“Other rock types can also be used, but they are less effective or less available, although locally, there may be good reasons to use other rock types, such as basalts, anorthosites, or nepheline syenites. In the following weathering reactions, the formula of olivine will be simplified to Mg2SiO4 , although olivine normally is a mixed crystal of Mg2SiO4 and Fe2SiO 4 , with the Mg-endmember usually dominant.” The magnesium-rich end-member of the olivine solid solution series is called Forsterite and is found in large formations called dunite.
R.D. Schuiling, P148-149 – Geoengineering Responses to Climate Change
“The rate of weathering of dunite massifs in the tropical zone can be quantified, or at least a minimum rate of weathering can be firmly established. The first example is the dunite massif of Conakry/Guinea. This dunite occupies the entire peninsula on which Conakry, the capital of Guinea, is situated. It has an approximate length of 50 km and an average width of 5 km. Over its entire surface, it is covered by a thick lateritic weathering crust, which is very clearly visible as a purplish red area on satellite pictures (see Fig. 7.5). This lateritic crust, which is the iron-rich insoluble red residue of the dunite after deep tropical weathering, contains virtually no silica, magnesium or calcium oxides which were completely leached out during the weathering process . These components make up around 90% of the original dunite. This means that 1 m of laterite is equivalent to 10 m of dunite, or even more if the remaining components of the laterite were not completely immobile but have also been leached to some extent. The same author presents evidence that iron has in fact been fairly mobile and was partially leached out as well, which means that 1 m of laterite is equivalent to more than 10 m of dunite. The weathering crust has a thickness between 30 and 100 m. The age of the dunite (that is to say the time at which this dunite intrusion formed) has been determined as 195 million years. From these data, it is simple to calculate the minimum rate of weathering as follows: 50 m of laterite is equivalent to 500 m of dunite, 500 m (= 500 million microns) divided by 195 million years is 2.6 mm/year. This is already ten times faster than deduced from laboratory experiments, but the real rate of weathering must have been considerably faster. The rock is an intrusion. That means it was emplaced between rocks at some depth and covered by other rocks, which had to be removed first by erosion before the dunite became exposed and could start its weathering process. If the dunite intrusion has taken place at 2km depth, it would take 100 million years before the dunite massif was entirely laid bare by erosion at an estimated erosion rate of the order of 1–2 cm/1,000 years . This is the average erosion rate for all continents. This correction alone more than
doubles the calculated rate of weathering. That is not the only positive correction that must be made. In more recent times, the weathering process, under such a thick weathering crust, has virtually come to a standstill, as the thick laterite crust effectively shields the underlying rock from further interaction with the atmosphere. This shortens again the time span over which weathering was active, and thereby increases the rate of weathering.
-R.D. Schuiling, Geoengineering Responses to Climate Change P154
“A further positive correction concerns the difference between weathering of a solid rock as opposed to loose grains. A rock is attacked by weathering from above along a two-dimensional front, whereas loose olivine grains in soil are attacked from all sides. It seems certain that olivine grains in tropical soils dissolve at least at a rate of 10 mm/year, but most likely even faster. Even when their surface retreats only by 10 mm/year, a grain of 100 mm will disappear in 5 years. A similar calculation can be made for the dunite body at Jacupiranga, Brazil . Here, the rock has an age of 130 million years, and it is covered by a weathering crust of >40 m (this is where the drill hole stopped, but at 40 m, the drill was still in lateritic weathering crust). The minimum rate of weathering turns out to be >3.1 mm/year, but the same positive corrections have to be applied as in the Conakry case.”
-R.D. Schuiling, Geoengineering Responses to Climate Change P154
From a global balance of weathering and erosion, similar minimum rates of weathering emerge. The average rate of erosion of the continents is 1–2 cm in a 1,000 years . As olivine grains from the interior of the continents do not make it to the oceans, this means that olivine rocks dissolve (= weather) at least at the same speed, which is 10–20 mm/year.
