**Acknowledgements**

technologies, from the bare rock to the ore grade conditions of the mine. This depletion indicator can be used for all fossil fuels, and minerals no matter their chemical composition and concentration. Fossil fuels must be replaced with renewable energy sources and need to be accounted for such progress. In the same way, stopping depletion of metals will largely come from techniques such as designing for recyclability, reducing the number of alloys used, avoiding the design of monstrous hybrids, designing for disassembly, symbiosing industrial complexes, increasing the efficiency of smelters to avoid metal losses in slags, increasing the throughput of scrap, etc., (see [19, 20]). All these techniques decrease

The idea of replacement, restoration, remediation or repair exergy could easily be extended to indicate the depletion of many other non-renewable resources of biogeological origin like the loss of forests, landscapes, fertile soil, subsoil waters, fisheries, climate change, etc. The amount of work needed to restore what was degraded should be accounted for, even if it will hardly be restored. It is like a debit account for future generations. Each time we learn how to accomplish replacements

If "prevailing technologies" are a reflection of embodied knowledge, we will see to what extent they decrease our debt with future generations. Nevertheless, it is not clear that any new technology that directly or indirectly improves efficiency in production processes decrease our debt. The rebound effect goes always in the opposite direction; the more efficient

Valuing our technological improvements is as important as conservation of resources. Conservation is something else than repair, restoration, or replacement. It requires a change in our lifestyle through education. Education is an indispensable tool for technological innovation and conservation. And it is not clear yet, which of both are more important at any historical moment in man´s life on the planet. Conservation and technological improvement can be accounted for with the proposed theory. Consequently, the second law of thermodynamics

If replacement can be calculated and registered for almost any action of man on the planet, we need an international framework to provide concepts, definitions, classifications, accounting rules and standard tables for all countries. The System of Environmental-Economic Accounts (SEEA) of the United Nations may well provide such statistical framework. As explained previously, the System of National Accounts (SNA) is an established system for producing internationally comparable economic statistics, which imposes the organization and standardization of domestic accounts. It is widely accepted and established worldwide. Bureaus of statistical office (BSO) for data recovering and economic accounting exist in almost any country. Companies and countries report economic and physical data following the established accounting procedure, and BSOs integrate them. It is a huge infrastructure. From households to companies and to countries, these accounts are presented in money values. SEEA follows the accounting structure of the SNA thus facilitating the integration of environmental statistics with economic accounts. Thus, each national BSO needs to take the responsibility for the environmental data recovery and environmental-economic accounting too. However, these offices are mainly composed by economic statisticians, which are used to convert their assets into money values. When describing the physical tables needed for SEEA, we have seen

or recycling or how to live with less, is like slowing the time machine toward Thanatia.

we are the more consumption is promoted (see, for instance, [21]).

ought to be placed at the core of economists' literacy.

depletion and must be accounted for too.

74 Sustainability Assessment and Reporting

This chapter has been financed by the TRIDENTE project from the Spanish Ministry of Industry and Science.
