Final Activity Report Summary - EMPHORES (Efficient Management of Phosphorus Resources: Long-term Allocation of an Essential Non-Renewable) Nutrient depletion and pollution impact global anthropogenic change. This project dealt with the regional and inter-temporal distributions of the macronutrient phosphorus (P). P is an essential nutrient for life and a key non-renewable resource because its use as fertilizer cannot be substituted. In order to effectively conserve the non-renewable P resource, flows and stocks of P should be known at national, regional and global scales. For this, a material flow analysis (MFA) model was proposed in this project, combining resource and waste management. The country-scale model emphasised resource use while showing overall P-flows, stocks and their changes. It provided knowledge of country-specific characteristics of the P-metabolism. For quantification, statistical data from economic and agricultural sources as well as available information about P partitioning in natural and anthropogenic processes were used. Special attention was paid to data gaps and uncertainties. This model was tested in two case studies on P management in Turkey and Austria. MFA appeared to be a well suited tool for establishing country-wide P balances, provided that national statistics were well-structured and accessible. Using the model as a common approach for describing P flows and stocks, regional and national balances could be compared and linked towards larger scale P balances for an improved management of the resource. At the global scale, we dealt with an essential input into agriculture with no substitute. Clearly, international and inter-temporal P allocations had an impact on food security. To address this issue, we built an extraction and recycling model for P as a single resource. Our model extended the simple cake-eating model of resource extraction. We built the characteristics of the resource, namely its non-substitutability and essentiality into the model in the form of an isoelastic demand function and in terms of a lower bound on demand. As high quality phosphorus mines were depleted, recycling gained importance and industrialised countries explored new technologies for P recycling. Because there was no substitute apart from some recycling possibility, this option introduced a resource augmenting technology into the dynamic optimisation framework. This part of the project dealt with three important issues that were neglected in resource economics, namely the essentiality of a resource, the theoretical gaps with respect to the value of the resource and the importance of long-term recycling of a non-renewable resource within a dynamic optimisation framework. Our approach investigated the long-term effects of phosphorus recycling in two model variants: 1. a two-country model, where we analysed the effects of P recycling in industrialised countries on the prices and imports of developing countries. This was a model of a competitive fertiliser market that reflected the fact that most industrialised countries had P-saturated soils while soils in many developing countries were P-deficient. We considered two countries that differed in their demand and recycling options. We observed that P recycling in industrialised countries did not only prolong the resource life-time, but also increased the developing countries share of the resource. 2. a global model, where the opportunity costs of using the resource changed over time in a way that led to non-monotonous extraction paths as the efficient solution. We assumed progress in extraction technologies along with a stock effect. We found that essentiality exhausted the resource even if the latter was non-substitutable and that recycling postponed depletion costs. Moreover, with fast enough progress in mining technology, prices gave the wrong scarcity signals for recycling and, finally, using shadow price to signify the increase in scarcity, we observed that early adoption of recycling technologies was the preferable option.