Insights from several hundred soil EC sensors and several thousand water analyses in three long-term weathering experiments

Are you curious about innovative ways to combat climate change using enhanced weathering (EW)? Our latest research dives deep into the potential of using electrical conductivity (EC), either in the soil pore water or in leachate water, measured manually or with EC sensors to monitor EW, a promising method for carbon dioxide removal (CDR). By accelerating the natural weathering process of rock dust on croplands, EW aims to capture atmospheric CO₂ and transport it to the ocean, effectively reducing greenhouse gases. But can we rely on such a simple and cheap way of measuring through EC to track this process effectively?

Over the past three years, we conducted extensive experiments involving hundreds of low-cost soil EC sensors and thousands of water analyses across different settings: a field in Fürth, Germany, a farm in Larissa, Greece, and a greenhouse with diverse soil and rock combinations. Our goal was to determine if these EC data could accurately reflect the changes in leachate alkalinity, a key indicator of CDR success. The findings were mixed; while some correlations were observed, the reliability of the sensors varied significantly across different conditions. Along the way we describe how we assess the success of EW experiments using accumulated total alkalinity.

Despite various challenges (and failures), our study reveals valuable insights and paves the way for future research. If you're passionate about climate solutions and intrigued by the potential of innovative technologies in environmental monitoring, delve into our detailed findings. Download the full paper below to explore the complexities and possibilities of using soil EC sensors in EW projects and learn how this could shape the future of carbon tracking.

Abstract

This paper investigates the potential of using soil electrical conductivity (EC) sensors and leachate EC measurements to monitor carbon dioxide removal (CDR) through enhanced weathering (EW). Using an extensive data set from three long-term weathering experiments (4,200 leachate lab analyses and over 1 million sensor measurements over a time span of 2 years), we find that while EC and alkalinity concentration data can qualitatively indicate CDR, they are not sufficient for quantitative assessments without leachate volume data or other methods to assess water flow. The results suggest that more accurate sensors or supplementary methods are needed to reliably monitor CDR in EW projects via EC, although EC data could help reduce monitoring costs when used as a proxy for TA alongside leachate lab analysis.

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Download the document (PDF, 30 pages, 105 graphs, 21 MB)

DOI: http://dx.doi.org/10.13140/RG.2.2.11415.79521

Update October 2024

After reading this blog post please also look at our blog article Why measuring alkalinity is not the same as quantifying HCO₃⁻ (How to avoid confusion about the seemingly straightforward use of alkalinity to quantify CO₂2 removal).