Autonomous Upwelling for Carbon Dioxide Removal Application
Since 2005, the team at Ocean-based Climate Solutions and its parent company, Atmocean, have pioneered making ocean upwelling/downwelling practical and low cost. Our objective with the following content is to provide a scientific basis and technical explanation for autonomous upwelling (also known as artificial upwelling) as a carbon dioxide removal (CDR) application.
In reviewing possible risks of conducting autonomous upwelling, Professor Andreas Oschlies from GEOMAR says the following: “There is essentially no environmental risk associated with small-scale field trials. For hypothetical large-scale deployment, local oxygenation of subsurface waters by translocation of surface waters and deeper waters will be accompanied with a translocation of nutrients and heat, likely leading to a cooling and enhanced biological productivity of surface waters. Enhanced productivity will eventually be followed by enhanced respiration and oxygen consumption that may to some extent offset the initial oxygen gain. Enhanced biological productivity will likely enhance the productivity of higher trophic levels including fish. There will be shifts in the ecosystem, the valuation of which is difficult, but with higher productivity in normally not over-productive waters, these will most likely be viewed positively. It cannot be ruled out that species of little commercial value or possibly even toxic algae may benefit more than others. Mechanisms of such ecological shifts are poorly understood and based on current knowledge there is little expectation that shifts will differ from natural shifts observed when moving from oligotrophic to more eutrophic conditions, such as usually found further onshore.”
On this page we aim to describe the science and implementation behind our technology and cover the following topics:
- Physical footprint: our solution takes advantage of carbon, less constrained by arable land.
- Capacity: our technology has a path forward to being a meaningful part of any carbon removal solution (i.e., more than 0.5GT CO2/year by 2040).
- Cost is less than US$ 100/ton of CO2 removed by 2040.
- Durable: meaning it stores carbon permanently (more than 1,000 years).
- Verifiable: we use scientifically rigorous and transparent methods for monitoring and verification of CO2 sequestered.
- Additionality: new net carbon being removed rather than taking credit for removal that would have occurred regardless.
- Safety and compliance: we are legally compliant, responsibly, and actively engaging with the public to determine and mitigate possible risks and negative externalities.
- Net-negative Lifecycle: overall, our Autonomous Upwelling system results in a net reduction in atmospheric CO2
Technical explanation of Autonomous Upwelling
Carbon fixation through plant production in the ocean is driven by vertical mixing of nutrient-enriched deep water into sunlit surface layers –achieving net carbon fixation above baseline and net carbon sequestration (CO2 “offsets”). Ocean gyres, particularly the North Pacific gyre, are areas with relatively low vertical mixing and strong vertical nutrient gradients. Horizontal spatial coherence is very high in these gyres, so measuring impacts of pumped upwelling are simplified. The vast gyre areas where conditions are similar suggest scalability of wave-driven pumped upwelling is substantially driven by the number and size of pumps deployed.
The key to producing net carbon sequestration in these low-nutrient, low-chlorophyll (LNLC) ocean gyres are the upwelling of deep waters containing nutrient concentrations greater than the dissolved CO2 concentration plant stoichiometry basis, i.e., the Redfield ratio.
In a 2008 paper, David Karl and Ricardo Letelier calculated the net sequestration potential from pump-driven upwelling using data collected at the long-term monitoring Station ALOHA in the North Pacific gyre near Hawaii. They calculated that upwelling of waters from 200 m or deeper provides excess phosphate, which triggers a sequence of nitrate and then phosphate uptake drove blooms of phytoplankton. The secondary phosphate bloom fixes more dissolved CO2 than is upwelled, resulting in net CO2 sequestration. Using the Karl-Letelier calculations, we build our pumps with the intake at 500 m to maximize the carbon fixed per unit area relative to the vertical length of the pump.