-R.D. Schuiling, Geoengineering Responses to Climate Change P155
The most dramatic evidence for fast weathering of crushed magnesium silicate rocks comes from observations of weathering rates of mine dumps of such rocks . By measuring the amount of a suite of newly formed Mg carbonates, it was shown that the mine tailings of
two abandoned asbestos mines in British Columbia weather extremely fast. In this case, it does not involve fresh olivine, but its hydration product serpentine (Mg 3 Si 2 O 5 (OH) 4 ) that weathers and produces carbonates. This carbonation proceeds as follows:
Mg3Si2O5(OH)4 + 3CO2 + 2H2O —> 3MgCO3 + 2H4SiO4
At low temperatures, magnesite seldom forms, but in its place, hydrated magnesium carbonates, like nesquehonite Mg(HCO3)(OH)*2H2O, are found instead
In order to make sure that these carbonates have indeed newly formed, Carbon 14 analyses were performed on these carbonates which gave an age of about 0, showing that the carbon in these minerals really represents the sequestration of present-day atmospheric carbon . In one of the cases, the mine dump, occupying a surface area of 0.5 km 2 , had captured 82,000 t of CO 2 between 1978
and 2004, more than 50 times the maximum ever recorded for natural weathering under the most favorable conditions. The real rate of weathering is even higher because the authors have only taken the solid products into account, whereas the waters that percolate through the mine dumps carry an additional load of dissolved weathering products. These waters become quite alkaline, and their high silica content leads to small diatom blooms in a pool at the foot of the tailings dump and in at least one of the mine pit.
-R.D. Schuiling, Geoengineering Responses to Climate Change: Carbon Dioxide Sequestration, Weathering Approaches P155-156
“To understand what happens to olivine upon weathering we must distinguish between the chemical reaction of olivine with seawater and mechanical impacts during grain transport…The surf is clearly the world’s largest, most efficient and cheapest ball mill. The experiments also showed that a mixture of different grain sizes of olivine wears down more quickly than single grain sizes.”
-R.D. Schuiling, Geoengineering Responses to Climate Change: Carbon Dioxide Sequestration, Weathering Approaches P157-158
“In abiotic laboratory experiments, it was found that the surface of olivine grains retreats at a few tenths of a micron per year . This is described by the shrinking-sphere concept. Such low rates would make it difficult to use enhanced weathering to mitigate the greenhouse effect. Fortunately, there is observational evidence on rates of weathering of olivine in the real world (see below), which shows that the rates are more than tenfold, and probably 100-fold larger, than those found in the laboratory. Qualitative information on fast rates of weathering is obtained from volcanic terrains with rocks containing olivine. When volcanism started in the Eifel/Germany, synchronous Rhine sediments downstream in the Netherlands immediately started to contain a wealth of volcanic minerals, but no olivine, despite the fact that these volcanic rocks contain plenty of that mineral. Contrary to the there minerals of volcanic origin, olivine has not survived the short trip from Bonn to the Dutch border. Similar observations are reported from many other volcanic
terrains in the world. Although suggestive of fast weathering, this evidence is difficult to quantify.”
-R.D. Schuiling Geoengineering Responses to Climate Change p153
“In a recent experiment, this surf action was reproduced . Grains of olivine were rotated in conical flasks. Within 24 h, the crushed olivine grains that were originally angular, with a rough surface, had transformed into rounded and polished grains (Fig. 7.8).
The clear water at the start had become an opaque white suspension of very tiny olivine slivers, half of which had a grain size of less than 5 mm. The system reacts fast, the pH shoots up to 9.4, and a clay-type magnesium mineral is newly formed… The experiments also showed that a mixture of different grain sizes of olivine wears down more quickly than single grain sizes.”
-R.D. Schuiling, Geoengineering Responses to Climate Change: Carbon Dioxide Sequestration, Weathering Approaches P157-158
“The mechanical action, the grinding down of olivine grains, by waves and currents largely determines the rate of weathering of olivine on beaches and in shallow seas with strong bottom currents. The papers in which the rate of weathering of olivine grains on beaches is calculated , are based on theoretical modeling and overlooks the mechanical consequences of the surf, where grains are wearing down by the constant rubbing and bumping against each other.”
-R.D. Schuiling, Geoengineering Responses to Climate Change: Carbon Dioxide Sequestration, Weathering Approaches P157
How Much Olivine Is Needed For Total Yearly CO2 Emission Removal, What Size, and How Would It Be Distributed?
