Nature’s filter: Dry Farmland’s Role in Sustainable Carbon Capture


In a recent field study conducted by scientists from the University of California, Davis, and Cornell University, it was discovered that drylands have the potential to capture carbon dioxide through enhanced rock weathering. The technique involves applying crushed volcanic rock to soil. Remarkably, this method has proven effective in arid regions like California, offering a potential solution for drought-prone areas. It is estimated that with this technique around 215 billion tons of carbon dioxide over 75 years could be captured worldwide.

In a recent field study, scientists from University of California, Davis, and Cornell University discovered that carbon can be restored in soil by applying crushed volcanic rock. And this technique has the potential to perform well in drought-prone areas too, like California. Named enhanced rock weathering, if implemented on a global scale, it could capture around 215 billion tons of carbon dioxide over 75 years. Due to its success in arid conditions, scientists are considering it suitable for drylands that are lately on rise due to climate change.

Researchers used crushed rock (metabasalt and olivine) on a 5-acre fallow cornfield in the Sacramento Valley. They measured and collected data during the winter of 2020-2021. This was a period of extreme drought in California, with rainfall recorded at only 41% of its historical average.

According to the study, plots with crushed rock were able to store 0.15 tons of carbon dioxide per hectare (2.47 acres) during the research period, surpassing the performance of plots without crushed rock. It is worth mentioning that different environments may have varying rates of weathering. Nevertheless, if this carbon removal rate could be replicated across all croplands in California, it would have the remarkable effect of removing 350,000 cars from the road every year.

Also See: Increasing Desert Potential by Engineering Carbon Sequestration

Understanding the process

Rain absorbs carbon dioxide from the air and combines with volcanic rock to store carbon. This process, known as rock weathering, is slow and cannot fully counteract global warming. However, crushing the rock into a fine dust accelerates rock weathering.

Lead author and doctoral candidate in soils and biogeochemistry in the Department of Land, Air and Water Resources at UC Davis, Iris Holzer said, “These reactions require water. Since we’re interested in the global carbon storage potential of enhanced weathering, we need to understand if it can work in these drier climates and if different measurement approaches are effective. We were excited to observe carbon removal in this environment.”

Holzer said, “We’re definitely seeing evidence of weathering processes taking place on short time scales. Even the infrequent heavy rains we get in the West might be enough to drive enhanced rock weathering and remove carbon dioxide.”

According to Holzer, the next challenge is to measure and verify carbon storage on larger scales and monitor it continuously.

Drylands have the potential to capture carbon dioxide and, as they cover forty-one percent of Earth’s land surface, are expanding as a result of climate change. In light of this, researchers emphasize the need to investigate enhanced rock weathering in these regions.

According to senior author Benjamin Z. Houlton, who is the Ronald P. Lynch Dean of the Cornell University College of Agriculture and Life Sciences, “We are facing a race against time in our efforts to curve global carbon emissions. However, there is hope. Our study has unlocked a new method for confirming carbon dioxide removal through enhanced weathering. This breakthrough is crucial for expanding the use of this technology in croplands around the world.”

Source: Direct evidence for atmospheric carbon dioxide removal via enhanced weathering in cropland soil

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