Soil may save our climate

California scientists win major grant to study how to decrease greenhouse gasses using soil amendments.

Whether it’s building giant solar farms, constructing public transportation or putting a price on carbon, most proposed solutions to global warming involve cutting carbon dioxide emissions. The California Collaborative on Climate Change Solutions, or C4S, is a group of researchers from UC Davis and other California universities who believe that reductions alone will not be enough to prevent the worst effects of climate change; they argue that humans must actively remove carbon dioxide from the air. On December 21st 2018, C4S won a 4.7 million dollar grant from the state of California to explore how soil amendments like compost, biochar and certain rocks can help pull carbon dioxide out of the air.

The current global warming crisis is caused by humans interrupting the natural balance between the carbon in the earth and in the atmosphere. Humans have rapidly released a large amount of earth-bound carbon by burning fossil fuels, the carbon remnants of living organisms that decomposed in soil long ago. The researchers at C4S want to use different methods to reverse the process and counter the rapid release of carbon dioxide by accelerating the earth’s ability to capture greenhouse gasses from the atmosphere.

“One of the ways to mitigate climate change is to increase the amount of carbon that is stored in the ground,” said Sanjai Parikh, an associate professor of soil chemistry at UC Davis.

The researchers will study how the addition of certain types of crushed rocks to soil can increase the amount of carbon that soil can store.

According to Benjamin Houlton, the director of the John Muir Institute at UC Davis, rock weathering has played an important role in controlling the amount of carbon dioxide in the atmosphere throughout earth’s history. In the early days of the planet, the level of carbon dioxide in the atmosphere was much higher than it is today. Rock weathering gradually led to a decrease in the amount of carbon in the air.

“CO2 is in the air, it goes into the water, when it dissolves in the water, it forms carbonic acid,” Houlton said. “That carbonic acid then starts to attack the rocks, break them down and that CO2 is now converted into things like carbonates which are another kind of rock, like limestone. That’s how the CO2 in the planet has come down over time.”

The best type of rocks for this process are silicate rocks. These silicate rocks actively pull carbon dioxide out of the air, but human activity is releasing carbon so quickly that climate buffers cannot work fast enough. Houlton and his fellow C4S researchers want to expedite the carbon sequestration action of silicate rocks by crushing them, increasing their surface area and adding them to soil. The researchers have found that the rocks also provide important minerals and nutrients that improve soil quality and increase crop yields.

Biochar, organic matter which is transformed into char under high heat, is another promising soil amendment. The char is a very stable form of organic carbon that can stay in the ground for extended periods of time and benefits soil.

In addition, Whendee Silver, a professor at UC Berkeley and a co-principal investigator on this latest grant, has shown some success using compost to help farms and rangelands retain and absorb carbon.

All of the potential soil amendments provide benefits to soil. These benefits are critical because they may make soil amendments a more feasible solution to remove greenhouse gases from the air. Many other ideas have been proposed, including man-made machines that directly capture carbon dioxide. However, there are concerns that these other methods are too expensive or that no one will pay for them. Soil amendments are cheaper to implement than many other carbon-capture ideas, and they may provide economic benefits by increasing the productivity of farmland, which could further offset the costs.

The C4S team will use the grant money and build on prior research to further demonstrate that soil amendments work and can be inexpensive enough to actually be used. The researchers plan to test the individual soil amendments and combine them together to study whether they can work together to provide added benefit.

Scientists involved in the project will use the new funds to set up test sites across California. Patty Oikawa, a professor at California State University, East Bay, is managing one of the test sites. Her team will use their portion of the funding to do research on the efficacy of using compost to turn rangelands into carbon sinks.  

“We plan to apply compost to three acres of rangeland on CSU East Bay’s Concord campus and monitor ecosystem-scale fluxes for three years,” Oikawa said.

Oikawa plans to monitor the site with special sensors that help determine whether an area of land is absorbing or releasing carbon dioxide. Her data from the East Bay test site, alongside the data from the other sites, will help paint a better picture of how effective these soil amendments can be. The project will last three years, and upon completion, the group hopes to demonstrate the feasibility of soil amendments in reducing carbon and providing benefits for farmers. For now, the C4S team is working quickly, because climate change is moving fast.

“No molecule of CO2 is unimportant right now,” Houlton said.

Written by: Peter Smith – science@theaggie.org