Question 1: 1.167 billion smartphones (rounded to 1.2 billion) sold annually: Jon Porter, “Apple tops Samsung for first time in global smartphone shipments,” The Verge, January 16, 2024, accessed at https://www.theverge.com/2024/1/16/24039830/apple-bestselling-phone-manufacturer-2023-samsung-idc-canalys-research; less than three years: Federica Laricchia, Statista, Average Lifespan (Replacement Cycle) of Smartphones in the United States from 2013 to 2027, accessed at https://www.statista.com/statistics/619788/average-smartphone-life/, August 26, 2024.
Question 2: Neodymium in smartphones: Based on 0.22 g Nd/smartphone multiplied by 1.167 billion smartphones sold annually. Total is 257 metric tons, rounded down to 250 metric tons. 0.22 g Nd/smartphone assumes Nd = 0.2% of smartphone by weight and smartphone weight is 110.74 g, from B. Bookhagen, et al., “Metallic resources in smartphones,” Resources Policy 68: 101750, October 2020, https://doi.org/10.1016/j.resourpol.2020.101750). 5% of all neodymium used in electric vehicles worldwide based on 5.16 kilotons used in electric vehicles in 2023 from International Energy Agency, Critical Minerals Data Explorer, accessed at https://www.iea.org/data-and-statistics/data-tools/critical-minerals-data-explorer, August 26, 2024.
Question 3: 38.4 kg/turbine based on 12 kg/MW for onshore wind turbines from Annika Eberle et al., National Renewable Energy Laboratory, Materials Used in U.S. Wind Energy Technologies: Quantities and Availability for Two Scenarios, August 2023, archived at https://web.archive.org/web/20240327163343/https://www.nrel.gov/docs/ fy23osti/81483.pdf, p. 38; multiplied by average size of new wind turbine of 3.2 MW (in 2022), from Liz Hartman, U.S. Department of Energy, Wind Turbines: the Bigger, the Better, August 21, 2024, archived at https://web.archive.org/web/20240826172916/https://www.energy.gov/eere/articles/wind-turbines-bigger-better. 257 tons (from Question 2 above)/38.4 kg = 6,692 turbines. Increase of 50% in lifespan = reduction of up to 33% in material use. 6,692/3 = 2,230 turbines, rounded to 2,200. Number of average homes from U.S. Geological Survey, “How many homes can an average wind turbine power,” Frequently Asked Questions: Energy, undated, archived at https://web.archive.org/web/20240826173511/https://www.usgs.gov/faqs/how-many-homes-can-average-wind-turbine-power.
Question 4: Oranges: Jillian Kubala and Atli Arnarson, “Oranges: Nutrients, benefits, juice and more,” Healthline, updated April 20, 2023, accessed at https://www.healthline.com/nutrition/oranges; volleyball: topend sports, Sports Ball Weight Comparison, undated, archived at https://web.archive.org/web/20240826173950/https://www.topendsports.com/resources/equipment/ball-weight.htm, August 26, 2024; hamster: Hamster Clubhouse, “Healthy weight range for hamsters?”, January 14, 2023, accessed at https://hamsterclubhouse.com/forum/viewtopic.php?t=866.
Question 5: 18%: Douglas S. Thomas, National Institute of Standards and Technology, Cost-Effective Environmental Sustainability: A Focus on a Circular Economy, October 2022, archived at https://web.archive.org/web/20240327182944/https://nvlpubs.nist.gov/nistpubs/ams/NIST.AMS.100-48-upd1.pdf, p. 16.
Question 6: Copper saved from We Don’t Need Deep-Sea Mining, page 36; copper intensity of residential PV systems = 8,303 lbs./MW from Roberto Rodriguez Labastida and Dexter Gauntlett, Navigant Research, North America Solar PV Copper Content Analysis, 3rd quarter 2018, archived at https://web.archive.org/web/20240826175107/https://www.copper.org/publications/pub_list/pdf/a6197-na-solar-pv-analysis.pdf; median residential PV system = 7.2 kW from Galen Barbose, et al., Tracking the Sun: 2023 Edition, September 2023, https://web.archive.org/web/20240826175705/https://emp.lbl.gov/sites/default/files/5_tracking_the_sun_2023_report.pdf, p. 12; copper per residential system = (3.77 metric tons/system × 7.2 kWh)/1000= 0.027 metric tons/system. 20,590/0.027 = 762,592 systems, rounded to 760,000; one-fifth of total number: 3.9 million residential solar energy systems from David Feldman, et al., National Renewable Energy Laboratory, Spring 2023 Solar Industry Update, April 27, 2023, archived at https://web.archive.org/web/20231114215848/https://www.nrel.gov/docs/fy23osti/86215.pdf.
Question 7: 52% and 25% from Fatma Romeh, et al., Centers for Disease Control and Prevention, “E-cigarette unit sales by product and flavor type, and top-selling brands, United States 2020-2022,” Morbidity and Mortality Weekly Report, 72(25): 672-677, June 23, 2023, accessed at https://www.cdc.gov/mmwr/volumes/72/wr/mm7225a1.htm?s_cid=mm7225a1_w.
Question 8: 11,000: Oliver Barnes and Alexandra Heal, “The environmental cost of single-use vapes,” Financial Times, March 7, 2023.