The report states that last year 62 trillion spam emails were sent in 2008 and the energy used to sent and delete them could power 2.4 million homes. Each spam email generates 0.3 grams of carbon, both from the power to send it and from the recipient to delete it.
The company estimates that spam filters can cut the carbon footprint of spam by 75 per cent but advocates shutting down spam at source. It says that after the McColo shutdown spam levels dropped precipitously, which gave an unexpected environmental benefit.
“The most obvious benefit of the shutdown for practically anyone with an email address was an immediate reduction in unsolicited junk messages,” the company said.
“At the same time, the planet experienced a less obvious environmental benefit. For every spam email not sent, an associated reduction in electricity use, and therefore carbon emissions, took place.”
Overall the shutdown saved enough energy to be the equivalent of taking 2.1 million cars off the road.
Businesses are taking a financial hit from spam the report finds. A typical medium sized firm uses 50,000 kilowatt hours (kWh) to run its email system but over a fifth of that power is used to deal with spam.
The average business email user is responsible for 131 kg of CO2 per year in email-related emissions and 22 per cent of that figure is spam-related. Users viewing and deleting spam is the largest energy drain associated with spam, almost 18 billion kWh or 52 per cent of total spam energy.