With traditional carbon sinks such as the Amazon rainforest facing an uncertain future, scientists are looking for creative efforts to slow the accumulation of carbon dioxide in the atmosphere. A new study at the University of Sheffield has proposed a technique known as “enhanced rock weathering” that enhances the soil’s ability to remove carbon dioxide from the atmosphere by spraying it with stone powder.
Like other geological engineering techniques, such as cloud seeding and machines that suck carbon from the air, enhanced rock weathering is a technique designed to reduce the amount of carbon dioxide in the atmosphere. Rocks naturally absorb carbon dioxide when decomposed in the environment, and enhanced rock weathering is one way to strengthen this process by first crushing the rock to increase its surface area and then adding dust to the soil to speed up the sequestration process.
The team at the University of Sheffield has completed what it says is a nation-by-country assessment that carbon dioxide reductions could be achieved if the technology were applied to the world’s farmlands. To do this, the researchers developed a model that takes into account the different carbon dioxide removal potential seisphons of countries and the costs involved.
The team’s analysis found that globally, enhanced rock weathering can absorb up to 2 billion tons of carbon dioxide from the air each year. That’s more than the global aviation and shipping industry emits more carbon dioxide and accounts for about half of Europe’s current emissions.
China, the United States and India, the world’s largest emitters of carbon dioxide, are the most promising countries, capable of removing 1 billion tons of carbon dioxide per year alone. The researchers say this could be achieved at a price comparable to other proposed CO2 removal strategies, at a cost of about $80 to $180 a tonne. The team says that while the carbon footprints of other countries such as Indonesia and Brazil are between 1/10 and 1/20 in the United States and China, their climate and vast arable land make them ideal for the task of removing carbon dioxide by enhancing rock weathering.
As for where the powdered rock comes from, the researchers recommend sourcing waste from various industries. For example, it may come from silicate rock dust left behind in mining operations, while silicate by-products from steel manufacturing can also be recycled for these purposes.
The most important thing, the researchers say, is that the technology won’t be too difficult to deploy, because in any case, farmers often use additives such as agricultural lime to treat their soil. The team called on governments to establish national stone powder lists and to encourage the use of stone powder in crops.
“In many agricultural areas around the world, the practice of sowing gravel to improve soil pH is common,” said study co-author Professor Steven Banwat, director of the Global Food and Environment Institute. “There are already technologies and infrastructure to adapt these practices to take advantage of basalt dust. This provides a potentially rapid transition to agricultural practices to help capture carbon dioxide on a large scale. “
The study was published in the journal Nature.