In 2007, we conducted a sea trial of a 0.75m diameter by 152m deep upwelling pump to determine the upwelling flow rate, which was substantially identical to our current design except for dimensions. With triaxial accelerometers on the valve flappers recording open/close cycles, and temperature sensors top and bottom, we determined the time for deep cold water to surface. The outlet temperature sensor showed cold water arriving at 08:45:00, about 15 minutes after the first upwelling stroke. Dividing tube volume by elapsed time gives a flow rate of 0.078 m3/s.
Low-Nutrient, Low-Chlorophyll (LNLC) Ocean Gyres & Beyond EEZ Boundaries
The initial location will be in the open ocean, approximately 200nm from Oahu, Hawaii. The initial scale will be ten pumps spaced 720m apart (equal to two per square kilometer diagonally).
This location affords access to long-term baseline data from Hawaii Ocean Time Series (HOTS). The HOTS far-field data allows for robustly embedding the data from the pumping volume within a scientifically rigorous time-series data set, which allows for a better understanding of the uncertainty in the carbon sequestration calculations.
Sequestration beyond the terrestrial biosphere
Autonomous upwelling in the LNLC central gyres uses an area of the world with relatively low impacts from other human endeavors, and hence net CO2 sequestration through pump deployments has little secondary impacts.
Scale-up, Seasonality, and Additionality.
In the central gyres, horizontal scales are vast, i.e., on the order of 100’s to 1000’s of kilometers, while vertical scales are compact, 10’s to 100’s of meters. Vertical mixing, therefore, potentially generates significant impact with relatively small energy inputs. Furthermore, scalability is minimally constrained. While each float’s impact is spatially constrained to a few square kilometers, the systemic float program’s effectiveness is not limited until a vast number of floats have been deployed. See the “Scaleup” section on page 15 to calculate the scaling necessary to drive the sequestration offsets using autonomous upwelling pumps to greater than 0.5 gigatons CO2 per year.
In the NPSG and other LNLC gyres, productivity is limited by nutrient scarcity – so all-new production from pumped upwelling is “additional.”
There is a slight latitudinal limitation within the NPSG LNLC area as sunlight is adequate through the entire year to drive phytoplankton blooms at least 30° N.
Permanence & Verifiability
Mean ocean age is over 1,000 year’s old.
In the North Pacific, the mean ocean age is over 1,000 years, thus qualifying our outcomes from this region as “permanent” according to the Stripe criteria.
Net production driven by the upwelling pumps will be measured by integrating the particulate organic carbon measured by the backscattering sensors on a pair of robotic profiling floats within
the pump patch and outside of the patch. The robotic floats are similar to the floats used in the ARGO program and equipped with the sensor set as used in the BIO-ARGO program.
These sophisticated instruments will allow for detailed monitoring of the water column’s physical and major biogeochemical parameters within the pump footprint and the outside baseline water column. The pumps
will be programmed for daily cycling, and profiling mission parameters can be modified to keep the floats moving with the pumps.
By programming the floats to dive and resurface once per day rather than once per five or ten days, much higher resolution data is obtained, which captures many more productivity events triggered by the nutrients delivered to the sunlit upper ocean by our upwelling pumps.
A commercially available strap-on powerpack from SeaTrek operating on the ocean thermal energy principle provides near-infinite power for the BGC ARGO floats. This enables daily operating cycles essentially forever.
Risks & Challenges
Transparency on the hurdles we face ahead.
Risks our project currently faces.
- Societal rejection of ocean CDR due to outdated or incorrect information or political beliefs.
- Corporate customer decisions against ocean CDR are based on faulty assumptions, lack of knowledge, or failure to acknowledge the much higher risk from their excess CO2 under business-as-usual.
- Scientific reviewers’ reliance on outdated, incorrect, or obsolete papers, data, and information.
Modeled durability should exceed over 1,000 years, according to Dr. Stephanie Hensor (from NASEM webinar Q&A): “…the retention time depends on how deep the “extra” C may be penetrating and on the ventilation time scale of the region. For example, in the Pacific, ventilation time scales could be > 1000 years if C penetrates deeper than 1500m.”
