So, which is it: Saint or sinner?
Biofuels are a bit like the little girl in the nursery rhyme, they're either very, very good, or very, very bad - it just depends on who you talk to. Erik Jaques referees a heated and well-fuelled debate
It is being touted either as a vital milestone in the fight against climate change; a crucial component of long-term energy security - or as a totally wrong-headed acceleration toward Doomsday.
Back in 2006, when the EU launched its directive - which requires 10% of all member states' transport fuel to come from biofuels by 2020 - things were more clear cut.
Biofuels were seen as the perfect remedy for rising oil prices and planet-threatening emissions - renewable to a potentially infinite degree. They were also potentially carbon neutral through offsetting their eventual end-use by CO2 absorption during growth.
But a recent flurry of scientific reports, fraught polemical pugilism and cold, hard reality has undermined the illusory sense that biofuels were any kind of environmental panacea.
Most criticism is aimed squarely at the liquid fuel derivation of first-generation biofuels for transport and the motivating legislative drivers and the subsidies behind it. Other bio-energy family spinoffs, such as biogas (using emissions from landfill waste to generate electricity), are generally considered to have sound socio-environmental credentials.
In fact, many see the bio prefix as a misnomer when applied to mainstream bioethanol (produced by fermentation of sugar and starch crops and blended with petrol) and biodiesel (derived from oilseeds such as palm and rape for mixing with mineral diesel). A more accurate term, gradually coming into wider use, is agro-fuels - and this, it seems, is where the problems begin.
Among the more alarming observations to date is that many overly optimistic and speculative assessments have either overlooked or misjudged the amount of fossil fuels, land and water required for crop production as well as for transport of raw materials, processing, and export of the end product. Nobel prize winner Paul Crutzen noted that nitrous oxide emissions from nitrate fertilizers are 300 times more powerful than CO2 as a greenhouse gas.
There is mounting evidence that economic interest in biofuels has inspired some less than salubrious land-grabbing across the globe with all the negative impact that entails.
Then there's the alarming trend of rising food prices at a time of sharp worldwide deficits. Incredibly, spurred on by massive subsidies from the Bush administration, a third of all US maize crops were used to make ethanol. By 2025, the US hopes to replace 75% of all imported oils with biofuel.
This large-scale ramping up of the biofuel industry was instrumental in the 2007 United Nations' food price index rising by about 40%, following a 9% increase the year before.
Indeed, the UN's special rapporteur on food, Jean Ziegler, recently concluded that transforming wheat and maize into biofuels was "a crime against humanity".
The food-versus-fuel debate has even become a hot topic on Radio 4's national treasure The Archers.
In January, EU environment commissioner Stavros Dimas conceded, in an interview with the BBC, that "the environmental problems caused by biofuels and also the social problems are bigger than the EU thought they were".
It's a view reflected in a groundswell of support for a blanket moratorium on biofuel targets, lead by organisations such as the increasingly vociferous and influential voluntary organisation Biofuelswatch.
Reacting to the ideological sea change, the UK government cautiously ordered a Renewable Fuels Agency-led review of the economic and environmental damage caused by biofuels in February.
"Biofuels cannot be the solution to climate change on any substantial scale - that's clear," says Mark Lynas, environmentalist, journalist and best-selling author of Six Degrees: Our Future On A Hotter Planet.
"The UK and the EU have got it completely wrong. It strikes me as being completely bloody obvious as it has been fairly conclusively proven that biofuels actually increase emissions. They need to ditch all current targets."
Almuth Ernsting, director of Biofuelwatch, a volunteer-led campaign group, is equally emphatic. "We don't want a worse alternative. It's worse in terms of the land-grab involved, it's worse for the climate and it is a disaster for food security, which is already causing problems in the UK for people on low incomes, and a complete catastrophe for low-income countries.
"It would be nice to think the policy makers will turn round and say 'this method is bad for the climate ... so let's scrap it'.
