The process of drilling deep into the granite at the home of the world-renowned Biomes in Cornwall was finished in 2021, and Eden Geothermal Ltd (EGL) has now completed the heat main and plant and is ready to supply heat to the Eden Project and its new state-of-the-art nursery, Growing Point.

The well has a vertical depth of 4,871 metres, just over three miles.

Eden Geothermal switch on to heat the Eden site (Image: Mark Passmore)

The measured depth – the actual length of the well – is 5,277 metres (nearly 3.3 miles), making it the longest well under UK soil. The geothermal heat system is a single-well coaxial system. A 4000m vacuum-insulated tube has been inserted into the well, lifting hot water from deep below.

This is passed through a heat exchanger and the cooled water is then re-injected into the well via the outer ring.

The heat is delivered via a 3.8km heat main, at around 85 degrees Centigrade, which will supply Growing Point and Eden’s Biomes and offices.

To fund the research project, EGL secured £24 million in funding from a combination of the European Regional Development Fund, Cornwall Council and commercial funding from GCP Infrastructure Investments Limited, an investment trust advised by Gravis Capital Management Ltd.

The geothermal site (Image: Eden Project)

The Growing Point nursery has been built between the geothermal site and the Biomes.

It serves as a demonstrator of regenerative sustainability and a circular system in both its construction and operation, eliminating the need for a pre-existing off-site nursery, and reducing food miles and dependence on fossil fuels.

Sir Tim Smit KBE, Co-Founder of the Eden Project, said: "Geothermal is the sleeping giant of renewables: lying not under our noses, but literally under our feet. The Netherlands’ geothermal industry started with heating for greenhouses, and they are now aiming for it to contribute to a quarter of all their heating by 2050."

Eden Project Co-Founder Sir Tim Smit with Eden Geothermal Ltd CEO Gus Grand (Image: Mark Passmore)

Growing Point will enable Eden’s Living Landscapes Team to produce all the plants for the Rainforest Biome, Mediterranean Biome Outdoor Gardens and retail, as well as food for the hundreds of thousands of visitors Eden welcomes every year.

Rob Chatwin, Group CEO of the Eden Project, said: "We are developing new ways to grow and new ways to encourage people to think differently about plants and the planet.

"We have built a landmark sustainable nursery - a pillar of our wider ambitions for the future impact and expansion of the Eden Project - and it will help us accelerate massively our mission towards a climate positive future."