Explanation:

Second option is correct.

Volcano’s internal heat is harnessed to generate electricity and provide hot water for the city’s heating systems. Hellisheidi is not just an accomplished provider of green energy. It is also the site for a scientific breakthrough; an experiment to capture carbon dioxide (CO2) and turn it into stone – forever.

Called CarbFix, the project is pioneered by an international consortium led by Reykjavík Energy, the French National Centre for Scientific Research, the University of Iceland and Columbia University. It stands out among CCS experiments because the capture of carbon is said to be permanent – and fast.

The process starts with the capture of waste CO2 from the steam, which is then dissolved into large volumes of water. The fizzy liquid is then piped to the injection site where it is pumped 1,000m beneath the surface. In a matter of months, chemical reactions will solidify the CO2 into rock – thus preventing it from escaping back into the atmosphere for millions of years. However, this project is very water intensive. Over 25 tonnes of water per tonne of CO2 is needed.