Please note that the most urgent time to reverse atmospheric CO2 is the next 80 years. Nearly all the CO2 sequestered by our upwelling pumps will remain in the mid and deep ocean over this most critical period.
Furthermore, beyond this critical period, to the extent sequestered CO2 reappears in the upper ocean, assuming our pumps remain in operation in the region, some portion, perhaps most, of this CO2 will again be removed sequestered by freshly-grown phytoplankton in response to the nutrient upwelling. The typical approach of adopting a cut-off time when resurfacing CO2 will outgas to recognize the recurring outcomes from our pump’s upwelling deep nutrients, which trigger continuous blooms and CDR.
Upper and lower bounds on durability claimed above.
Deepwater carbon has been radiocarbon dated at 5,000 years. Shallow particulate organic carbon can remineralize and resurface under 100 years, but phytoplankton blooms triggered by our upwelling recycle this. The process is continuous, so there is no “lower bound” (period).
Have we measured this durability directly?
As implementation of ocean CDR via upwelling is a new field of activity, we rely on David Karl and Ricardo Letelier’s data and analysis.
Also, we look to the paper cited by Dr. Stephanie Henson – https://escholarship.org/uc/item/8jq8c83r.
The durability risks our project faces.
Some exported CO2 is remineralized and, overtime may reappear above the thermocline. Since our pumps operate 24/7/365, the upwelling of nutrients is continuous; therefore, the CO2 making its way to the surface layer is reprocessed biologically and re-sequestered.
Until recently, there was uncertainty on measuring and validating net CO2 export, but this has now been answered by daily sampling using the biogeochemical Argo robotic floats as discovered by Dr. Fei Chai, under the procedures set forth by Dr. Ian Walsh.
How we plan to quantify the actual permanence/durability of the carbon sequestered by our project.
We can now directly measure both quantity and depth profile using the BGC ARGO’s as further explained by Dr. Ian Walsh and Dr. Fei Chai.
Cost Per Ton
Under US$ 15 per ton CO2 removed by 2050.
The projected 2022 cost is $423 per ton removed. Phasing in new pumps annually could reduce the cost per ton to under $15 by 2050:
Without getting into too much detail the projected costs above include:
- Baseline Directo Costs per Pump FOB port
- Learning curve cost saving.
- Inflation Rate
- Costs before RR&R or Communications
- Repair, replace, reburbish (RR&R) sinking fund
- 5 year data comm cost per Argo (1 per 20)
- Adjusted cost per Autonomous Upwelling Pump
- Shipping/Loading, Staff, Travel & Onsite
- Total cost per pump
- Gross profit margin.
Stripe RFP 2021
Tons CO2 Sequestered per Array of Ten Pumps
Based on Table 1 in Karl-Letelier’s 2008 paper, each pump will sequester 251.5 tons CO2 per year attributable to the excess phosphate. Also, preliminary data from testing in the western NPSG suggest iron upwelled from 500m may increase diatom production with up to 20% additional net CO2 export. For now, our projections will include only the more-established value from Karl-Letelier.
The pump’s one-time CO2 footprint is 8.5 tons. Below is the projected cumulative net CO2 tons sequestered for this initial ten pump array:
With approval and funding by April 30, 2021, we can proceed on the following schedule.
- Woods Hole Group/CLS-France, exclusive instrumentation partner.
- Seabird Electronics, supplier of NAVIS biogeochemical ARGO robotic floats.
- SeaTrek – developer of power supply attached to BGC ARGO’s enabling unlimited measurement cycles.
- Reytek Corporation – produces hardware; final assembly; shipping; advises deployment.
- Ballotta Marine – produces high-speed workboats.
Our consulting science and engineering advisors include:
- Professor Fei Chai, University of Maine.
- Dr. Ian Walsh. Formerly Seabird Scientific Director of Science/Senior Oceanographer.
- Professor Ulf Riebesell – German Marine Research Institute-Kiel (GEOMAR).
- Professor Andreas Oschlies – German Marine Research Institute-Kiel (GEOMAR).
- Bob Hamilton, PE, President Woods Hole Group.
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