A letter produces about two to three times as much carbon dioxide as an email. Producing the paper for an A4 letter and envelope, along with transport and disposal, generates an average of 20 to 30 grams of carbon dioxide. An email with the same amount of information stays well below 10 grams of carbon dioxide. Emissions are generated by the production and operation of data centers, network infrastructure, and end devices.
However, CO2 emissions naturally depend on the energy mix: The less fossil energy is used to produce electricity, the lower the emissions. In 2024, the total number of letters sent worldwide is estimated at less than 300 billion, which together produced 0.009 gigatons of carbon dioxide emissions. In the same period, 350 billion emails were sent every day, which adds up to 0.17 gigatons over the year. So, while a single email produces less carbon dioxide than a letter, we send far more emails per day – and the trend is rising.
Dr. Markus Maisch, Geo and Environmental Research Center (GUZ), University of Tübingen