7 km^3 volume of olivine rock would be crushed and milled to grains of around 100 mm in diameter. If 7 km^3 is spread over an area of 10 million km^2, it will occupy a layer of 0.7-mm thickness. Grains of olivine of 100 mm will weather in approximately 5 years in tropical soils. It will, therefore, be cheaper to spread a layer of 3.5-mm thickness each year over an area of 2 million km^2, shift to the next area in the following year, and come back to the first after 5 years.
Project Vesta Logistics Questions
For details on the costs of mining and milling olivine pricing, see this model for a 5000 tonne per day mine of porphyritic (volcanic rock just like olivine), where the price per ton is $7.32. Considering the US his high labor costs and olivine is located all over the world, it would make sense that this is near the highest price we can expect to see. Olivine reserves are available fairly cheap and found near the surface. As the demand for olivine is currently pretty low as it is almost solely utilized in blast furnaces, by increasing demand, we can bring the price down further, and by foregoing profits, we can pass those savings along so each dollar can acquire more olivine, and in turn remove more CO2 from the atmosphere. When adding transport costs (hopefully low CO2 impact rail or boat), we are looking at a ~$10 per ton of CO2 sequestered…
The Life Cycle Analysis (LCA) of the release of CO2 from mining, milling, and transport of olivine creates an approximately 4-6% loss on CO2 removed. We will always work to minimize the transport distance from the source of olivine, and utilize low impact transit such as rail and boats. Further, many tons of olivine are already mined because the deposits are found above other valuable minerals, such as diamonds (found in a rock formation called Kimberlite). Utilizing these piles of waste rock, known in the industry as tailings piles, will allow us to harvest olivine without causing a significant CO2 output. Further, the dust from mining itself can contribute to the offset of the entire mine, as well as the very ground where the olivine is exposed. It starts weathering right away, and many ultramafic mineral mines, abandoned or active, eventually offset their own footprint and even go towards negative emissions. On of our olivine weathering rate sources is actually these tailings piles. See these studies:
“A major part of the olivine operation will involve cost-effective, low-impact transport and spreading of olivine over land or shallow sea. This is the reason why a maximum distance of 300 km from the mine site to the point of use is recommended. Classically one would think of trucks transporting the olivine inland, where it will be distributed either as grains by machinery that also spreads fertilizer, or as slurries mixed with pesticides. However transport by truck will significantly contribute to the cost, so one should also make good use of location-specific opportunities. In cases like Guinea, rail transport inland offers a good possibility, as two railroads for bauxite transport from the interior pass close by the likely location for a future olivine mine. The empty trains can carry loads of olivine inland on their return from the port at the tip of the peninsula. Most of the new olivine mines will be in the wet tropics. This means that they will often be situated in an area rich in rivers and creeks. It may be possible, then, to load barge- type boats with olivine, mount a pump on each boat and spray the passing river banks with an olivine slurry. The boats could also be used to transport loads of olivine more cost-effectively than by truck. If olivine is transported by barge-boats, transport distances are less critical than with trucks.”
Okay, that sounds good, but how about going into the actual economics and logistics of a project that could offset even just 5% of global yearly CO2?
Open pit mining; 5.000 tonnes/day US$ 7.32 / metric ton (less when upscaled); based on western U.S. mining operations (US Open Pit Mining Cost Model)
Transport: (self-discharging megacarriers; up to 400,000 ton)
Loading and unloading of a 200,000 megacarrier ~ 2 x 4-5 days = 10 days
Speed 15.4 knots (28.5 km/h; 17.7 mph) ~ 650 km/day
Travel ~ 2000 km; 2 x (outbound and inbound) = 4000 km = 6 days
Cost of 200,000 ton megacarrier order of US$ 40,000.- / day
Loading-travel-unloading-and-back 16 days (less, due to partial unloading underway)
16 days x USS 40,000.- = US$ 640,000.-
US$ 640,000.- / 200,000 ton = US$ 3.2 /ton
Total costs US$ 10.- to US$ 11.- per ton olivine (captures 1.25 ton CO2)
Yes, olivine is safe for humans and aminals on the beach. There are naturally occuring green sand beaches around the world, with the most popular one being on the main island of Hawaii and is known as Papakōlea or Mahana beach. All of the the olivine beach pictures found on our website were taken there. Wildlife there thrives, and we have further examples of human-made test beaches. You can see some kids playing at one in the Netherlands below:
Olivine is the most abundant mineral on Earth, making up more than 50% of the upper mantle. Right now however, there is not huge demand, so many of reserves of high-purity olivine in large formations known at dunite, are sitting idle and unmined. By stimulating demand, it is possible there would be a short term increase in price, however basic economics tells us, that since there is no limitation on the supply, as demand increases, it will increase the supply that is brought to market and further push the price down it settles at a new equilbrium. Our goal is to push the price down as low as possible to the limitation of the costs of mining, milling, and transportation (approx < $10/ton).
