At some time in the future, the production of oil and natural gas will come to an end, and Oman is therefore looking for alternatives to diversify its industrial base. The largest, but as yet barely touched natural commodity is olivine, as Oman’s major mountain chain is the world’s largest ophiolite complex. In the struggle against climate change proposals for direct injection of CO2 into the olivine rich rocks in Oman have already been published. CO2, together with water, will react with olivine and form stable carbonates. By this method large volumes of CO2 can be sustainably captured. The rate of reaction will increase in response to the release of the considerable heat of reaction, which will heat the rock. It is expected that this uneven heating may crack the rocks further, making them more accessible to fluid injection.The focus of this contribution will be on some possible ex situ uses, both in Oman and elsewhere. As our starting point was diversification of the industrial base, only applications with an economic perspective in the near or the far future are considered.
The Oman ophiolites bear spectacular evidence that they can capture CO2 without human intervention, but the rate of capture is insufficient to balance the huge amounts of CO2 that are pumped in the atmosphere by the burning of fossil fuels. This imbalance might be redressed if we find ways to increase the rate of reaction.
For all the olivine applications mentioned below, the prime driver is its capacity to weather faster than every other common silicate, capturing CO2 in the process. For any moderately humid climate, the most important weathering reaction is
(1) Mg2SiO4 + 4 CO2 + 4 H2O à 2 Mg2+ + 4 HCO3– + H4SiO4
In dry climates like in Oman, it is likely that the weathering reaction is more commonly
(2) 2 Mg2SiO4 + CO2 + 2 H2O à MgCO3 + Mg3Si2O5(OH)4
Whatever the climate-dependent weathering reaction, its final result is the sustainable capture of CO2
(3) 6 Fe2SiO4 + CO2 + 14 H2O à 6 H4SiO4 + CH4 + 4 Fe3O4
This way the addition of olivine powder can increase the production of green energy.
These last two applications, biogas production and biodiesel production would constitute a green follow-up for Oman’s oil and gas history.
Some plants are hyperaccumulators for nickel, and even when they grow on normal peridotites without any nickel mineralisation the Ni-content of their ashes may be 5% or more, making it a rich nickel ore. Clues have been found as to the determining factor for this property. This opens the exciting, but still distant possibility of growing salt tolerant plants on olivine beds in salt marshes, after the nickel hyperaccumulator factor has been implanted in transgenic halophytic plants. From the ash of these plants nickel can be recovered in an environmentally friendly and potentially economic way, while the olivine in which this nickel was incorporated is weathering quickly in warm salty water and captures CO2.
It is certainly not true that the olivine option to counteract climate change and ocean acidification can only earn money by carbon credits, once it is certified. Certification is complicated, because in several applications of the olivine option one can not always measure exactly the amount of CO2 that is captured. Fortunately for many other applications the effect can be measured quite well by comparing the compositions of ingoing and outgoing waters in systems where olivine is added. In reality, certification would likely progress in the same way that certification for emitting CO2 has progressed. In some cases emissions are directly measured, in many other cases emissions are sampled and modeled to an accepted standard. Regulatory developments would do well to track any developments in testing and demonstrating olivine applications; and there are many existing standards and processes that would be relevant for the above applications.
Olivine can become a major export product of Oman. The country has the largest olivine-rich rock massifs of the world. Its position along the Indian Ocean, and the possession of a modern port (Sohar) make the handling and shipping of olivine relatively simple. For applications within the country, one should look primarily for applications that require no fresh water. There are several such options, interestingly leading to biogas and biodiesel production, so in a sense a substitute for Oman’s present major economic base.
Olivine carries the promise to be the cheapest large-scale option to halt the rise of the CO2 levels of the atmosphere, and eventually reduce them if necessary. The pre-industrial CO2 level of 270 ppm is in no way a holy number to which we must return at all cost.