Ocean Alkalinity Enhancement – A preliminary research agenda and maturation roadmap

CarbonActionNow! is pleased to announce the publication of this white paper, which can be downloaded here.


Global anthropogenic CO2 emissions have continued to increase since the Paris Climate Agreement was adopted in 2015, lifting atmospheric CO2 concentration from a peak monthly average of 404 ppm in 2015 to 415 ppm in 2019. The continuing delay in leaving peak CO2 emissions in our wake increases the likely scale at which CO2 will have to be removed from the atmosphere, during this century and beyond, if the Paris goal of limiting warming to well below 2°C is to be achieved. Estimates of the scale of carbon dioxide removal (CDR) needed to meet the 2°C goal range from 100 to 1000 GtCO2 by 2100, with a removal rate potentially reaching 10 GtCO2/yr by 2050 and 20 GtCO2/y by 2100.

However, many of the technologies that will need to be deployed to reach this scale have made little progress beyond the laboratory bench. A 2019 US National Academies of Sciences, Engineering, and Medicine (NASEM) study sought to accelerate the maturation of these technologies by developing a research agenda addressing current knowledge gaps, as well as opportunities for cost reduction and other issues that could constrain deployment. Ocean-based approaches were beyond the scope of the NASEM study, posing the risk of delayed maturation in this area, and a reduction in the total CDR achievable by 2100.

This working paper follows the NASEM approach in establishing a preliminary research agenda for ocean alkalinity enhancement (OAE), and also outlines a technology maturation roadmap towards large-scale deployment. The two-fold aim of this work is, firstly, to focus R&D attention on knowledge gaps that must be closed to enable informed decisions on OAE demonstration and later deployment activity and, secondly, to identify the potential longer term, primarily non-technical barriers to impact scale OAE deployment that need to be addressed, in parallel with other early stage work, in order to provide the foundation for such deployment, if this is eventually undertaken.

UK Open Consultation on Carbon Emissions Tax

This UK Government open consultation sought comments on how, if introduced, the Carbon Emissions Tax would operate, and also on proposals for further development of the tax, including the possible inclusion of negative emissions.

CarbonActionNow! prepared a submission focusing on the negative emissions questions, which can be downloaded here.


Large scale deployment of carbon dioxide removal (CDR) methods to deliver negative emissions will be essential for the UK to meet its NDC commitment towards the Paris climate goals and will require the support of a wide ranging policy framework. However, linking negative emissions too quickly to policy mechanisms aimed at reducing emissions (e.g. the Carbon Emissions Tax or a UK ETS) would be problematic.

Targets, reporting, and markets for emissions reduction and for negative emissions should initially be kept strictly separate, and (dis)incentives should be designed to ensure the needed progress in both these areas.

Incentives to encourage the research, development and demonstration of promising CDR methods need to;

  • Keep options open
  • Ensure dependable support for demonstration projects
  • Demonstrate a clear pathway to commercialisation, and
  • Explicitly foster learning.

A number of complementary actions and policies are recommended to support of the UK’s overall net-zero objective, including;

  • Launching a Citizens’ Assembly to consider CDR deployment in the UK
  • Commissioning a strategic environmental assessment of CDR deployment in the UK
  • Commissioning a study on the integration of direct air capture into the UK energy system
  • Avoiding the labelling of specific sectors as “hard to abate”
  • Acknowledging and addressing the UK’s carbon debt
  • Increasing durable carbon utilisation, and
  • Introducing incentives for the use of low carbon fuels.

Negative Emissions Technology News Issue 2 now out


Microsoft’s ambition to become carbon neutral by 2030, announced in a recent blog post by company President, Brad Smith, will see the company investing in a portfolio of negative emission technologies (NETs) potentially including afforestation and reforestation, soil carbon sequestration, bioenergy with carbon capture and storage (BECCs), and direct air capture (DAC), as well as launching a new $1 billion climate innovation fund to accelerate the global development of carbon reduction, capture, and removal technologies.

The company’s CO2 removal (CDR) portfolio will initially focus on nature-based solutions, but will be reviewed annually, assessing the scalability, affordability, commercial availability, and verifiability of NETs, with the goal of shifting to more technology-based solutions before 2050, as they become more viable.

But what was most remarkable about the announcement was the commitment to also take responsibility for the company’s historical emissions – “to address our unpaid climate debt” – by removing from the atmosphere the total direct and indirect (Scope 1 and 2) CO2 emissions since Microsoft’s inception in 1975.

This to-date unique commitment puts the often discussed “moral hazard” posed by NETs in a new light. Against the concern that the unproven promise of NETs may discourage the needed deep and rapid reductions in GHG emissions must also be weighed the promise that NETs will give those corporations and individuals most responsible for historical emissions the opportunity to take similar corrective action – to address their own unpaid climate debts.

When – as is to be hoped – others follow this example of moral leadership, and also commit private sector finance to accelerate NET innovation and project development, we can look forward to a rapid maturation of the more technology-based solutions, reducing and ultimately removing the “hazard” caused by their current unproven status.

The current edition of NET News can be downloaded here, and covers key developments in this growing sector since our inaugural issue. We look forward to keeping you up-to-date with developments across the NET field – from R&D to policy and governance – in future issues.

If you wish to subscribe to future bi-monthly issues of NET News, please send us your details using the form below.

What’s with the deafening silence on Ocean Alkalinity Enhancement?

Ocean acidification has been prominent in the headlines this month, following the publication in December of a NOAA study that found the pH of surface waters in the California Current ecosystem have been dropping at a rate of 0.021 per decade during the last century, more than twice the global average [1].

