Concrete application in enhanced weathering: Investigating the effect of concrete on barley and oat under field conditions

Weathering, the breakdown of rock into its elements, is a carbon sequestering process and a significant component of the Earth’s long-term carbon cycle. As rock is weathered, atmospheric CO₂ reacts with elements released, forming bicarbonates. These compounds are transported to the ocean where they are stored for thousands of years.

The above mechanism has garnered much attention in recent years for its use as a potential negative emissions technology to advance efforts in climate change mitigation. Enhanced weathering (EW) aims to accelerate carbon sequestering reactions of rock weathering by applying crushed rock onto vegetated surfaces. It’s also believed this practice could provide secondary benefits of improving crop yields and soil conditions. A variety of rocks, such as basalt and olivine, have been applied to different crops all over the world in an attempt to test their potential as a CO₂ removal technique and natural fertilizer.

This study aims to build upon previous attempts by employing a novel material, crushed concrete. Concrete is abundant in fast-weathering minerals such as portlandite and amorphous calcium silicates, making it an ideal candidate for EW. By harnessing the same bicarbonate forming and carbon sequestering reactions but using a waste by-product of the construction industry, the sustainability and circularity of EW technology could be further increased.

In this study, crushed concrete was applied to fields of oat (Avena sativa) and barley (Hordeum vulgare) in Co. Wexford, Ireland, during the spring growing season. Physiological (chlorophyll fluorescence and stomatal conductance) and morphological (dry mass and plant height) parameters were measured through multiple stages of the plant growth to assess the impact of concrete application on crop health and yield. Our results showed an increase in the dry mass (specifically seed dry mass) of barley, suggesting that barley may benefit from concrete application. No significant changes were observed in oat. Our results suggest that concrete does not negatively impact crop yields and could even improve yields in certain crop species.