What is the optimal and sustainable lifetime of a mine?

The first stage of the circular economy, mining, is examined from the perspective of sustainability. The authors discuss how to maximize the use of phosphate rock, a primary commodity. To attract investment capital in a market economy system, a mine has to operate profitably, i.e., its lifetime must be optimized under economic conditions, for example, according to Taylor's Rule. From a sustainability perspective, however, the lifetime should extend as long as possible and the grades mined be as low as possible. The authors examine methods for optimizing a mine's lifetime under economic conditions according to practical experience and learning effects to optimize exploration and exploitation. With the condition of sustainability, a recently developed concept of cut-off grade for a layered phosphate deposit is examined and considerations for prolonging a mine's lifetime are discussed. As there are big losses from the current and potential future value chains above and below the current cut-off grade, we argue that the losses and use efficiency of phosphorus are key parts of a circular economy

Although there is no physical short-term scarcity of phosphorus, its resource efficiency should be improved

The German government has adopted a law that requires sewage plants to go beyond the recovery of phosphorus from wastewater and to promote recycling. We argue that there is no physical global short- or mid-term phosphorus scarcity. However, we also argue that there are legitimate reasons for policies such as those of Germany, including: precaution as a way to ensure future generations' long-term supply security, promotion of technologies for closed-loop economics in a promising stage of technology development, and decrease in the current supply risk with a new resource pool

Can ultimate recoverable resources (URRs) be assessed? Does analyzing declining ore grades help?

Inspired by a paper by Teseletso and Adachi (Miner Econ 8(10):21, 2021), the hypothesis regarding the declining grade of mined copper ore and its possible use as a guide to the future of ultimate recoverable resources (URRs) is tested. As a time axis, cumulative production is taken. Grades can be either grade of cumulative tonnage or annual production grade. Correlation can be linear (grade and tonnage) or semi-logarithmic (grade linear, tonnage logarithmic). We first show that the assumption that the highest correlation is the best guide to the future may be a fallacy. This is the linear correlation between grades of cumulative tonnage and cumulative tonnages since 1959, i.e., 85% of all copper mined historically with a near-perfect correlation approaching one (R-2 = 0.97). This leads to implausibly low results of the URR, clearly demonstrating that this trend must shift in the future. Moreover, Teseletso and Adachi's (Miner Econ 8(10):21, 2021) approach using a linear or semi-logarithmic correlation between annual grades with cumulative production leads to erroneous results. Here, the later the calculation of the correlation begins, the lower the extrapolated tonnages are at predetermined, postulated ultimate cutoff grades. This contradicts the accepted knowledge that with lower grades, the resource base is broadened-not narrowed. The only reasonable finding results from the correlation between linear grades of cumulative production with logarithmic cumulative production, i.e., the Lasky relationship, indicating a URR of 7.5 GT Cu, of which 6.7 GT remain to be mined, which is equivalent of close to 325 years of present production. The trend towards declining Cu grades with constant real Cu prices shows the potential for creative solutions for other metal as well.ISSN:2191-2211ISSN:2191-220