"But we are speaking of a multi-billion dollar industry with masses of corporate lobbying, with masses of corporate interest. We are seeing business partnerships by the key industries that have not previously had partnerships, such as big oil and agriculture businesses, biotech-nologists and car manufacturers, venture capitalists. These people are clearly setting the agenda in Europe."
Barely in its infancy and shot through with holes, is it bad news all the way?
Giles Clarke, editor of Biofuels Review, which bills itself as a "primary news source for the biofuels industry", doesn't think so. "You're going to have a range in biofuels from excellent to completely awful, but to come up with a blanket 'we shouldn't do it' stance is Luddite in the extreme, it's people sticking their heads up their bums."
The relative efficiency of individual biofuels can differ wildly. For example, the Worldwatch Institute contends that reductions in greenhouse gases on a life-cycle assessment, resulting from ethanol produced in Brazil - as a part of its highly successful 29-year-old-programme - is about 80%, compared with just 10% from the US's maize-based ethanol.
For other biofuels proponents, current technologies are merely a transitory stepping stone to another, greener revolution.
"We need to be careful in how we describe biofuels," says Dr Martin Tangney, director of Napier University's biofuels research centre "The negative publicity stems largely from a percentage of the implementation of the first generation of biofuels and these are legitimate concerns but tend to overlook the second generation on the way."
As an expert in the biological production of the nascent biofuel butanol, Dr Tangney has already secured £500,000 in research funding to establish the centre as a neutral information portal for industry, government, academia and the public.
Opened in December 2007, Tangney says it was a direct response to a general knowledge gap on the subject. The remit of Tangney and his colleagues is resolutely on second-generation biofuels stemming from waste products that do no compete for food crops or land.
"Very often in this type of technology you get quantum jumps in productivity and process development and you can never tell when that's going to happen.
"Biofuels are one piece of the jigsaw puzzle to reduce energy consumption.
"We have an obligation to at least give it a chance to make it work."
One of the most promising second-generation developments in this respect is algae.
"The photosynthesising slimy matter can, according to the US Department of Energy, yield 30 times more energy per acre than many land crops due to their cellular structure, rapid reproduction rate and resilience under harsh growing environments.
Meanwhile, there are several less orthodox, commercially viable applications of biofuels currently on the market.
Argent Energy, which operates the UK's first large-scale biodiesel plant, can produce 50M litres of biodiesel a year, displacing 200,000 tonnes of carbon dioxide by recycling industry by-products such as tallow and used cooking oil.
It is currently involved in a six-month experiment with Stagecoach where passengers swap used cooking oil for discounted bus fares on eight vehicles.
In Scandinavia, an historically highly proficient region when it comes to environmental innovations, they have even managed to run trains on biogas extracted from rotting animal carcasses.
And what about UK-based Ecotec, which recently powered a truck all the way across the Sahara on chocolate waste?
"There's no one solution to all of this," says Graham Prince, communications director at D1 Oils, which is currently pioneering the large-scale growth of jatropha, a non-edible crop that can be grown on marginal land.
"The fact is the global economy runs on the internal combustion engine.
"Yes, there are legitimate concerns about the sustainability of biofuels, but I think they are here to stay. It is up to industry and government that they are produced sustainably and productively."
The UK government believes it is on the right track with the RTFO, which will require life-cycle assessments of the biofuels they have supplied in the hope customers will place a premium on sustainability.
"There's a natural level of scepticism about the science surrounding biofuels and until we actually get the reporting mechanisms in place we won't be able to reassure people," says Jim Fitzpatrick, parliamentary under secretary of state at the Department for Transport.
He states that the government is aiming to enforce mandatory sustainability targets by 2011.
To help remedy the problem on a wider scale, the Roundtable on Sustainable Biofuels - an international initiative bringing together farmers, companies, non-governmental organisations, experts, governments, and inter-governmental agencies - is currently working to achieve a global, multi-stakeholder consensus suppliers to provide on sustainable production criteria by June 2008.
"We recognise there are some weaknesses and deficiencies but equally we are very strongly of the belief that biofuels - which I think most commentators only a couple of years ago were saying were very positive - will be of great assistance in saving the planet."
Erik Jaques is a freelance journalist