The race is on to find a renewable liquid fuel as oil prices skyrocket and global resources deplete.

Biodiesel can be produced by extracting the oil from the cells of certain types of algae, but limitations currently prevent the technology being used on a large scale.

Researchers from the University of Bath have found a potentially rich source of algae in the city’s Roman Baths that could make the production of biodiesel from algae commercially viable.

Adapting to higher temperatures

Algae cells are usually happiest growing at temperatures around 25°C and that can limit the places in which they can be cultivated on a large scale. But areas where these conditions exist usually make good arable land, so are needed for food production.

Ideally, it would be possible to grow algae in desert areas where there are huge expanses of land that don’t have other uses, but temperatures in these zones are too high for most algae to flourish.

Fortunately, algae cells are very versatile and can change many of their characteristics in response to their environment. The protected environment in the Roman Baths provides a perfect place for adaptation to higher temperatures to take place.

Selecting the right species

Researchers investigated seven different types of algae in the baths. There are many more but they are in such low cell densities that the team has had difficulty isolating them.

The research team is growing each of the seven over a range of temperatures and comparing them to 'control' algae known for being good for producing biodiesel at normal temperatures.

However, while the ability to grow at high temperatures is one limitation on large-scale biodiesel production, it is not the only restraint.

Algae cell walls are particularly difficult to break, making extraction of the oil inside an energy intensive process. Some algae cells are also easier to filter than others. Easier filtering greatly reduces the energy and economic cost of harvesting the algae from cultures.

So, as well as high temperature resistance, the research team are also looking for a species of algae with a weaker cell wall, high oil content and the possibility to use cheap filtration techniques to keep production costs low.

Wide-scale production

The results of this study will help identify whether there is a particular algae species among the seven that is suitable for producing sufficient amounts of biodiesel in high temperature locations.

By studying the unique algae growing in the high temperature waters of the city’s Roman Baths, the research team hopes to make the wide-scale production of biofuels a real possibility.

Bath's Roman Baths

There are two different baths. Both maintain a steady temperature.

The King's Bath is 46˚ celsius and the Great Bath is 39˚ celsius - both have remained constant for many years.

The temperature of the Roman Baths is created by rain falling in the Mendip Hills, and running down through limestone at 10,000 - 14,000 feet below ground where thermal temperatures can reach nearly 100˚ celsius.

Pressure builds up and pushes the water up through faults in the limestone, surfacing at approximately 250,000 gallons a day in the Roman Baths.