Spammers have a bad reputation. In most cases, deservedly so.

I knew spam was a problem – my own spam filter currently has 1,824 messages languishing in it – but I didn’t think that things had got this bad. Not only do they clog up your inbox, but spammers can now be blamed for killing the planet too.

Apparently, someone in McAfee thought it would be a good idea to work out how much junk mail is winging its way to our inboxes each year, and exactly what impact it has on the environment.

Bad news, spammers: the carbon footprint brigade have you in their sights.

According to the Carbon Footprint of e-mail Spam report compiled by ICF International, about 62 trillion spam emails were sent in 2008, and spam accounts for about 80 per cent of all email messages sent. Creating, sending, receiving and storing junk mail uses more than 33 billion KWh of energy, generating 17 million tons of CO2 emissions.

That irritating spam filter that occasionally bins a legitimate mesage might be helping to save the planet. Apparently spam filtering can save 135 TWh of electricity every year – the equivalent of taking 13 million cars off the road – and if every inbox was protected by a “state-of-the-art” spam filter, spam energy usage could be cut by 75 per cent, or 25 TWh per year. The equivalent of taking 2.3 million cars off the road, fact fans.

Spam filtering, on the other hand, accounts for only 16 per cent of spam-related energy use.

So to summarise: spam bad. Very bad.