I must say, I felt quite smug when I opened the envelope containing my annual electricity statement today to learn that I'd saved 482 kg of CO2 during the past year. No idea how you can quantify such things in weight, given that CO2 is a colourless, odourless gas. Anyway, the block of flats I moved into four and a half years ago apparently uses electricity from renewable sources, i.e. hydroelectric plants situated relatively nearby. Not that I had any say in the matter, but it's nice to know.