I was intrigued by Gary Sogot’s suggestion (letters, November 20) that recycling collections might use more energy than they save.

Modern cars are equipped with engine control systems designed to maximise fuel efficiency and so even a 2.5-litre petrol engine idling for an hour might only burn half a litre of fuel on a bad day. On this basis, 18 average cars left waiting for 20 minutes behind a recycling lorry would struggle to use three litres between them. Three litres of petrol represents about 95 megajoules – roughly the energy required to recycle 4kg of PET or 100 two-litre bottles. A standard wheelie bin has a capacity of 240 litres and so can, in theory, hold 120 such bottles. Mr Sogot’s recycling lorry would therefore only have to collect a single wheelie binful of plastic bottles to break even.

Of course, it’s not as simple as that, as the recycling lorry will also be consuming diesel and collecting paper, cardboard and metal, all of which have a different energy profile to plastic. Mind you, recycling reduces pollution as well as energy consumption so, on balance, it seems unlikely that a 20-minute delay would amount to an environmental catastrophe. Rather than complaining about recycling, we’d all be better off encouraging the use of public transport. I’d have more sympathy for someone stuck for 20 minutes behind a recycling lorry if they were on a bus at the time.

Amanda Horner, Oxford Street, Ramsbury.