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A Praise for Basalt Potential: In situ mineral carbonation

Authored by Isabella Corpora, Research Fellow, Institute for Carbon Removal Law and Policy

Prepared for the Institute for Carbon Removal Law and Policy

A variety of igneous rocks and minerals are currently under evaluation as potential prospects to facilitate permanent carbon sequestration. Olivine, serpentine, and peridotite are some of the many that bind with carbon dioxide to form carbonates, hence providing a more permanent removal of captured carbon. This post is about a rock that deserves more attention: basalt.

Basalt is an igneous rock that is widely abundant globally and can bind to carbon dioxide more quickly than other options. Different forms of basalt stand as serious contenders for large-scale subsurface or in situ mineral carbonation, so why are they not a hotter topic in the carbon removal world? 

To set this up, there are distinct rocks used for removing versus storing carbon. Those evaluated to capture carbon can do so through the process of enhanced weathering. Enhanced weathering is usually completed on surface levels, such as with the mineral olivine that binds with ambient carbon dioxide along seashores. For storage purposes, rocks can be evaluated based on their presence in different layers below Earth’s crust. For both processes, the process of mineralization can occur where silicate materials and gases, like carbon dioxide, bind to form products like carbonates. Basalt is usually viewed for its storage potential. Carbon dioxide would need to first be captured through other technological processes and then injected into a basalt aquifer for carbonation. Though there is potential for basalt to be used for enhanced weathering purposes, the emphasis through this post will be on in situ storage.  

Changing atmospheric carbon dioxide into rocks is a complex chemistry trick. The ability of a rock to function as a carbon-storer is a function of surface porosity levels, gaseous pressure requirements, and temperature levels, among other factors. Some minerals, including wollastonite, tend to be less available in nature and have stricter requirements needed for successful carbonation to occur. Basalt, however, provides us a unique opportunity due to its scalability and characteristics as an igneous rock. Basalt forms from lava flows, notably along ridges in the ocean. These ridges span globally, making basalt the Earth’s most abundant bedrock and providing an occasion for further exploration and testing. It has a relatively higher porosity level (10-15%, compared to peridotite around 1%), allowing for larger amounts of carbon dioxide to bind in pores on its surface, and with a higher density in carbonate form can more easily fall to the ocean floor for storage.

More than 8% of Earth’s surface includes basalt, and Sanna et al. noted the ocean basaltic storage potential can be as high as 8238 gigatons available (at 2700m deep and with 200m of sediments forming a cap layer for trapping). This ocean storage is attractive because sedimentary layers in the deep sea would provide an additional natural permeability layer to maintain the carbon underground and decrease potential escapage, essentially acting as a “lid” to trap the carbon beneath it. Trapping is important because it helps prevent gas escapage while mineralization occurs. With other forms of rock, increased temperatures (think: energy requirements), higher carbon dioxide purification levels, and elevated pressures could all have stricter requirements for permanence below the Earth’s surface. This is an important consideration as proper storage can reduce the risk for escapage back into the atmosphere or ocean. 

It has recently been identified that mineralization rates in basalt are also much faster than previously anticipated. The CarbFix project near the Hellisheidi power plant in Iceland conducted a test study in 2012 and injected more than 175 tons of pure carbon dioxide into a basalt aquifer. The original expectation was for the mineralization process to take several years, yet the study found that carbonate material was formed in just two years, impressing scientists for the fast turnaround time and storage potential. The sequestration prices are also generally cheaper than have been seen with other mineralizaton options. In areas like Wallula, WA and near Hellisheidi, sequestration is being achieved at about $10-30 per ton of carbon sequestered. Though the price of deep storage in ocean basalt is higher, early estimates suggest that it can be achieved at $200 per ton. By contrast, serpentine, with higher pressure, temperature, and purification requirements, can range from $200-600 per ton sequestered.

