Reefing the benefits

Even for climate change optimists, it sounds too good to be true: a liquid fuel made from plants that is chemically identical to crude oil but which does not contribute to climate change when it is burned or need swaths of agricultural land to produce.

But a company claims to have developed exactly that - a sustainable version of oil it calls 'green crude'.

Sapphire Energy uses single-celled organisms such as algae to produce a chemical mixture from which it is possible to extract fuels for cars or aircraft.

When burned the fuel releases into the air only the carbon dioxide absorbed by the algae during its growth, making the whole process carbon neutral.

Investors are already opening their chequebooks for the San Diego-based company. Sapphire has raised a total of $50 million in venture capital in recent months, the highest ever for an algae biotech company, including a significant investment from the UK's Wellcome Trust.

Algae are seen by many experts as promising a source of green fuel.

Ranging from single-celled organisms to large seaweeds, they are the world's most abundant form of plant life and, via photosynthesis, are extremely efficient at using sunlight and carbon dioxide from the air to make organic material such as sugars, proteins and, under the right conditions, oils.

Yusuf Chisti at Massey University in New Zealand estimates that algae could produce almost 100,000 litres of biodiesel a year per hectare of land, compared with 6,000 litres a hectare for oil palm, currently the most productive biofuel.

The money for Sapphire came flooding in after the company reached a milestone, refining high-octane gasoline from its green crude.

A Sapphire spokesman said: "The resulting fuel is completely compatible with current infrastructure, meaning absolutely no change to consumers' cars."

The fuel does not have contaminants such as sulphur, nitrogen and benzene which are contained in standard crude oil and the company believes the cost of its fuels will be comparable to standard fossil fuels.

Many biotech companies around the world are working on using algae to produce ethanol or biodiesels that could replace traditional transport fuels while avoiding the problems raised by traditional crop-based biofuels, such as displacing food crops.

Sapphire says that, with algae, there is no need to use valuable farmland to grow the basic resource.

"In fact the process uses non-arable land and non-potable (undrinkable) water and delivers 10 to 100 times more energy per acre than cropland biofuels," said the spokesman.

Where Sapphire departs from other algae companies is that its aim is not to produce standard biofuels such as ethanol or biodiesel. Instead, it takes its inspiration from the way crude oil was created millions of years ago.

"Way back when, when the algae were responsible for creating the long-chain hydrocarbons like diesels and heavy oils, the biomass just got buried and compressed and formed crude oil," said Steven Skill, a researcher in how algae can be used to make organic chemicals at Plymouth Marine Laboratory who is familiar with Sapphire's work.

Sapphire would not reveal details of the type of algae it is using, saying it will take the wraps off the technology in announcements in the coming months.

But Skill said the company is likely to be using genetically modified cyanobacteria, which used to be called blue-green algae. These organisms can grow quickly, doubling their mass in an hour, and can operate in high temperatures.

John Loughhead, executive director of the UK Energy Research Centre, said research on algae is a crucial part of the work to develop green energy sources in the future.

But he added: "I'd say it's a very sound idea but the question is, are they able to do anything practical in an efficient way?

"The key questions are the efficiency with which this process happens.

"They also have the classic renewables problem in that you're dealing with the ultimate energy source, the sun, which is quite diffuse, so you're only getting, in peak conditions, around 0.5 kw per square metre.

"You need vast, great big farms."

Algae can easily be grown in open ponds, but these result in very low-density blooms and are therefore an inefficient way to produce lots of fuel.

Skill said Sapphire would need photobioreactors to make a successful leap to commercial production, these are closed vessels which would provide plenty of light and carefully tuned conditions that could intensively grow the microorganisms.

Several teams around the world are testing designs for growing algae in them but none have so far made it to market.

Sapphire said it expects to be at a stage of commercial production of green crude within three to five years.

Geoffrey Love, head of venture capital at the Wellcome Trust, said the investment was made with this in mind.

Doug Parr, chief scientist at Greenpeace UK, said: "We urgently need to find ways of consigning the fossil fuel economy to history. Algae could offer promise, but to get a real grip on what this technology could offer we need far more information at our fingertips.

"The crucial requirement is that the end product can be produced in large quantities in a sustainable way, otherwise we're simply jumping out of the frying pan and into the fire."