They might seem solid, but rocks gradually erode. Wind, rain, ice and snow all contribute to weathering; nibbling away at mountains, sea cliffs, limestone pavements and even solid granite tors.
Freshly exposed rock surfaces react with carbon dioxide in the atmosphere to make bicarbonate ions, which flow down to the ocean (hitching a ride on rivulets of rainwater) and are used by ocean critters to make limestone. This natural process helps to keep the Earth cool by removing carbon dioxide from the atmosphere and locking it up in rocks underground for a few million years.
So could we speed up this cooling process by smashing up more rocks? German scientists have been investigating the cooling potential of two types of rock: dunite and basalt. Their results, published in Environmental Research Letters, show that, if done on a large scale (comparable with today’s coal industry), crushed basalt could mop up nearly 10% of mankind’s carbon dioxide emissions every year, while dunite could absorb double that. Basalt could also have the co-benefit of adding nutrients to soil in tropical regions.
Pricewise, the technique would cost about 10 times as much as afforestation and about two to four times as much as carbon capture and storage.