As the Earth is now approaching 420ppm carbon dioxide in the atmosphere, the need for long-term carbon sequestration is becoming more pressing. Other forms of rock continue to stand as competitive contenders for carbon removal due to their quick binding rates with carbon dioxide and potential to be brought to areas where carbon removal is conducted, rather than transporting captured carbon to at times distant injection sites. Processes like enhanced weathering can also both capture and store carbon, uniting both goals and requiring less resources. Yet, many of these above-ground methods can have direct environmental impacts in ecosystems due to their surface exposure, such as with olivine. In situ basalt storage has few external impacts due to deep injections, quick mineralization rates, and natural trapping mechanisms.

A second CarbFix project has started and should provide additional findings on carbonation rates in basalt in the coming years. Perhaps with further usage of the CarbFix technology, we have a widely scalable solution on our hands. Other externalities of basalt should also be considered, but while greater investigation is being conducted, basalt seems to be a promising contender. It could be expected that we will see more basalt in our futures. 

References

Goldberg, David S, and Angela L Slagle. “A Global Assessment of Deep-Sea Basalt Sites for Carbon Sequestration.” Energy Procedia, vol. 1, no. 1, Feb. 2009, pp. 3675–3682., doi:10.1016/j.egypro.2009.02.165.

Goldberg, David S, et al. “Carbon Dioxide Sequestration in Deep-Sea Basalt.” Proceedings of the National Academy of Sciences, vol. 105, no. 29, 22 July 2008, pp. 9920–9925.,  doi:10.1073/pnas.0804397105. 

Matter, Juerg M, et al. “Rapid Carbon Mineralization for Permanent Disposal of Anthropogenic Carbon Dioxide Emissions.” Science, vol. 352, no. 6291, 10 June 2016, pp. 1312–1314., doi:10.1126/science.aad8132. 

National Academies of Sciences, Engineering, and Medicine. 2019. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: https://doi.org/10.17226/25259.

Sanna, Aimaro, et al. “A Review of Mineral Carbonation Technologies to Sequester CO2.” Chem. Soc. Rev., 2014, pp. 8049–8080., doi:10.1039/c4cs00035h. 

 

 

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Net-zero finance? An investor’s guide to a net-zero portfolio

Authored by David Morrow, Director of Research, Institute for Carbon Removal Law and Policy

Prepared for the Institute for Carbon Removal Law and Policy

It’s relatively clear what it would mean for a company like, say, FedEx to achieve net-zero carbon dioxide (CO2) emissions: it means that the company does not emit any more CO2 in a given year than it removes and sequesters in that year. There are some questions, of course, about exactly which emissions to count, but the basic idea is clear.

But what does it mean for banks, pension funds, and other financial institutions to achieve net-zero emissions, as a number of major banks have recently pledged to do? That’s the question that a group called the Institutional Investors Group on Climate Change (IIGCC) set out to answer through its Paris Aligned Investment Initiative (PAII).

Recently, PAII released it Net Zero Investment Framework, which PAII says “is designed to provide a basis on which a broad range of investors can make commitments to achieving net zero emissions and define strategies, measure alignment, and transition portfolios.” The Framework covers a lot of ground, as summarized in the table on page 8, but I want to focus on the role that carbon removal plays in the Framework.

In an appendix on “emissions accounting and offsets,” the Framework says:

As a general principle, investors should not use purchased offsets at the portfolio level to achieve emissions reduction targets. They should also adopt a precautionary approach when assessing assets’ alignment with net zero and the use of offsets. Recognising the finite availability of offsets from land use in particular, and the need to rapidly decarbonise all activities within sectors to the extent possible, investors should not allow the use of external offsets as a significant long-term strategy for achievement of decarbonisation goals by assets in their portfolios, except where there is no technologically or financially viable solution. The PAII will undertake further analysis in Phase II to assess the appropriate use of offsetting in specific sectors. Credits purchased by participants within regulated carbon markets that are designed to meet the net zero emissions goal can be used. 

Decarbonisation and avoided emissions should generally be treated separately. Similarly, investors should not offset emissions in one part of their portfolio through accounting for avoided emissions in another part. Given the necessity of effectively reaching zero emissions from investments over time, trading these two against each other is not consistent with creating incentives for investors and underlying assets to maximise their efforts to decarbonise their portfolios to the full extent possible.

