Acidification Mitigation Details and lower cost mitigation in the $1 to 4 per ton CO2 ranges

Ocean Acidification: Cause, Impact and mitigation from IIT Kanpur

Limestone mitigation

Presentation by Rau describes the limestone mitigation method

Journal of Geophysical Research - Mitigating the atmospheric CO2 increase and ocean acidification by adding limestone powder to upwelling regions

The feasibility of enhancing the absorption of CO2 from the atmosphere by adding calcium carbonate (CaCO3) powder to the ocean and of partially reversing the acidification of the ocean and the decrease in calcite supersaturation resulting from the absorption of anthropogenic CO2 is investigated. CaCO3 could be added to the surface layer in regions where the depth of the boundary between supersaturated and unsaturated water is relatively shallow (250–500 m) and where the upwelling velocity is large (30–300 m a 1 ). The CaCO3 would dissolve within a few 100 m depth below the saturation horizon, and the dissolution products would enter the mixed layer within a few years to decades, facilitating further absorption of CO2 from the atmosphere. This absorption of CO2 would largely offset the increase in mixed layer pH and carbonate supersaturation resulting from the upwelling of dissolved limestone powder. However, if done on a large scale, the reduction in atmospheric CO2 due to absorption of CO2 by the ocean would reduce the amount of CO2 that needs to be absorbed by the mixed layer, thereby allowing a larger net increase in pH and in supersaturation in the regions receiving CaCO3. At the same time, the reduction in atmospheric pCO2 would cause outgassing of CO2 from ocean regions not subject to addition of CaCO3, thereby increasing the pH and supersaturation in these regions as well. Geographically optimal application of 4 billion t of CaCO3 a 1 (0.48 Gt C a 1 ) could induce absorption of atmospheric CO2 at a rate of 600 Mt CO2 a 1 after 50 years, 900 Mt CO2 a 1 after 100 years, and 1050 Mt CO2 a 1 after 200 years.

Opportunities for Low-Cost CO2 Mitigation in Electricity, Oil, and Cement Production by Rau

Several low-cost opportunities exist for scrubbing CO2 from waste gas streams, utilizing spontaneous chemical reactions in the presence of water and inexpensive or waste alkaline compounds. These reactions convert CO2 to bicarbonate or carbonate in dissolved or solid form, thus providing CO2 capture and low-risk CO2 storage underground, in the ocean, or in some cases on land. Useful by-products and co-benefits can also be generated by these processes. In certain settings this approach will be significantly less energy intensive, less costly, and less risky than "conventional" molecular CO2 capture and geologic storage.

It has been previously shown that industrial-scale accelerated weathering of limestone, AWL, can effectively convert a significant fraction of US CO2 emissions to long-term storage as bicarbonate in the ocean. Being analogous to the successful, wide-spread use of wet limestone to desulfurize flue gas, AWL reactors could be retrofitted to existing power plants at a cost possibly as low as $3-$4 per tonne CO2 mitigated. Such low costs would especially pertain to coastal power plants where an average of 30,000 tonnes of seawater per GWhe are already pumped through for cooling, and where the majority of coastline (at least in the US) is within 400 km of limestone sources.

Capture and Storage Using Water Co-Produced With Oil

On average 10 barrels of water are brought to the surface with each barrel of oil produced, and the majority of this water is simply pumped back into the reservoir. Our preliminary analysis suggests that most of this water is significantly undersaturated in CO2 relative to industrial waste gas streams that are typically 10% to 20% CO2. Furthermore, such waters can contain significant carbonate ion concentrations, meaning they have an enhanced capacity to react with excess CO2 to form dissolved bicarbonates.

While the US capacity of this CO2 mitigation approach is modest (perhaps 2 million tons/yr) and is best suited to treat CO2 waste streams in the immediate vicinity of the water production, the cost of such CO2 mitigation could be extremely low, perhaps less than $1/tonne CO2.

Co-benefits of CO2 addition to produced water would be the reduction (via lowered pH) of internal pipeline scale formation, a common and expensive problem in the industry. Also, CO2 addition could enhance the oil-water separation process, may reduce downstream microbial fouling, and might enhance oil recovery. Further work is needed to better evaluate the cost/benefit and potential market of this CO2 mitigation approach.

