Obvious examples include the generators producing electricity needed to drive lighting and sound systems, as well as the trucks bringing everything from stages and scaffolding to toilets and drinking water onto a festival site.

But by far the most damaging activity in terms of carbon emissions is simply people travelling to and from events.

With UK festivals set to attract more than one million visitors this year, people's journeys - be it by car or train, bus or plane - make up about two-thirds of the greenhouse gas output linked to the UK festival scene, according to Julie's Bicycle.

And this issue of audience travel is "one of the hardest areas to address because it is outside the festival operator's immediate control", says Ms Tickell.

Most festivals are held on greenfield sites, meaning they do not lie conveniently on public transport routes.

Promoters often use incentives to encourage audiences to think carefully about how they travel. But some, such as running free or subsidised shuttle buses from train stations - have a cost.

And besides, for many the convenience of the car is too appealing, especially for families or those unable to resist the potential of bringing a few extra cans of lager or tins of beans to the campsite. This, say organisers, can make promoting alternatives a tough sell.

Measuring impact

Last week ten big-name festivals - including the Big Chill, and Lovebox - pledged to cut 10% of their emissions during 2010.

And Mr Benn believes that improving environmental performance "no longer just makes environmental sense, it makes economic sense as well".

The rising cost of sending waste to landfill (the tax alone is £40 a tonne, set to increase to £72 by 2013) is just one factor organisers are all too well aware of.

Therefore reducing waste and increasing recycling is important to a festival's financial as well as environmental sustainability, says Claire O'Neill of A Greener Festival - which accredits festivals based on their environmental performance.

She says UK events such as Bestival are taking inspiration from a scheme launched at the Vuuv festival in Germany - which charges every attendee five euros and gives them a bag to fill with either waste or recyclables. The money is returned when they bring back a full bag.

"Incentivising your audience and involving them in clearing up and recycling helps reduce waste" Ms O'Neill says. "And you also encourage people to think about waste separation, and hopefully that's something that they take back home with them."

While admiring such initiatives, Ms Tickell of Julie's Bicycle argues that the best thing event organisers can do is to try to measure their energy impact.

Such a "volatile" environment as a temporary site in a field makes this tricky, she acknowledges, but is heartened that more festivals are doing it.

"People are starting to measure their energy profiles - not for the audience, not for the artists but in order to commit to reducing it," she says.

"It sounds boring, but this is very much the first stage towards making a seismic cultural shift."

Local support

Going carbon-neutral is an ambition of Benedict Addis - the sustainability manager at Standon Calling - a festival for about 4,000 people set in the idyllic grounds of a Hertfordshire manor house.

However, Mr Addis admits it would be cheaper to use so-called red diesel, which is designated for use in things such as tractors, boats and generators - and is sold at a preferential tax rate.

"We're only able to afford bio-diesel thanks to the support of our local supplier and even then we pay a premium for it," he says.

"But it's a big step forward in becoming carbon neutral."

Unexpected benefit

However, not all its green initiatives cost the festival money.

An on-site bore hole has been used to plumb in glass-washing machines. Rather than handing out disposable plastic glasses, its bars now serve drinks in tough, reusable, polycarbon glasses.

"Last year we only used about 2,000 glasses for a festival of 4,000 people," Mr Addis says.

"Before we did this we were getting through something like 20,000 disposable ones."

And because the glasses now used are considerably more expensive to buy, drinkers pay a 50 pence returnable deposit.

"But a lot of people, especially after they've had a few pints, don't bring them back," Mr Addis says.

"So that unclaimed deposit money pretty much covers the cost of the plumbing."

'Prettiest girls'

Another money-saver has been forcing on-site traders to serve food and drinks with plates, cups and cutlery made from corn starch.

Along with food waste - these are taken to a local farmer for composting. Within two months the compost is used on the land where the festival is held, and sold to other farmers to cover costs.

But not all issues require such complicated approaches.

A common problem at UK festivals is tents, camping chairs and barbecues being abandoned at the end of a festival by people too partied-out (or, possibly just lazy) to pack away what are increasingly seen as disposable items.

However, Mr Addis says he has hit on a novel approach.

"On the final day of the festival it's not unknown to ask the prettiest girls working in the rubbish collection team to go around the campsite, encouraging people to take everything home with them," Mr Addis laughs.

"And this will often do the trick."