline, in emergy terms, almost doubles the emergy investment to produce biofuel. The case of a biorefinery fed by natural gas instead of local residual geothermal heat is also presented. The Unit Emergy Investment (UEI) of bioethanol produced in a biorefinery that uses residual straw and geothermal heat is 9.16E + 08 semj/g (the case of the Province of Siena); it is 1.84E + 09 semj/g (in case natural gas is used to fuel the process). Finally, the comparison between the UEI of bioethanol evaluated in this study and UEV of bioethanol calculated in other studies is presented.