Secrets of Bath’s Roman Baths

The infamous algae growing in Bath’s Roman Baths could do more than make the water look green.

Researchers from the University of Bath believe the unique algae could one day be used to produce renewable biofuels.

Usually, algae grows at around 25°C but this limits the places in which it can be cultivated on a large scale. However, the algae in the Roman Baths are unique – they thrive at much higher temperatures.

Researchers have harvested different algae from the King’s Bath – which has a temperature of 46°C – and the Great Bath, which is at 39°C. The baths are kept at a steady temperature, fed by rain falling on the Mendip Hills. This water runs down limestone 10-14,000 feet underground where thermal temperatures can reach 100°C. Pressure builds up and pushes the water through the faults in the limestone, surfacing in the Roman Baths.

“We have identified seven different types of algae in the baths. There are many more but they are in such low cell densities that we have difficulty isolating them, for now,” said Holly Smith-Baedorf, a PhD student working on the project.

Each of the seven types of algae are being grown over a range of temperatures and are being compared to a control algae known for being good for producing biodiesel at normal temperatures.

“The results of this study will help us identify whether there is a particular algae species among the seven identified in the Roman Baths that is well adapted to growing at higher temperatures and also suitable for producing sufficient amounts of biodiesel to make wide-scale production viable.”

But algae’s use in biofuels is not just limited by temperature. Their walls can be hard to break, making extraction of oils energy intensive. The research team are therefore also looking for species with weaker cells wall and high oil content. The team will test the algae to determine which most suits the potential future mass growth for biodiesel production.