Product reuse advances circular economy by reducing material demand. However, environmental assessments often assume reused products fully replace new ones, or they overlook market changes and shortened lifespans driven by resale and repurchase opportunities. This study presents an empirically based analysis of the second-hand smartphone market and its cumulative effects on manufacturing demand and carbon emissions. Integrating consumer survey data and product lifetime estimates in a stock-and-flow model, we find that in the United States, each second-hand transaction currently extends smartphone use time by 40%, displaces 0.40 new devices, and that circular consumption results in a 34% lower annual carbon footprint. With 25% of consumers purchasing used phones, production demand and carbon emissions are lowered by 15% and 14%, respectively. Yet, shortened use times offset nearly half the potential gains. If reuse became the norm, manufacturing demand could decline by one-third, revealing both the promise and the limits of reuse.

Data on the total product lifetimes, which is much needed in the fields of sustainability and circularity assessment, is currently sparse and challenging to measure. To meet such data and methodological needs, the first information system of its kind has been developed as part of this research. While an online portal collects and stores consumer reports on use and disposal patterns for various electronics owned and used, the harvested survey data was automatically fed into a novel stochastic model that allowed estimating the total lifetimes and durability of the different products considering the impacts of second-hand use. This was done without reliance on auxiliary market statistics and costly facility-based analysis while preserving a satisfactory degree of accuracy. Additionally, the structure of the collected data allows for measuring the effects of the different circular practices (repair, reuse, recycling, etc.) on product longevity which is of specific interest to researchers and policymakers.