In this book we analyse the sustainability question in the Modern Production System, which today encompasses most of the world economy. We present concepts, theories, indicators, indices, formulas, methods and historical date to examine the evolution and trends of two sustainable development dimensions: socioeconomic and environmental. We focus on the nature-economy nexus and analyse its contradictory process: the more the economics needs nature, the more its cause natural resources depletion and environmental degradation. The huge increase on CO2 emissions in the last three decades – from oil, coal and another non-renewable resources– provides strong evidence to such contradiction. We then analyze the role of material recycle as a solution against both, resources depletion and environmental degradation. Our analysis suggests that the recycle of materials can only contribute to reduce the problem. Moreover, there cycle process of materials depends, on many cases, of public or social subsidies – as financial incentives from the government and domestic material selection. The environment problem transcends borders (as an enterprise, a village, a city, or a country): one can be sustainable, but in fact transfer to other its environmental problem. We adopt the notion of Environmental Space to deal with the sustainability question. We then present and apply the concept of Eco-inequal Exchange to analyse such a question. The environmental movement, which started about fifty years ago, did transform the sustainable development into a global mission. By exposing socio-environmental problems generated by the modern production system itself, this book aims to contribute to a better understanding the limits and possibilities of ours actions as environmentalists.