Project Vesta is working to establish enhanced coastal weathering as a new negative emissions category with nearly limitless carbon dioxide removal (CDR) potential.
This project removes carbon dioxide from the atmosphere/oceans by utilizing enhanced weathering to turn CO2 into the carbonate molecules that corals use in their shells. This long-term carbon cycle is Earth’s natural process for removing the CO2 emitting by volcanoes. This process of chemical weathering of carbonate and silicate minerals has led to 99.9% of carbon on Earth to become stored in solid form as rocks and sediment, as exemplified by the White Cliffs of Dover.
At certain times in Earth’s geological history, tectonic forces have by chance exposed so much weatherable silicates and carbonates in the humid tropics around the equator, that the resulting weathering reactions removed enough CO2 that it led to global coolings and increased ice coverage at the poles. A growing body of research points to these “arc-continent collisions in the tropics set[ing] Earth’s climate state.”
Project Vesta takes inspiration from Earth’s natural biogeochemical mechanism for global scale carbon dioxide removal (CDR). However, because humanity does not have millions of years to wait for chance collisions of the right rocks to occur in the right places on Earth. Instead, we plan to combine and accelerate the steps of the process that result in the CO2 removal by directly exposing silicate rock in acidic ocean water.
The chemical reaction to “remove” and store CO2 is as follows: Atmospheric carbon dioxide (CO2) enters the surface ocean and dissolves in the seawater. Dissolved CO2 converts into carbonate ions (HCO3) and free protons (H+). This causes the pH to decrease, and can contribute to counteracting ocean acidification. The olivine dissolution reaction in turn consumes protons from the aqueous medium (Fig below). By consuming the protons, the olivine mineral matrix breaks down and releases metal ions (Magnesium, Mg) and silicate ions (H4SiO4) into solution. For every molecule of olivine dissolved, between 3 and 4 protons are removed from the seawater. By removing protons from the seawater in the dissolution reaction, the acidity (pH) decreases, while the alkalinity (acid buffering capacity) increases. This has been demonstrated under controlled lab conditions (Montserrat et al, 2017), and even in mesocosm setups (Montserrat et al, in progress). However, up until now, no projects have attempted to directly accelerate this process under natural (field) conditions.
Project Vesta’s plan is to efficiently accelerate the weathering reaction and CO2 removal aspect of the long term carbon cycle by placing the fastest weathering silicate, olivine, directly into warm, high-energy coastal environments. In the “beach application” scenario, olivine sand is mined from nearby reserves (within 300 KM) and distributed onto beaches and shallow subtidal areas. The dissolution of olivine particles in these shallow waters is greatly enhanced through wave action (stimulating grain collisions and surface abrasion) as well as through various forms of biological activity in the seabed. Such coastal olivine deployment could be advantageously integrated into various existing forms of coastal zone management (e.g. harbor construction works, sand nourishment on beaches, restoration of degraded coral fields).
Previous proposals for large-scale enhanced weathering on land or through open ocean alkalization are hamstrung by fundamental speed and efficiency flaws. On land, the olivine is stationary and a coating of silica builds up that dramatically slows the reaction. For ocean alkalization, the particles have to be small enough that they are able to weather before reaching the deep sea floor where it is cold and it will become stationary. To grind olivine to the micron level where it rapidly weathers is normally too energy intensive to make either of these processes viable, however, by utilizing the power of wave energy to finely mill coarse olivine from nearby reserves, our process is able to remain highly efficient. (See Question 7). As the underlying stoichiometric chemistry for the dissolution of 1 tonne of olivine resulting in up to 1.25 tonnes of CO2 is valid, the main question to demonstrate is whether wave motion and warm acidic water are able to significantly accelerate the weathering rate of olivine.
Table top shaker experiments have demonstrated that the forces of grain-on-grain collisions create fine fraction grains in relatively brief timescales and that motion is crucial in accelerating olivine dissolution. The above photo is of olivine grains after two months of shaking coarse grains sizes of 75% 1.4mm to 2.38 mm and 25% > 2.3 mm. After this short period of time, the grains are nearly all fine fraction of the size that weathers extremely rapidly.
A different table top shaker experiment containing 30 grams of olivine of material 50% 0.71-1.4 mm & 50% 2-5 mm grains, showed that after 12 days, 30% of the 30 grams had weathered to fine fraction less than 200 microns, with more than 50% of the fine fraction below 10 microns (pictured above).
The other major effect of motion on weathering rate is the effect of motion on surface abrasion. When olivine chemically weathers, the reaction causes a silica coating to quickly build up on the surface of the grains. In stationary applications, this coating significantly slows and can even inhibit the reaction. In the above “before” and “after” images, you can see how after 3 days, the 2-5 mm grains with the yellow dashed lines have been made smooth through collisions, this process also removes the silica coating on the surface (represented with the dashed yellow lines).
Flume experiments have quantified the effect of motion on olivine weathering and dissolution kinetics by putting the olivine in motion and measuring the change in pH as a proxy for the weathering reaction. In the above chart, broken lines represent times when the water was stopped. When the olivine is in motion and surface abrasion is occurring, the pH rapidly rises. When the water stops, as CO2 continues to enter the top of the flume, the pH drops back down. Once the motion begins again, the pH continues to rise. This demonstrates clearly that motion is essential to accelerating the olivine weathering reaction and also that the resulting reaction is able to deacidify the water as the olivine binds to the CO2 dissolved in it.
By accelerating Earth’s natural process of CO2 removal these and other experiments have demonstrated that enhancing the weathering reaction of olivine has the potential to remove global scale CO2 emissions, while helping to deacidify the ocean on human timescales.
