Understanding the potential for distributed carbon capture through (bio-)enhanced weathering

Abstract:

Chemical weathering of silicate minerals stabilizes Earth’s carbon cycle over long periods of time by trapping carbon in stable mineral form. One solution proposed for the distributed capture of anthropogenic CO₂ from the atmosphere is to speed up this natural process, by applying reactive minerals (ideally Ca- or Mg-silicates) to the land or ocean surface. The potential for such “accelerated” or “enhanced” weathering remains far from well understood, especially in the quantitative terms necessary to assess whether it could achieve significant negative carbon emissions. At the same time, relatively little attention has focused on how biological activity may be used to facilitate enhanced weathering, even though biologically-accelerated weathering is widely acknowledged to have been responsible for major changes in Earth’s environment in the geologic past.

This contribution will briefly review the state of knowledge about enhanced weathering in general and will present a range of possible approaches to “bio-enhanced weathering,” including by taking advantage of natural biological processes or through novel engineering. Detailed discussion will focus particularly on olivine, which is proposed as a model mineral for enhanced weathering because of its generally high reactivity. Ongoing experiments to quantify the dissolution rates of olivine, and their dependence on chemical equilibrium as well as the presence of organic ligands, will be discussed in the context of how mechanistic rate information can provide the necessary background knowledge for quantifying the potential of different (bio-)enhanced weathering proposals.