Harming the environment: Jean Greenie

We all love our denims. But few of us realise that indigo dye - a by-product of the oil industry - is environmentally destructive. Now a natural alternative has been found, and you'd never know the difference. Sanjida O'Connell reports

Gracie Burnett has done the fashionable thing: moved from the city to the country so she could have a garden. But here the similarity to most downsizers ends. Burnett moved to a cottage on the edge of a wood in her native Dorset in order to create a dye garden.

"I'm just gathering my first harvest," she says, almost breathless with enthusiasm. "Indigo, woad, bedstraw, marigold, and yarrow." Burnett, who graduated from the University of Brighton in 2000, makes gorgeous tailored clothes embellished with buttons, frills, ribbons and geometric slashes of colour - as if a little girl had run amok in Savile Row. All her designs are handmade from organic fabrics and dyed with natural pigments - and will soon be coloured from plants grown outside her own back door.

Burnett is continuing a family tradition: her mother, Sarah Burnett, has used natural dyes to colour knitwear for the last 30 years. "Natural dyes are just beautiful," says Burnett. But there is another reason for her integrity - her aversion to the chemicals in synthetic dyes, particularly those used to create that most ubiquitous item of clothing, blue jeans.

The truth is that while large companies, such as Levi's, and designers, like Armani, have dipped a toe in the ethical market and are producing jeans made from organic cotton, most pairs of jeans - about a billion a year - are dyed using synthetic indigo. This is a substance created from benzene derivatives from petroleum, a fossil fuel that most of us realise is not in limitless supply. The benzene has to be treated with yet more chemicals, including hydrogen cyanide, to turn it into indigo dye. "It's a multi-step resource process, which is demanding on the environment and creates huge issues with waste," says Professor James Clarke, head of the Green Chemistry Network at York University.

Indigo does not naturally adhere to fabric, so has to undergo further processing using hydrosulphites to transform it into a dye. "These chemicals are particularly nasty for the environment," says Dr Richard Blackburn, head of the Green Chemistry Group at Leeds University. "Waste water containing these chemicals can affect ecosytems and can cause DNA damage to amphibians, for instance."

Thirty years ago, Dr David Hill, a biologist at the University of Bristol, vowed to come up with a solution to the problem of chemical dyes. His own father had grown dye plants since he was a schoolboy and Hill decided to see if he could turn a hobby into serious research that could eventually break the fashion industry's nasty chemical habit.

The dye indigo is derived from the plant indigo, but other plants also contain indoxyl, the precursor to indigo, too. These include woad, traditionally used as a war paint by Ancient Britons and Mel Gibson. Woad looks like scraggy spinach, but break one of its fleshy stems and it bleeds a tell-tale blue.

Hill began his experiments in his own garden and his allotment in Bristol, using a strain of woad originally cultivated by his father, who had found it growing wild by the river Severn. "I was initially unsure of what my colleagues at the university might think," says Hill, "so I analysed indigo production of my plants in my garden shed using bolognese sauce jars, filter funnels from Boots and milk bottles, rather than requesting lab facilities."

Hill eventually secured funding for his project and built up a series of partners across Europe. Finally, 30 years after he'd begun his research, he staged a fashion show of clothes dyed using the natural substances he'd grown. "My father would have been amused," he says.

Despite Hill's efforts, cultivating eco-friendly dyes on a large scale is tricky. One of the farmers who became involved in significant trials of woad was Ian Howard, but he soon realised that growing his own dye plants was going to be more difficult than the university lecturers had suggested. "The hard thing was taking woad from the lab to become a commercial enterprise. But by 2004 we had found a way of processing woad, which took minutes instead of hours. In the olden days one of the ways of extracting the indigo from woad was to use urine - Queen Elizabeth wouldn't have it anywhere near her because of the stench - but we found that we could use calcium hydroxide." Howard now turns the woad into indigo dye on his farm and sells it as a pigment, as well as using it to dye scarves, towels and sheets. Woad seeds are also used to make soap.

Although Howard's process creates a blue dye using green methods, even those companies that do use natural indigo on a large scale still employ harmful chemicals to turn it into a dye. To try to counter this, one of Hill's academic partners, Professor Philip John from Reading University, went back to medieval times to discover how woad was originally converted to indigo. By reading ancient manuscripts he discovered that dried woad leaves were fermented in a vat, and by recreating this process he found that a bacterium chemically changed the pigment in the woad leaves into indigo. "We discovered spores in thousand-year-old dye vat in a Viking excavation at Jorvik at York and revived them. We found that they were exactly the same as the ones we reproduced by following the recipes in the medieval manuscripts," he says. John is now trying to decipher exactly how the bacterium works and to create a green way of creating a commercially viable dye from woad. Meanwhile, a German company called DyStar has come up with a clean process using hydrogen gas, and a British company, led by Professor Tony Clifford from Leeds University, has developed a technique that relies on super-heated water. "There is an alternative now," insists Clifford's colleague, Richard Blackburn, "and in the long run it's cheaper because you don't have to pay for the environmental costs."

But if you want a green pair of blue jeans, there's virtually only one place to go in the UK. Mail-order company Howies will be producing one pair of very expensive jeans made from organic cotton dyed with natural indigo in its autumn collection.

Professor Hill, who still grows woad in his garden, says the plant could be used to dye all the jeans in Europe if someone with sufficient entrepreneurial skill and capital came along. "In the meantime, one way forward is niche marketing of indigo." And this is where people like Gracie Burnett, who shows her clothes at events across the country as well as making bespoke designer outfits, come in. At the start of next year, Gracie plans to launch a cheaper line that'll be available by mail order. And how romantic does that sound: a T-shirt dyed by hand from plants grown since medieval times freshly harvested from a garden in Dorset.