DoNation: 'If 50 people give up bottled water, I will run a marathon'

To Hermione Taylor, it was a logical solution to a short-term problem. Due to embark on a sponsored cycle ride from London to Morocco, she found herself unwilling to nag friends for money. "It was the start of the credit crunch and a lot of people were students," she explains. "It felt like too much to ask." So she asked for something else: a promise. A promise to do a bit of good for the planet."We knew we wanted to do something for the environment – and, ultimately, that does not need money, it needs action."

The result was a list of 216 "pledges" from friends and family. They ranged from promising to eat less meat to washing clothes on a cool heat and, says Taylor, amounted to 16 tonnes of saved carbon (or, as she puts it "84 return flights to Morocco"). In the end, Taylor's grand cycle – which saw her sleep on beaches, stay with good samaritans and camp on hotel roofs – took 40 days. Its legacy has lasted much longer. Not only did she find that three-quarters of her sponsors continued their green actions after the allotted two months – but Taylor realised she had hit upon something potentially far bigger that a cycle race.

Having read for a masters in environmental technology at Imperial College London, she was only too familiar with the difficulty of encouraging green behaviour: "I'd focused on behavioural change and had looked at all sorts of so-called 'pledge schemes'. Talking to everyone when I got back, I realised that this ticked all the boxes for a good one."

Her idea was to take her pledge system and marry it with the online giving culture, pioneered by websites such as JustGiving, Virgin Money Giving and The Big Give. It's a field which, over the past decade, has expanded enormously – JustGiving, which handles some 85 per cent of all online donations – collected a staggering £188 million for charity in 2010 alone. The company has come in for criticism for its private, for-profit business model – unlike Virgin Money Giving, they deduct 5 per cent of every donation made and charities must pay £15 a month for membership – but Taylor points out the good they've done. "They've made giving so much easier – though I knew I'd have to be bit more innovative. For me, it was all about action, not donation." And so began a long year of planning, networking, researching and fund-raising, as Taylor attempted to turn her idea into a viable social enterprise. She was awarded two grants which paid for her cost of living. The rest she did alone – well, apart from the support of the social enterprise community and the help, since January, of an intern. Taylor had to turn her idea into a web-based reality, which meant acquiring knowledge of marketing, communications and design.

It's paid off. Earlier this month, thedonation.org.uk went live. Among those who've already signed up are Xavier Roeseler, who's hiking Spain's Camino Santiago, and Bojana Bajzalj and Will Usher, who plan to cycle from London to Ljubljana in 21 days. On signing up to the site, sponsors are given a choice of 20 actions that they can pledge to perform for a limited amount of time. Grouped into five categories – food, travel, energy, home and shopping – they range from giving up bottled water to installing solar panels. Make your selection, and you're met with a brief questionnaire to record your current habits and assess the change you will make. For every sponsor, an approximate carbon saving is worked out, allowing users to calculate their impact. "That's a big draw for people," explains Taylor of this. "The fact that there's a measurable benefit really makes a difference."

There is, of course, one potential flaw. Unlike websites where you pledge money, the DoNation can't hold everyone to account. It's perfectly possible – at least in theory – to pledge a bit of good behaviour and then default on it. This is something Taylor has thought long and hard about – and she believes she has a solution: "What we've done, essentially, is use a form of peer pressure. All the pledges are listed in public and, given that it's a friend or acquaintance that you are sponsoring, you're likely to be surrounded by people to police you."

It's with this in mind that I decide to give the system a go. Taylor counsels against opting for anything too ambitious – I don't have a bike, so cycling's out of the question. Equally, though, there's little point pledging something you already do. So no promise to take the stairs over the lift, or to wash on a low heat. Instead I decide to green my frequent trips to the kettle by promising to boil only the amount of water I'm going to use. And you know what? I've stuck to it (so far). It means waiting a fraction of the time that it would to boil a full kettle, too. Bonus! "A lot of people find that there are other positive repercussions," agrees Taylor. "It's not just about carbon."

Over the next year, she wants to expand the DoNation's capabilities, forming partnerships with companies, and expanding into a host of pledge-making activities. So far, most people who have signed up for the site have been doing some kind of sponsored race. Hopefully, the events will get more varied as time goes on – "We'd love to do a wedding list!" she says. Central to everything is a single simple message: behaving responsibly can be fun: "It can be a chore trying to be green. But we're making it social."