However, due to the lack of proprietary technology with the underlying natural process and a limited negative emissions market, commercial investments in this field have been lacking. Further, the research institutions of the world have thus far failed to fund the pilot projects and demonstrations needed to bring this carbon dioxide removal technology to large scale deployment.
Project Vesta, a non-profit organization, was created to bridge this gap and carry out the projects needed to advance the science to a deployable and financeable level. Before large scale deployments for CDR can proceed, pilot projects are required to fully quantify the accelerated weathering rate in the real world and ensure the safety of the olivine weathering reaction to the marine environment. Our overall goal is to bring forward the entire category of enhanced coastal weathering on the technological readiness scale (Figure 1.7 above) and unlock the entire “enhanced weathering” category for global scale CDR.
For the last 10 years, enhanced coastal weathering has been stuck on Level 5, with a lack of funding for the large scale, real-world pilot projects required to demonstrate the actual weathering rate, safety, and life cycle efficiency of the process from quarry to beach to bicarbonate. Project Vesta is taking that first step to advance the enhanced weathering field with our Phase Ia Pilot Safety Study. While it is primarily designed to determine the safety of the release of precipitants from the reaction, the olivine on the beach will be weathering and is available for negative emissions credit purchases.
Before large-scale deployments can go forward, we must prove the safety of the process and verify the hypothesis that adding olivine to an existing ecosystem will not cause harm from any of the precipitants, including heavy metals such as nickel that can be contained in the crystal lattice of the olivine. Project Vesta’s lead scientists and partners include ecotoxicologists and some of the world’s top researchers on heavy metal release from olivine. Our partners at Deltares, a Dutch non-profit research consultancy for water, soil, and subsurface, have publicly released a model called PNEC-pro that is approved as a second-tier assessment for determining site-specific ecotoxicological risks to aquatic species based on the bioavailability of heavy metals.
The hypothesis of our expert panel is that while heavy metal may be released into the water, the heavy metals will quickly bind into forms that are not bioavailable to animals in the ecosystem. The existing models need to be adapted for ocean use and we will use our data to help optimize these open source models to generate one that can quantify a rate at which olivine can safely be added to the environment. Data gathered from research on the corals in the natural olivine beach in Hawaii, Papakōlea, has determined that the local corals and ecosystem are unaffected by the release of precipitants from olivine weathering. We are a “safety first” organization which is why we are testing safety before speed with our Phase I Pilots. We want to ensure that adding olivine to a new environment will not have a net-negative effect on the ecosystem (only on CO2).
The Phase Ia study will consist of two similar bays located in close proximity to each other, where one bay will serve as the control and the other as the experiment. Bays have been selected for this experiment because we want a slower refresh rate of the water so that precipitants can build up to higher levels than they normally would on an open coastline. This makes the data easier to attain and will give us a “worst” case scenario of precipitant buildup. The beaches selected for the project are located in the Caribbean in a currently publicly undisclosed location. We are working hand-in-hand with the local government to deploy the project. The beaches are remote, but we are working with the nearest villages to ensure their informed consent is attained and we are further working to hire their residents to help with security and eventually, the last-mile delivery of the olivine sand, and other partnerships. We have surveyed and sampled the bays and beaches, and they meet the requirements for our project. A further benefit is that there is a high-energy beach nearby (Northwest of the Control beach) where we could carry out the Phase Ib speed study soon thereafter.
The experimental setup and monitoring scheme will adhere to a Before-After Control-Impact (BACI) design. In this manner, any measured effects can be unequivocally attributed to the olivine application. We are deploying long term monitoring equipment to both bays to determine the baseline signal and to ensure the conformity of the characteristics of the two bays. Geochemical flux measurements are required to measure the olivine dissolution rate, to effectively convert it into carbon credits. Some proxies for measuring olivine dissolution are:
- Dissolved Silicate
- Dissolved Nickel
- Total Alkalinity (TA)
- Dissolved Inorganic Carbon (DIC)
Flux measurements of reaction products (above) over the sediment-water interface (SWI) are to be done both in situ and ex situ, by extracting sediment (with added olivine) from the system and incubating them in the lab.
The compartments of the ecosystem that need to be sampled are:
- Overlying water
- Sediment solid phase
- Sediment pore water
- Biota encountered in the ecosystem
Once sufficient data has been acquired, we will begin deploying a layer of olivine sand to the bay on the right (outlined in green above). All of the deployed olivine will be available for purchase as net-negative emissions credits and the rate at which they weather will be quantified in the experiment.
This Phase Ia Pilot is a key part of our plan to bring enhanced weathering in the coastal zone to the fore as an entirely new category of carbon dioxide removal with nearly limitless upscaling potential. To this end, a key deliverable from our Phase I Pilots will be a Coastal Enhanced Weathering Integrated Assessment Model (CEWIAM) that future enhanced weathering projects will be able to utilize. Based on a project’s specific inputs, the model combines the Life Cycle Assessment, Safety Data, and Weathering Rate, and returns a project-specific cost per tonne of CO2 removed per year. We plan to release this model to the world in an open-source way so that it can be verified by the science community and certified for net-negative emission purchases. The acceptance of the CEWIAM for CDR has the potential to spur the formation of a gigatonne scale market for enhanced weathering CDR projects.
Olivine is one of the most abundant minerals on Earth, making up over 50% of the upper mantle. A volume of less than 10 KM3 on 2% of the world’s shelf seas has the potential to offset all of humanity’s yearly CO2 emissions. Coastal enhanced olivine weathering is permanent, cheap, scaleable, and does not compete for arable land, fresh water, or other limited resources. It is future proofed against a worse climate because as the planet gets hotter and/or the oceans more acidic the weathering process speeds up. For these reasons and more we believe coastal enhanced weathering needs to be fully developed and deployed, and this pilot Project is the first step in taking this CDR technique from the lab to the beach, and eventually to the world.