A new study published in Geology concluded that an extinct volcano off the coast of Portugal could store up to 1.2 to 8.6 gigatons of carbon dioxide, the equivalent of about 24 to 125 years of the country's industrial emissions. For context, in 2022, 42.6 megatons (0.0426 gigatons) of carbon dioxide were removed from the atmosphere by international carbon capture and storage efforts, according to the Global CCS Institute. A new study suggests that carbon capture and storage in submarine volcanoes at sea could be a promising new direction for removing and storing much larger volumes of greenhouse gases from the atmosphere. "We know that most countries, including Portugal, are making efforts to decarbonize the economy and our human activities, it's news that this can be one of the tools to solve the problem," says Ricardo Pereira, a geologist at the NOVA School of Science and Technology and co-author studies. The deposition of carbon dioxide in an extinct volcano would relied on a process known as “in situ mineral carbonization'. In this process, carbon dioxide reacts with elements in certain types of rocks to form new minerals that store carbon dioxide safely and permanently. Elements such as calcium, magnesium and iron combine with carbon dioxide to form the minerals calcite, dolomite and magnesite. Rocks that contain large amounts of calcium, iron and magnesium are ideal candidates for this process – such as the volcanic basalts that make up most of the sea floor. Scientists knew this and focused on a coastal volcano for several reasons – the structure of the volcano could provide an ideal architecture for carbon injection and storage, the rocks are the right type for the reactions involved, and the location is not too close to a large population, but not too far either. (Laura Fattaruso, Geological Society of America, PHYSORG)