It's going to happen, it's just a matter of when.

Some business - most likely in retail, but possibly in transport - is going to announce it is using biofuel powered vehicles as part of its fleet and get a very nasty surprise.

A press release will be sent out talking up the vehicle's green credentials and spokespeople will be put forward to tell the world how the new vans or cars are just one example of the company's burgeoning green credentials.

At which point one of the world's most respected and recognisable environmental groups - most likely Greenpeace, but possible Friends of the Earth, WWF or Oxfam – will let loose their media attack dogs and go for the jugular.

"Why", they will ask across every media outlet that will give them airtime, "are you even bothering to trial a fuel that countless reports have proven does more harm than good?

"Aren't you aware your biofuel trial, however small, is contributing to food shortages and the rapid price inflation of basic staples which millions of people worldwide depend on for daily survival?

"Don't you know that the increased demand for agricultural land that is directly resulting from the rush to biofuels is leading to deforestation that accelerates climate change and increases the risk of extinction for many species, including those cuddly primates?"

They may even bring along a Brazilian farmer or wildlife reserve warden directly affected by the biofuel revolution to help  them make their point.

The firm, disorientated by the sudden assault on a strategy it thought would be universally applauded, will then put out some sort of statement to the effect that it is only sourcing its biofuels from sustainable sources.

To which the environmental campaigner will respond: "If you are using any form of conventional fuel crop, as opposed to waste crops or algae, then regardless of where it is being grown it is still taking up agricultural land that could be used for growing food at a time when world food stocks are dangerously stretched. The knock on impact of such biofuels is damaging, even if it is sourced from an otherwise 'sustainable farm' in the UK."

Sticking to its guns the firm may try to argue that the trial will deliver significant carbon savings compared to fossil fuels.

To which the campaigner - who is, by definition, far more familiar with these matters than the company's corporate PR department - will ask, "How can you be so sure? Have you included the emissions from the harvesting, processing and transport of the biofuels in your carbon calculations? How are you assessing whether farmers displaced by biofuel plantations aren't in turn contributing to deforestation? Are you following the recommendations of Nobel laureate Paul Crutzen and including the contribution of nitrogen fertilizers when working out biofuel's carbon footprint?"

Finally, the company will give up arguing the toss and try and remind people it is only a trial after all and the aim is to find out if there are any problems with the fuel.

To which the environmental group, by now joined by the entire green blogosphere and possibly even consumer groups, will say ,"why don't you just pull the plug now then? National Express did it and they know a thing or two about transport fuels. We need a moratorium on all biofuels based on fuel crops until genuine second generation fuels made from waste organic matter or algae are available.

"Until then, trials like this are almost certainly increasing carbon emissions, leading to loss of natural habitats and contributing to global food shortages."

Waitrose may have just managed to avoid just such a damaging confrontation - but only because its trial of rape seed oil powered vans is small in scale, its fuel is sourced from "sustainable" sites in the UK and Germany, the company has one of the best reputations for sustainability in the UK, and the environmental groups have not yet readied their anti-biofuel arsenal.

But there is every chance the next firm unveiling biofuel powered vehicles will not be so lucky, particularly if it is simply sourcing the fuel on the open market with no knowledge of where it originated.

If I was in the purchasing, marketing or sustainability department of any large company, I would be standing well back from any biofuel initiative, just in case it goes off in the company's face.