Q I’m a sucker for fairy lights, but do they waste too much energy?

A Stick with a modest string of LED or low-energy fairy lights and you’ll be environmentally beyond reproach. They use a quarter of the energy of normal ones and last much longer. To avoid transport emissions, acquire them from ecocentric.co.uk for posh designer ones (£39 for a string of 30), or for a cheaper option, buy from lights4fun.co.uk (£15 for a string of 40).

But it sounds as though you had more than one set in mind. An illuminated tree is not enough for some people; there are window displays and fireplaces to think about. In which case you are forgiven, so long as you turn them off overnight and when you are out, rather than leaving them flickering 24 hours a day. An automatic timer will make this job easier.

Stray into illuminated Santas and flashing reindeer territory, however, and I’m going to have to put my foot down. It all adds up.

Given that 90 per cent of households leave their Christmas lights on 24 hours a day, this time of year can end up being an energy drain, especially when you factor in trying to keep the house warm and badly behaved relatives leaving the bedroom lights on.

According to the Energy Saving Trust, over the 12 days of Christmas, a typical string of lights left on for ten hours a day would produce roughly the same amount of carbon dioxide as two dishwasher cycles. That’s 1.44kg – not much on its own, but this figure jumps to 32,000 tonnes overall in the UK.

One way you could feel better about it is by turning off other lights. I have a friend who likes to watch television with all the lights off. Saving electricity is part of it, but it also helps her to focus on what she is watching.

Why not do a similar thing with fairy lights? Instead of diluting their twinkly splendour, have a fairy-lit evening. Cooking might be a challenge, but eating and talking will be easy. Dimly flattering, even. And all those things you can’t do by fairy light . . . sometimes it’s nice not to do them anyway.

Q My council collects food scraps in a special bin. I’m wondering what happens to them?

A I can’t speak for your council, but I can tell you about the journey that my chicken bones and burnt toast make after they are scooped up by a green lorry each week. It is a typical process used for composting large quantities of organic matter, although I gather that I am lucky to live the right side of town – East London – which means that my council is served by the pioneering EcoPark Compost Centre in Edmonton, North London.

Opened last year, the 40-acre site aims to process 30,000 tonnes of waste from seven London boroughs every year. In other parts of the UK, you might find that your food scraps have to travel farther to be deposited at the closest processing centre, thereby clocking up a heavier carbon footprint.

As for mine, when they arrive, they are blended with garden waste before being piled into one of 16 concrete huts. These innovative structures (known as “vessels”) are roughly 3mx4m (10ftx13ft), with Gor-Tex roofs that allow the material to breathe – crucial in the composting process. They are fanned by underground air blowers that also introduce air into the compost, speeding up the breaking-down process.

After three weeks, the compost has reached a high enough temperature to kill any bugs, so it is transferred to another vessel for a further three weeks of rotting.

The final stage involves leaving it outside where it matures for anything up to three months, before being sieved to remove any bits that shouldn’t be in there in the first place, such as plastic. This rich compost is then distributed to allotments, local parks and farmers.

It sounds like a mucky job, shovelling other people’s peelings, but Julian Appleby, the waste operations manager at the centre, is unfazed. “It’s wonderful stuff,” he tells me, admitting that he’s a bit of a composting bore.

“We’re taking organic material that for generations we’ve stuffed into landfill and turning it into something useful,” he raves. Having witnessed friends glaze over when I start up about the wonder of my wormery, insisting that it smells earthy and natural, I sympathise.

DO IT

Buy a jute shopping bag from the ethical hamper company Turnham Green (£15) and it will donate money to Garden Africa ( gardenafrica.org.uk ) to buy beehives, a worthy cause given The Grocer magazine reports on a global decline in bee numbers. The hampers are full of ethically sourced goodies from fiery tomato chutney and spiced biscuits ( turnham-green.co.uk ).

CLICK IT

If your walk to work involves a polluted main road, you’ll be happy to hear that walkit.com , judged by Time Out magazine to be one of “50 websites to change the world”, has launched a map generator that offers a “less busy” route. It will also estimate the number of calories you will burn and the carbon you will save.

SKIP IT

Procter & Gamble has been shown up by the Greenpeace guide to forest-friendly tissues, kitchen roll and toilet paper ( greenpeace.org.uk/forests/tissue-guide ). Rating products according to whether they are certified by the Forest Stewardship Council or made with recycled paper, P&G gets the lowest. M&S and Sainsbury products are the greenest.

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