basalt

Rock Dust And Carbon | Earth Wise

May 25, 2022 By EarthWise Leave a Comment

According to a new study by Cardiff University in the UK, Britain could achieve nearly half of the carbon removal needed to meet its climate goals by adding basalt rock dust to crop fields. The process is known as enhanced weathering and has been the subject of ongoing research in the U.S. at Cornell University and the University of California, as well as in the UK, Canada, and Australia.

Adding rock dust to agricultural lands speeds up the chemical reactions that lock up carbon in soil. Basalt contains magnesium, calcium, and silica, among other components. When basalt is pulverized and applied to soils, magnesium and calcium are released and dissolve in water as it moves through the soil. The minerals in the soil react with the water, and the carbon that would otherwise end up in the atmosphere instead forms bicarbonates, which can hang around in water for thousands of years. It can also eventually make its way to the oceans where it precipitates out as limestone and can stay on the seafloor for millions of years.

Basalt is a waste stream byproduct of mining and manufacturing and is found all over the world. Mining waste is the largest waste stream in the world, so there is no shortage.

According to the U.N. Intergovernmental Panel on Climate Change, applying rock dust to agricultural lands on a global basis could theoretically remove 2 to 4 billion tons of carbon dioxide from the air each year, which is between 34-68% of the global greenhouse gas emissions produced by agriculture annually.

The added rock dust would in fact be good for the soil and for crops. Whether the economics of producing and transporting it make sense remains to be determined.

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Adding Rock Dust to Farmland Could Get UK Almost Halfway to Its Carbon Removal Goal

Photo, posted April 24, 2011, courtesy of the State of Israel via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Turning CO2 Into Rock

January 6, 2020 By EarthWise Leave a Comment

As the world continues to struggle to find ways to reduce carbon emissions, there is increasing attention being paid to so-called negative emission technologies (NET), which remove and permanently sequester carbon dioxide from the atmosphere.

The University of Victoria in British Columbia has brought together an international team of experts to explore the possibilities of permanently and safely sequestering CO2 as rock beneath the ocean floor. The Solid Carbon Project seeks to extract carbon dioxide directly from the air and then, using deep-ocean technology powered by offshore solar and wind energy, inject it into sub-seafloor basalt, where it would mineralize into solid carbonate rock.

When CO2 is injected into porous basalt, a type of volcanic rock, it reacts relatively quickly with minerals to form solid carbonate, thereby permanently removing it from the atmosphere. Because 90% of the planet’s basalt is located beneath the ocean floor, the deep ocean is the place to do this kind of carbon sequestration.

The team includes experts in ocean science, carbon mineralization, renewable energy, engineering design, and oil-and-gas drilling/injection operations. Other experts are focusing on the social and legal implications of the NET technology.

Over the next four years, the Solid Carbon Project will assess the integration of multiple existing technologies that will be needed to successfully develop this kind of carbon storage. One of these is the direct air capture technology itself, which will need to be adapted to a renewable energy-powered offshore platform. The best outcome technologies explored by the project will be selected for a real-world demonstration at Ocean Networks Canada’s observatory site, 9,000 feet underwater in the Cascadia Basin, off the coast of British Columbia.

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A rock-solid solution for CO2

Photo courtesy of the University of Victoria.

Earth Wise is a production of WAMC Northeast Public Radio.

Growing Rocks To Store Carbon

April 24, 2019 By EarthWise Leave a Comment

The US Geological Survey recently published a comprehensive review of geological carbon storage in sedimentary rocks through carbon mineralization. That is the process by which carbon dioxide becomes a solid mineral, such as a form of carbonate. Certain rocks undergo a chemical reaction when exposed to carbon dioxide and turn into different minerals as a result.

The idea is to use carbon mineralization as a way to permanently store carbon dioxide that has been captured from power plant emissions, other industrial activities, or even directly from the atmosphere.

Two basic approaches are injecting the CO2 deep underground or exposing it to crushed rocks at the surface. The two types of rock best suited for mineralization through injection are basalt and various ultramafic rocks. Pilot studies have shown that injection into basalt can lead to mineralization in under two years.

Exposing carbon dioxide to crushed rock at the surface generally makes use of crushed mining waste. Mineralization can be much faster in this case because there is more surface area on the crushed rock where mineralization occurs. (However, the quantities of rock available at the surface are much less than what exists deep underground).

Like all carbon capture and storage approaches, the key consideration is cost. The USGS study estimates that underground injection would cost around $30 per metric ton of CO2. The crushed rock approach might only cost $8 per metric ton, but that assumes the crushed rock is already available. If it must be newly mined, the costs would obviously go up significantly. To put this into perspective, a typical car produces around 4 metric tons of CO2₂ per year. So, it would cost somewhere between $30 and $120 a year to eliminate the emissions from one car. Perhaps that is a price we need to pay until we ditch gasoline cars.

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