This result is deduced from measurement of the shell thickness (actually the area normalized shell weight or ANSW) of Globigerina bulloides foraminifera samples recovered from radioisotope dated sediment cores taken in the Santa Barbara Basin. ANSW is related to the seawater carbonate ion concentration at the time the organisms grew, and from this, in turn, pH can be determined.

The Pacific coast of North America, from Alaska down to California, is home to a multi-billion dollar per year fishery and shellfish industry, which is already feeling the impact of acidification. The upwelling of low-pH, CO2-rich deep ocean waters into the California Current compounds the acidifying impact of anthropogenic CO2 uptake to create this double whammy for the industry.

Digging a bit deeper into local action plans, I was surprised to see that the main emphasis is on measuring and predicting the downward slide of ocean pH and the impact on ocean ecosystems, without much consideration being given to potential remedial actions that could be developed.

Through my work on negative emissions technologies (NETs) I have become familiar with the options to sustain and increase the ocean carbon sink – the sink that has come to our aid in absorbing close to one third of all historical CO2 emissions – and particularly the technique of ocean alkalinity enhancement or OAE [2]. One of the simplest approaches, proposed in 2008, is simply to disperse powdered limestone in upwelling regions [3] – including the region that is exacerbating acidification in the California Current!

So why was this not being discussed as a potential option to address the rapid acidification being experienced on the Pacific coast? Why the deafening silence? I posted the following query on the Ocean Acidification Information Exchange (OAIE) to see what the views of that community were.

It goes without saying that rapid decarbonization must be the foundation of our global response to the climate crisis, but even optimistic emissions reduction pathways lock in a lot of additional acidification over the next century and beyond.

Why aren’t we talking about progressing ocean alkalinity enhancement on a massive scale as a positive action to address this, starting regionally and extending globally? Whether it’s enhanced weathering of silicates, limestone weathering in upwelling regions, or the variety of electrochemically enhanced processes (including carbon negative fuel production) that can add alkalinity to the oceans, there are many techniques that could have a positive impact.

Yes, there’s a lot of research to be done, and, yes, it’s gonna come at a high cost (as will inaction.) But so far there seems to be a reluctance to even talk about the first steps that will begin this journey … let alone take them! Or have I missed something?

From the discussion that followed, I learned a lot about shell recycling, which has been investigated to increase alkalinity in estuarine waters subject to high freshwater runoff, where calcite/aragonite is undersaturated (one example being in Puget Sound). But the view on wider scale OAE was that older assessments that ruled out OAE as infeasible had done so by considering OAE as a sole alternative to emissions mitigation (e.g. [4]), rather than as part of a portfolio of techniques to supplement aggressive emissions reduction and, ultimately, enable us to reach net-negative.

So perhaps it’s time to get OAE back into the mainstream discussion – as a negative emissions technology with potentially billion dollar scale co-benefits. The recently approved US spending bill included for the first time an allocation for research into ocean capture, so perhaps we’ll soon start to see some progress.


[1] Osborne, E. B., Thunell, R. C., Gruber, N., Feely, R. A., & Benitez-Nelson, C. R. (2019). Decadal variability in twentieth-century ocean acidification in the California Current Ecosystem. Nature Geoscience, 1-7.
[2] Renforth, P., & Henderson, G. (2017). Assessing ocean alkalinity for carbon sequestration. Reviews of Geophysics, 55(3), 636-674.
[3] Harvey, L. D. D. (2008). Mitigating the atmospheric CO2 increase and ocean acidification by adding limestone powder to upwelling regions. Journal of Geophysical Research: Oceans, 113(C4).
[4] Can geoengineering solutions for climate change also help OA? in Frequently asked questions about ocean acidification (pg. 12). Available here.

Negative Emissions Technology News Inaugural issue

If we are to achieve the 1.5°C (or even 2°C) goal of the Paris Agreement, the next 30 years must see the growth of a new industrial ecosystem on the scale of today’s oil and gas sector but operating in reverse – not emitting CO2 but using a wide range of negative emissions methods and technologies to remove CO2 from the atmosphere.

The decade of the 2020s, must see peak global CO2 emissions left quickly in our wake, and the creation of a solid foundation for the rapid build-up of global CO2 removal (CDR) capacity.

The scope of this new ecosystem will be extremely broad – encompassing the upscaling of nature based solutions, such as afforestation & wetland habitat restoration; application of methods to enhance soil carbon stocks, such as conservation agricultural practices and biochar application; enhancement of natural geochemical processes, such as silicate & carbonate rock weathering; the capture and storage of CO2 from the combustion of short-rotation biomass; the application of chemical and electrochemical technologies to remove CO2 from ambient air, and many others.

Alongside the increasing awareness and application of nature-based solutions, the more technological sector of this nascent industry has started to move beyond the laboratory bench; pathfinding companies are gaining equity funding to finance pilot projects and cross-industry collaborations are emerging to de-risk and develop larger scale projects.

The challenge to bring CO2 removal to the needed scale – potentially 10 GtCO2/year by 2050 – is not purely or even primarily a technical one. National and international climate policies, including those relating to carbon pricing and trading, need to be put in place or adjusted to encourage rapid growth; international governance frame-works must be put in place to enable cross-border accounting and regulation of activities with regional and global impacts; public acceptance – the social license – must be nurtured through transparency, communication and public participation, starting early and building trust well before the technology demonstration and deployment stages.

The inaugural edition of NET News can be downoaded using this link. This issue covers key developments in this growing sector during late 2019 and the latest news for January 2020. We look forward to keeping you up-to-date on developments across the NET field – from R&D to policy and governance – in future issues.

If you wish to subscribe to future bi-monthly issues of NET News, please send us your details using the form below.