Can you reduce your carbon footprint with a vegan diet?

The first week was the hardest. As winter set in, the usual ports of call for comfort eating (the chocolate counter of the newsagents and the Jewish bakery at the end of my street) became no-go zones. Instead of dreaming the things that normal 30-year-old women dream of (shoes, obviously), I began fantasising about buttery scrambled eggs and crumbly feta. One night I cracked, leaping out of bed to raid the biscuit tin. But next morning, reality bit or rather, I bit reality, and it tasted like cornflakes with soya milk, followed by toast and dairy-free spread (hold the honey because collecting honey kills bees). Welcome to the world of a vegan.

So why would someone who believes cheese has magical healing powers decide to take the dietary equivalent of a monk's vows? Well, evidence is mounting that meat-eating might be the next casualty in the war on climate change. According to a UN report from 2006, raising animals for livestock generates more carbon emissions than all the world's transport (including aircraft) put together: 18 per cent, to be precise. Meanwhile, a recent report from the Food Climate Research Network at the University of Surrey states the meat and dairy industry accounts for 8 per cent of UK carbon emissions (to put that in perspective, the airline industry accounts for 2.5 per cent). Researchers from the University of Chicago have calculated that an average meat-eater emits 1.5 tonnes more CO2 per year than a vegan, because it takes, for example, 7kg of feed to produce 1kg of beef. Not to mention all that methane yes, the farting cows and nitrous oxide.

The scientists have spoken, and the politicians are getting edgy. Vegetarian campaigning charity Viva received a leaked email from an official at the Environment Agency showing that the Government is trying to work out how to get us to eat less meat. "The potential benefits of a vegan diet in terms of climate impact could be very significant," it said, adding that eating less meat is one of the "key environmental behaviour changes" needed to save the planet.

Soon the amount of meat and dairy we eat may become a factor in carbon footprint audits. It's easy to change our light bulbs and flip the washing machine down a notch to 30 degrees, but how does it feel to take a more radical step?

Just to recap (in case you haven't been studying Heather Mills's diet) being vegan means no eggs, no fish, no meat, no milk and no honey. Many beers and wines are also out, as they are made with a fish by-product that helps separate the sediment. This means that veganism is possibly the quickest weight-loss programme in the world, immediately cutting out a lot of the fat our bodies (well mine, anyway) crave.

As part of my induction into the ways of the non-animal eaters, a friend took me on a tour of the local health food shop. Steering me manfully past the cheese counter, he picked out a few things he knew an avid carnivore would be missing, introducing me to the delights of tempeh (a tasty soya product), syrup waffle biscuits and tofu cheesecake. "This stuff's great for a sweet-toothed girl like you," he said, brandishing a milk- and egg-free custard at me. I peered at it. "Does it taste creamy?" I enquired. He wasn't sure. He hadn't eaten cream in 15 years.

Confronted with something that resembled a tube of sun block but proclaimed itself to be "yeast pt", we sighed collectively at the still unsexy nature of vegan culture. The only food I could find which did not fall into this trap was a brand of ice cream, which came seductively packaged and looked and tasted (and, indeed, almost cost) a million dollars. That ice cream along with a spectacular vegan chocolate cake are discoveries which make me think a permanent switch might be possible. Over four weeks, I learnt to cook a respectable vegan lasagne and even discovered vegan pizza.

But the diet is tough, especially if you love food. Variations on the humble soya bean are one of the most efficient ways to get protein into a vegan diet. To avoid feeling hungry, you have to eat soya a lot of soya. I love tofu, but soya milk makes me feel sick, so I ended up drinking almond milk instead. Many people have raised concerns about the health implications of too much soya (it contains a version of the female hormone oestrogen, for example) but it's actually good for lowering cholesterol. What worried me more was the ravaging effect soya plantations have on delicate eco-systems: Greenpeace estimates between 2003 and 2006, 70,000 sq km of Amazon rain-forest was destroyed to make way for the crop. Vegans point out that the majority of soya is grown for animal feed, but if all the planet's inhabitants took the vegan vow, it's questionable whether the amount of soya needed to feed them would be any less.

Britain's 250,000 vegans pretty much keep themselves to themselves and becoming one is tantamount to joining a subculture. The reason is understandable as soon as you set foot in vegan territory. Though most restaurants offer vegetarian dishes, the chances of them coming without lashings of cheese are slim, while having a vegan to dinner sends terrified hosts into a frenzy. And try grabbing a bite to eat at a train station there is not a vegan sandwich filling to be had from Penzance to Aberdeen, let me tell you.

Not only that, but veganism itself is still viewed with deep suspicion, as though it's a slippery slope to joining an Animal Liberation Front sleeper cell (though, of course, many perfectly normal people avoid dairy due to lactose intolerance.) Mentioning the V word in public gets a similar reaction to wearing a veil somehow a very personal choice can be interpreted as a threat to life as we know it. Even though I was not evangelising about my decision to eschew meat and dairy (quite the contrary: I complained to the world that milk-free cheese tastes like the devil's toenail clippings), I found people would openly attack me about it.

Would a vegan planet be a good place? According to eminent science writer Colin Tudge, the author of Feeding People is Easy, the ideal human diet should be based on the maxim of "plenty of plants, not much meat, and maximum variety". He argues that some livestock should be integral to running farms as they can be fed surplus crops and be efficiently reared on ground which is unsuitable for other types of farming.

Tara Garnett, research fellow at the University of Surrey, agrees. "We have to make the best use of use of land in order to feed people properly and minimise environmental impacts, including greenhouse gases," she says. "Pasture land unsuitable for crops with stony, shallow soil and bad weather can support livestock. It's not practical to advocate veganism; there is no culture in the world which is vegan. Even India is a milk-drinking society. Meat is an efficient source of protein, especially for poor communities. The message to developed countries should be to eat less meat, to see it as a luxury."

Friends of the Earth also takes this line. "Livestock is a vital part of the livelihoods and diets of people around the world but we need a shift away from intensive farming and unsustainably high levels of consumption," says food campaigner Kirtana Chandrasekaran.

Whatever the scientific arguments, my attempt to go vegan for eco reasons was ultimately confounded by a lack of the moral imperative real vegans feel. While my vegan friend looks at a juicy steak and sees a cow that's been electrocuted, bashed over the head, stripped of its skin and dismembered (possibly while still alive), I just see a juicy steak: my only dilemma is whether to eat it with pepper sauce or just rare with a nice burgundy.

So I'm afraid I am exiting vegan-ville and heading straight for the farmer's market to pick up some tasty cheddar. But as climate change continues to make headlines, I may well be back and you might one day feel persuaded to join me.

How to be a caring carnivore

* Elect to eat one or two organic, locally produced cuts of meat a week rather than eating cheap processed meat every day

* Roast a chicken and live off it for a week, making stock from the bones and eating the leftovers avoiding wastage

* Investigate meat alternatives such as tofu (pictured left), tempeh, textured vegetable protein and Quorn

* Buy organic milk, or try soya (pictured right), almond, oat, hazelnut or quinoa milk instead

* Chicken and pork are more carbon-efficient and produces less methane than beef

* Be aware of other good sources of protein. These include pulses, beans, nuts, seeds and, of course, soya beans

* Many kinds of bread and even some vegetarian products contain unnecessary milk products like whey, buttermilk or lactose, or eggs. Check the packaging and avoid buying non-organic dairy by avoiding these products