Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering

Authors: KANTOLA, ILSA - University Of Illinois; BLANC-BETES, ELENA - University Of Illinois; MASTERS, MICHAEL - University Of Illinois; CHANG, ELLIOT - Eion Corporation; MARKLEIN, ALISON - Eion Corporation; MOORE, CAITLIN - University Of Western Australia; VON HADEN, ADAM - University Of Illinois; Bernacchi, Carl; WOLF, ADAM - Eion Corporation; EPIHOV, DIMITAR - University Of Sheffield; BEERLING, DAVID - University Of Sheffield; DELUCIA, EVAN - University Of Illinois

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2023
Publication Date: 5/9/2023
Citation: Kantola, I., Blanc-Betes, E., Masters, M., Chang, E., Marklein, A., Moore, C., von Haden, A., Bernacchi, C.J., Wolf, A., Epihov, D., Beerling, D.J., DeLucia, E. 2023. Improved net carbon budgets in the US Midwest through direct measured impacts of enhanced weathering. Global Change Biology. 29(24):6829-7192. https://doi.org/10.1111/gcb.16903.
DOI: https://doi.org/10.1111/gcb.16903

Interpretive Summary: Climate change, primarily driven by excessive carbon dioxide (CO2) in our atmosphere, presents a significant global challenge. The situation is further complicated by traditional farming practices, such as maize/soybean rotation, which often exacerbate this issue by releasing more carbon than they store. Responding to this, scientists have developed an innovative strategy known as 'enhanced weathering' (EW). This method, which involves spreading magnesium or calcium-rich rock dust onto soil, was studied over four years in the Midwest US on maize/soybean and a plant called miscanthus. The results have been promising. The rock dust application significantly boosted the growth and overall production of both types of crops and, interestingly, also altered their carbon dynamics. In the case of the maize/soybean rotation, which typically loses more carbon to the atmosphere than it absorbs, EW helped offset this carbon loss by about 23-42%. Even more effective was the impact on the miscanthus plant, which naturally stores more carbon than it releases. Here, the EW technique contributed to a substantial increase in the amount of inorganic carbon stored in the system. This study shows how scientists have turned a major problem - carbon-releasing farming practices - into an accomplishment by developing and testing the EW method. By significantly improving the carbon storage capabilities of these farming systems, they have made a meaningful contribution to the fight against climate change. Thus, in the Midwest US, this strategy holds great promise for enhancing the sustainability of both conventional and bioenergy crops.

Technical Abstract: Terrestrial enhanced weathering (EW) through the application of Mg- or Ca-rich rock dust to soil is a negative emission technology with the potential to address impacts of climate change. The effectiveness of EW was tested over 4 years by spreading ground basalt on maize/soybean and miscanthus cropping systems in the Midwest US. The major elements of the carbon (C) budget were quantified through measurements of eddy covariance, soil carbon flux, and biomass. The movement of Mg and Ca to deep soil, released by weathering, balanced by a corresponding alkalinity flux, was used to measure the drawdown of CO2, where the release of cations from basalt was measured as the ratio of rare earth elements to base cations in the applied rock dust and in the surface soil. Basalt application stimulated peak biomass and net primary production in both cropping systems and caused a small but significant stimulation of soil respiration. Net ecosystem carbon balance (NECB) was strongly negative for maize/soybean (-199 to -453 g C m-2 y-1) indicating this system was losing C to the atmosphere. Average EW (102 g C m-2 y-1) offset C loss in the maize/soybean by 23-42%. NECB of miscanthus was positive (63 to 129 g C m-2 y-1), indicating C gain in the system, and EW greatly increased inorganic C storage by an additional 234 g C m-2 y-1. Our analysis indicates a co-deployment of a perennial biofuel crop (miscanthus) with EW leads to major wins – increased harvested yields by 29-42% with additional CDR of 8.6 t CO2 ha-1yr-1. EW applied to maize/soybean drives a CDR of 3.7 t CO2 ha-1yr-1 which partially offsets well established C losses from soil from this crop rotation. EW applied in the US Midwest creates measurable improvements to the carbon budgets perennial bioenergy crops and conventional row crops.