Weathering rocks for planetary scale carbon dioxide removal is not a novel idea, in fact, the weathering of silicates and carbonates in the long-term carbonate silicate cycle is how more than 99.9% of carbon on Earth has come to be stored in rock. This weathering cycle is Earth’s natural carbon dioxide removal (CDR) process, however, it normally takes millions of years to occur, so methods of “enhancing” or accelerating the weathering rate have been proposed.
A majority of the proposals for large scale CDR with enhanced weathering have looked at distributing olivine (the fastest weathering silicate) on land or in the open ocean. These proposals have generally not been implemented for large scale CDR though because the weathering rate of stationary olivine on land may be too slow, and in the open ocean, the particle sizes required for the olivine to weather completely before reaching the seafloor is too energy-intensive to efficiently mill.
To overcome these issues, the coastal environment of high-energy tropical beaches has been proposed as an optimal place to weather olivine rapidly with low energy use. The strategy of using beaches to accelerate the olivine weathering rate overcomes the typical impediments to feasibility by avoiding a potentially prohibitive energy penalty. The strategy is further kept efficient by minimizing the transport distance of the olivine, utilizing only quarries within a limited distance of the beaches.
Considering olivine is highly abundant, making up over 50% of the upper mantle, and each 1 tonne of olivine can remove up to 1.25 tonnes of CO2 from the atmosphere, there is theoretically enough olivine to remove total current yearly and historical anthropogenic emissions from the atmosphere. There is great potential to utilizing the weathering process to meet the negative emissions requirements of the majority of IPCC models that keep global warming below 1.5°C (2.7°F). However, aspects of the process that have been proposed, have yet to be tested. If enhanced coastal weathering is to be implemented on a large scale in the coming decades, research needs to be carried out on the weathering rate, efficiency, and safety of the process.
Prior research has used mathematical models of weathering rates, table top shakers, and flumes to measure the weathering rate under continuous motion with encouraging results, yet no real-world pilot project has been carried out to test for speed or the environmental effects on wildlife that the addition of large quantities of olivine might have.
The most pressing task in this field is to carry such an experiment on a pilot beach in the real world. This experiment will need to determine the olivine weathering rate on a real beach, as well as safety and other metrics that would be necessary to quantify prior to the large scale deployment of coastal enhanced olivine weathering. This poster lays out aspects of the experimental design and other processes that would go into deploying a pilot project so that coastal olivine weathering can finally go “from the lab to the beach.”
The experimental design and need for implementation discussed in this poster are not just theoretical, as Project Vesta and our associated scientists plan to actually deploy the proposed pilot experiment in 2020.
This poster was presented at the 2019 AGU100 Conference in San Francisco, CA. It was featured in the poster session “Marine Based Management of Atmospheric Carbon Dioxide and Ocean Acidification” convened by Greg H Rau, Matthew Eisaman, and Phil Renforth.
This poster and Project Vesta were featured in the SF Chronicle article “Could putting pebbles on beaches help solve climate change?” and on local Bay Area CBS and Fox TV affiliates.