So even if the economics are favorable, is it possible to excavate the total volume of rock each year to offset all of humanity's CO2 output?
Yes, it is possible. Remember the equation for CO2 removed per ton of olivine weathered is as follows: 1 ton olivine weathered = 1.25 tons of CO2 removed.
We currently put out a significant amount of CO2 per year, so we need a volume of 7 km^3 of rock.
The equivalent amount of hydrocarbons acquired each year is currently greater than a volume of 10 km^3.
If the demand is there the economics and logistics are possible. For example, last year in Norway 3.4 million tonnes of olivine were mined by just 225 employees. To scale up mining for the entire world’s CO2 to be offset (7 km^3 volume), it would only take 1 to 1.5million people to get involved in open-pit mining. There are 3-5 million mining coal in China alone. That is ∼0.2‰ of mankind, which is not a lot at all. It is actually less people than are currently employed in the coal mining and oil industry. It’s about priorities…
We love trees and suggest we plant as many of them as possible, but the problem with using them as a means of carbon sequestration is that you have to protect them for 50+ years from pests, fire etc. If the trees were to burn, all of that carbon you worked so hard to sequester would be released, so it is not foolproof and decades of sequestration can be rolled back in hours. Whereas once the olivine grains are on the beach, the CO2 will eventually end up going into the seafloor in an irreversible chemical reaction (until potential subduction then volcanic activity in millions/billions of years)…
One of the breakdown products in the reaction is silicate, which is a limiting factor for diatoms. Diatoms are particularly hit hard by climate change and are important in the base of the food chain. Diatoms provide food for the entire ecosystem from fish and birds. Diatoms themselves may also actually be responsible for moving significant amounts of biomass to the deep ocean as they sink (further reducing CO2). They also compete with dinoflagellates, which are the cause of red tides and could be useful in stemming their increased occurrence by counterbalancing their rapidly increasing populations. And as for the magnesium, if we were to offset 100% of the next 100 years of anthropogenic CO2 emissions with olivine, it would only change the Mg-concentration of the ocean from something like 1296 to 1296.8 ppm and the bicarbonate content from 42 to 45 ppm. These changes are considered within the normal range of ocean water. We are mindful of olivine sources that could be tainted with iron or other heavy metals and will test the rock and water to prevent this potential problem before it would arise.
The average US person is responsible for putting out approximately 16.5 tons of CO2 (2014 World Bank). As for your individual carbon profile, there are many calculators out there that can help you decide how much to offset. For an in-depth calculation that you’ll need to pull out your electricity bills for, check the Resurgence one: https://www.resurgence.org/resources/carbon-calculator.html This one is good as well https://www.carbonfootprint.com/calculator.aspx And you can always find activity specific ones, such as how to calculate cryptocurrency offsets: http://www.cleancoins.io
Once that is added up you would be able to purchase your CO2 equivalent output in olivine with this formula (CO2 output in tons)/1.25 (quantity of carbon sequestered per ton of olivine), which we would then multiply by our strike price of olivine at that time.
Our plan is to fund the fixed costs of the beach and operations through larger scale donations and sponsorships so that 100% of your money goes directly to tons of olivine on the beach (and potential labor+materials if you purchased olivine jewelery) and not to administrative fees.
Every single continent has large olivine reserves that occur in 90% purity, a formation known as dunite. While there are single open pit mines with an excavated volumes of over 25 km^3, it would be more optimal to have 20-30 smaller mines that are within 300 km of the beach deposit site. Larger mines, of greater than 100 million tons per year, would have optimal economics to push the price down, but it can still be effective with smaller mines.