THE HUMAN NATURAL RESOURCE ENDOWMENT OF LIMESTONE AND THE LIMITS OF CEMENT PRODUCTION

The Human Natural Resource Endowment (HNRE) was used to interrogate dynamics of global limestone resources for Portland cement production. HNRE represents resource depletion by measuring resource allocation per capita and lifetime of resource allocation. HNRE was calculated by subtracting annual limestone production from the ultimately recoverable reserves then dividing the difference by global population from 1926 to 2019. The global limestone resource is prodigious (est. 6.65 x 10²⁰ kg), though not all limestone is suitable for Portland cement production. To account for limestone suitability for Portland cement production, scenarios that reduced limestone reserves in 10% decrements from 90% to 10% suitability were modeled. Results for all scenarios showed substantial decline in HNRE over time, though remaining reserves in each scenario were orders of magnitude greater than reasonable estimates of future Portland cement needs. Thus, limestone reserves for Portland cement may be an example of a truly inexhaustible resource. Despite the apparent inexhaustibility of limestone reserves, the global supply of Portland cement was paradoxically insufficient to meet global demand each year during the past decade, and global orders for Portland cement remained unfilled. Given large known reserves of limestone, the inability to meet demand for Portland cement suggests the global cement-manufacturing industry is at capacity. Thus, global production capacity limits resource exploitation. This example illustrates that resource limitations sometimes arise from human dimensions of resource access and allocation rather than physical dimensions of abundance and availability. Thus, human dimensions of resource dynamics are also important when modeling natural resource sustainability.