Enhanced Weathering and Carbon Sequestration
In this era of concern about climate change, and with the accepted premise that traditional row crop agriculture is a significant contributor to the release of CO2 into the atmosphere, scientists are constantly looking for new technologies that will reduce the amount of soil-derived carbon [C] that is released from cropland acres. Scientists at the Univ. of Illinois Urbana-Champaign Institute for Sustainability, Energy, and Environment [iSEE], in cooperation with scientists from the Leverhulme Centre for Climate Change Mitigation in Sheffield, UK, have developed a new method to calculate the CO2-reduction potential of basalt rock amendments that may be added to cropland soils. Details of this process, known as “enhanced weathering”, are reported in an article titled “Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering”.
The research used to develop the technology was conducted at the Univ. of Illinois energy farm between 2016 and 2020. An article titled “Climate Win-Win: Enhanced Weathering” by iSEE Communications Specialist Julie Wurth provides summary points about the research and its meaning.
• Applying finely-ground basalt rock [formed from the rapid cooling of lava] to farm fields can capture significant amounts of CO2, and prevent it from being released to the surrounding atmosphere.
• With “enhanced weathering”, the rock is applied to cropland to capture C before it is released to the atmosphere. As the rock weathers, calcium and magnesium are released from it and react with dissolved CO2 in the soil to produce bicarbonate, which is harmlessly redirected to the groundwater.
• The research reported in the above-linked article reports results that quantify the weathering rate and CO2 reduction potential of the basalt rock that is applied as an amendment to soil.
• According to the authors of the study, the “basalt additions, by pumping inorganic C from the atmosphere to ground water, effectively offset up to 42% of C emissions from a maize/soybean cropping system, and when paired with conservation tillage or cover cropping, could turn this cropping system into a net C sink”.
• In addition to calcium and magnesium, basalt also contains phosphorus and minor nutrients that are released during weathering, and this could benefit soil fertility.
In an article by Beerling et al. titled “Enhanced weathering in the US corn belt delivers carbon removal with agronomic benefits“, the authors investigate how the weathering of basalt rock can be used as a carbon dioxide removal [CDR] mechanism when added to farmland soils in the U.S. Corn Belt. The following results from this research support the use of EW for determining the amount of CDR that can be accomplished by a basalt rock soil additive.
• These results show that the use of EW measurements can be part of a toolkit for quantifying rates of basalt weathering and time-integrated CDR.
• The results reported in this article also show that crushed basalt applied to U.S. Corn Belt soils drives long-term CDR under field conditions.
• Reported results quantified the agronomic benefits of EW that included increased crop yields in a corn-soybean rotation.
• The evidence reported supports EW with basalt as a promising management tool for measuring CDR in this major U.S. Corn Belt production system.
• Results from this research highlight the capability of EW as a tool to measure and facilitate factors that can improve soil health. These results are important to those producers who are seeking C credits that can qualify for the various carbon programs that are available.
Questions about using this product or other soil additives to sequester C in the soil are:
• What is the availability of the rock product used in this study? Are there suitable alternatives [e.g. biochar] if it is unavailable or if it is prohibitively expensive to use for the “enhanced weathering” purpose?
• What is the total cost of using it as a soil additive, including purchasing, shipping, and application?
• How much of the rock or a suitable substitute should be applied per acre to realize the maximum environmental and economic benefits?
There is no doubt that soil additives such as the crushed basalt used in the above studies will sequester C in the soil. However, the above questions must be answered before the results from this research or any research dealing with soil additives that can sequester C in the soil can be promoted as cost-effective ways of accomplishing CDR and/or improved soil health.
Composed by Larry G. Heatherly, July 2024, larryh91746@gmail.com