There’s also a relevant line in the Framework’s “Paris Aligned Investment Initiative Net Zero Asset Owner Commitment” in Appendix C. Investors undertaking the commitment pledge to do a number of things, including:

Where offsets are necessary [because] there are no technologically and/or financially viable alternatives to eliminate emissions, investing in long-term carbon removals.

Overall, this seems like a sound approach that rightly prioritizes cutting emissions. Basically, it says that investors should avoid using offsets “except where there is no technologically or financially viable” way to cut emissions, and that they should not use avoided emissions as offsets. In other words, the Framework seems to be advising investors to view carbon removal as a last resort when decarbonization isn’t feasible, to prefer “long-term carbon removals” when offsetting is necessary, and to avoid investing in carbon removal themselves as a way to offset emissions from the companies they’ve invested in.

One thing to note is that the appendix text here doesn’t explicitly mention carbon removal, but it seems to use “offsets” to refer only to carbon removal, and not to avoided emissions. “Avoided emissions” are emissions that would have happened if someone hadn’t intervened by, for example, buying electric heat pumps for someone else to replace their gas-fired furnace. That sort of action isn’t carbon removal because it doesn’t physically remove carbon dioxide from the air; it only reduces the amount of carbon dioxide going into the air. The term “offsets” has sometimes been used to include both avoided emissions and actual carbon removal, so it would be helpful for the next iteration of the framework to clarify what they mean by “offset.”

With that distinction in mind, let’s break this down point by point:

    1. “Investors should not use purchased offsets at the portfolio level to achieve emissions reduction targets.” What does this mean? Suppose a pension fund invests in a retail company, and the retail company emits more CO2 than it removes. This principle is saying that, as a general rule, the pension fund should not buy offsets to counterbalance the emissions from the retail company. This is an interesting approach in that it puts the burden on the companies themselves, rather than the investors, to clean up their own emissions. If this were widely implemented, it would mean that companies looking for investors would have a strong incentive to achieve net-zero or even net-negative emissions.
    2. Investors “should also adopt a precautionary approach when assessing assets’ alignment with net zero and the use of offsets.” This is saying that investors should also be cautious when the companies they invest in say they are going to use offsets to reach net-zero emissions. Exactly what a “precautionary approach” looks like in this case isn’t spelled out, but at the very least, it means scrutinizing companies’ claims about offsets. Are their offsets actually removing as much carbon from the atmosphere as the companies claim? How permanently is the carbon sequestered?
    3. “Recognising the finite availability of offsets from land use in particular, and the need to rapidly decarbonise all activities within sectors to the extent possible, investors should not allow the use of external offsets as a significant long-term strategy for achievement of decarbonisation goals by assets in their portfolios, except where there is no technologically or financially viable solution.” In other words, don’t let companies rely on offsets as a big part of their long-term net-zero strategies, except when there is no “technologically or financially viable” alternative. The phrase “financially viable” leaves some wiggle room, but hopefully it will be spelled out in more detail through the “further analysis” the PAII is promising.  
    4. “Credits purchased by participants within regulated carbon markets that are designed to meet the net zero emissions goal can be used.” The charitable reading here is that investors should avoid wildcat offsetters who operate outside of well-regulated carbon markets, but “regulated carbon  markets” aren’t necessarily well regulated, so there’s work to be done here.
    5. “Decarbonisation and avoided emissions should generally be treated separately. Similarly, investors should not offset emissions in one part of their portfolio through accounting for avoided emissions in another part.” For example, if a bank is investing in a coal company and a wind energy company, it shouldn’t count the emissions avoided by the wind energy company as offsetting the emissions from the coal company. In other words, don’t do what financier Mark Carney tried to do recently.

As the Framework acknowledges, there’s a lot of work to be done to clarify the approach to offsetting and carbon removal, including how to determine whether cutting emissions is “financially viable,” what counts as a “regulated carbon market,” and how to determine whether a particular approach or project offers “long-term carbon removal.” The fundamental approach, though, rightly prioritizes cutting emissions and rightly emphasizes long-term carbon removal over avoided emissions in cases where offsetting is the only way to get to net-zero.