Alternative, Natural Carbon Capture: Olivine
Recently, it seems that artificial direct air capture mechanisms for carbon sequestration have received an uptick in media interest. While interesting engineering feats, they are often criticized for high levels of inefficiency (a significant amount of energy is needed to run them) as well as the fact that a concerningly high proportion of their initial backers and customers have been oil companies; either looking for a way to access cheap carbon for fracking and or to publically atone for their sins.
While this arrangement has received a mixed (and perhaps primarily negative) response from the sustainability community, it’s crucial to maintain support for carbon sequestration solutions.
As such, I thought it would be helpful to highlight a natural carbon capture solution that not only removes the opportunity to perpetuate the oil industry’s activities but potentially presents a more economically viable means of removing large amounts of atmospheric carbon.
The solution: accelerated olivine weathering.
Carbon cycle
Before humanity’s industrial age, carbon dioxide (CO2) was released through volcanic activity and absorbed through the weathering of volcanic rocks (calcium/magnesium silicates).
As Western nations developed mass-production methods, a significant and prolonged coterminous increase in output levels of CO2 threatened to minimize the natural limiting factor imposed by volcanic rock weathering. Today, CO2 emissions are more than forty times the natural, long-term removal rate via volcanic rock weathering.
This process of weathering is critical to combating climate change. Indeed, weathering is so powerful that it was a significant contributing factor to the last three ice-ages; specifically, the weathering of volcanic rock near the equator.
What is olivine?
The olive-green mineral, commonly known as the gemstone peridot, is one of the most abundant minerals in the earth’s crust. Large deposits are found near the surface of the planet. In fact, many existing mines have large incidental deposits of olivine, which sit unutilized in their vicinity.
While mining this olivine and storing it locally does serve to lower the overall CO2 footprint of these operations, said deposits could be deployed more effectively.
Where is it found?
As seen below, dunite massifs (an olivine-rich rock type) are located on every continent and near almost all high energy beaches most suitable for such deployment.
Large amounts of olivine already exist at operating mines
Why use olivine?
Olivine is one of the fastest weathering minerals that we have in significant quantities. Found in abundance in the earth’s mantle, this inexpensively acquired mineral is easily weathered in warm, high-energy tropical coastal regions.
When exposed to water and CO2, olivine turns CO2 into rock:
Mg2SiO4 +4CO2 +4H2O→2Mg2+ +4HCO3- +H4SiO4
olivine + carbon dioxide + water → magnesium + bicarbonate + silicic acid
In terms of capture capacity: 1 ton of olivine weathered results in 1.25 tons of CO2 sequestered.
Beyond carbon sequestration, the weathering reaction also yields an alkaline solution that de-acidifies seawater. This reaction simultaneously provides the materials for aquatic ecosystems, especially coral reefs, to recover and thrive.
Monetization
Carbon credits
Projects that permanently sequester carbon dioxide (and other greenhouse gases) can sell carbon credits to individuals and businesses attempting to offset emissions. The process requires specific standards to be met and final verification from a third-party organization such as Verra.
Through this process, one carbon credit represents one tonne of carbon dioxide permanently sequestered.
Carbon credit creation and issuance can be tokenized on Mantle to increase liquidity for project owners as the tokens can be sold through secondary markets to benefit from arbitrage opportunities.
Tax credits
Another path to monetization is to leverage the recent addition to the United States Tax Code, the 45Q credit. This credit provides up $50 per ton of carbon dioxide removed for sequestration unrelated to enhanced fossil fuel recovery.
Further, the minimum threshold for the type of projects eligible for the tax credits has been lowered substantially, from half a billion metric tons per annum to as little as 25,000 metric tons. This significantly reduces the threshold for the number of funds required to launch and begin monetizing olivine weathering operations.
The associated credits can either be monetized directly by the firm generating them or sold to other carbon dioxide emitting entities as an offset (as outlined in the previous section).
Deployment
The extensive geographical reach of olivine (dunite) deposits makes the mineral use for sequestration purposes more attractive than many other natural sequestration routes.
Transportation costs are also significantly lessened, as large amounts of olivine already exist at operating mines — and in some cases, in sizeable quantities. Additionally, the dunite fields’ widespread placement limits the maximum distance between any specific deposit and a suitable high energy coastline.
The physical deployment itself is considerably less complex than other sequestration methods, such as those involved in fossil fuel recovery. Ultimately, this means that the principal cost of olivine weathering is the acquisition of the raw mineral stock itself. Transportation and placement do not serve to expand the cost of olivine sequestration projects significantly, provided that each project takes advantage of nearby deposits and deploys the olivine in the method best suited for that particular geographical locale.
Further applications
Beyond the immediate application of carbon capture, the deployment of ground olivine has several other applications.
Biodiesel
Nourished by olivine weathering, diatoms (photosynthetic, eukaryotic microalgae), which are critical feedstock for oceanic ecosystems, are a good set of microorganisms for biofuels production.
Diatoms contain up to 50% lipids (molecules containing hydrocarbons), proliferate in the presence of silica (doubling their biomass in a few hours), and do not suffer many of the same issues faced by land-grown biofuel crops (opportunity costs with food production, irrigation, and fertilizer usage).
Forest fires
After the burning of fossil fuels, forest fires are the second largest contributor to global CO2 levels — under certain circumstances, carbon sinks can become carbon sources rapidly.
The use of serpentine powder slurries to combat forest fires is more effective than water alone. After these fires are controlled, the calcine powder reacts quickly with CO2 and water, offsetting a portion of the CO2 emitted during the fire.
Artificial land construction
The threat of rising sea levels, alongside increasing population levels, continues to drive the need for additional land near low-lying areas. This presents an opportunity to utilize olivine in the construction of artificial landmasses such as islands.
Not only do artificial installations provide for additional CO2 sequestration, but they also offer the other monetization channels through public and private financing that exists orthogonal to public monies provided for tax credits.