Cement Production can be altered to absorb CO2 instead of releasing CO2.

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Ocean Acidification $2 million XPrize

The Wendy Schmidt Ocean Health XPRIZE is a $2 million global competition that challenges teams of engineers, scientists and innovators from all over the world to create pH sensor technology that will affordably, accurately and efficiently measure ocean chemistry from its shallowest waters… to its deepest depths.

There are two prize purses available (teams may compete for, and win, both purses):

A. $1,000,000 Accuracy award – Performance focused ($750,000 First Place, $250,000 Second Place): To the teams that navigate the entire competition to produce the most accurate, stable and precise pH sensors under a variety of tests.

B. $1,000,000 Affordability award – Cost and Use focused ($750,000 First Place, $250,000 Second Place): To the teams that produce the least expensive, easy-to-use, accurate, stable, and precise pH sensors under a variety of tests.



The Need for the Prize - The Problem

Our ocean is currently in the midst of a silent crisis. Rising levels of atmospheric carbon are resulting in higher levels of acidity. The potential biological, ecological, biogeochemical and societal implications are staggering. The absorption of human CO2 emissions is already having a profound impact on ocean chemistry, impacting the health of shellfish, fisheries, coral reefs, other ecosystems and our very survival.

The Need for the Prize - The Market Failure

While ocean acidification is well documented in a few temperate ocean waters, little is known in high latitudes, coastal areas and the deep sea, and most current pH sensor technologies are too costly, imprecise, or unstable to allow for sufficient knowledge on the state of ocean acidification.

The Need for the Prize - The Solution

Breakthrough sensors are urgently needed for scientists, managers and industry to turn the tide on ocean acidification and begin healing our ocean. A competition to incentivize the creation of these sensors for the study and monitoring of ocean acidification’s impact on marine ecosystems and ocean health will drive industry forward by providing the data needed to take action and produce results.

The Need for the Prize - Impact

Making a broad impact—one that reaches far beyond new sensing technologies—is critical to the success of the prize. It begins with a breakthrough pH sensor that will catalyze our ability to measure—and thus respond to—ocean acidification.

But the breakthroughs go far beyond this impact:

* Provide tools for the study and monitoring of ocean acidification’s impacts on marine creatures and ecosystems, and thus ocean health
* Catalyze ocean acidification research
* Catalyze the development of the ocean services industry – data, information, forecasting and more for global industry
* Inspire innovations in ocean sensing technology broadly for deployment in many platforms and to effectively monitor the health of the ocean
* Create both tools and support for policymakers and public officials
* Inspire the public to engage in solving ocean acidification

To learn more about the science behind ocean acidification, visit
NOAA’s Pacific Marine Environmental Laboratory

For more information on the impacts of ocean acidification on humans and marine life, visit
the NRDC’s website

NRDC has produced a film diving into the causes and consequences of ocean acidification:
http://www.nrdc.org/oceans/acidification/aboutthefilm.asp

For more on what you can do to help, visit the Deeper Dive at Ocean Conservancy:
http://www.oceanconservancy.org/our-work/ocean-acidification/deeper-dive.html

Counter Acting Ocean Acidication

Ten Ways States Can Combat Ocean Acidification (and Why they should) by Ryan P. Kelly* and Margaret R. Caldwell [48 page paper by Stanford researchers]

The ocean is becoming more acidic worldwide as a result of increasing atmospheric concentrations of carbon dioxide (“CO2”) and other pollutants. This fundamental change is likely to have substantial ecological and economic consequences globally. In this Article, we provide a toolbox for understanding and addressing the drivers of ocean acidification. We begin with an overview of the relevant science, highlighting known causes of chemical change in the coastal ocean. Because of the difficulties associated with controlling diffuse atmospheric pollutants such as CO2, we then focus on controlling smaller-scale agents of acidification, discussing ten legal and policy tools that state government agencies can use to mitigate the problem. This bottom-up approach does not solve the global CO2 problem, but instead offers a more immediate means of addressing the challenges of a rapidly changing ocean. States have ample legal authority to address many of the causes of ocean acidification; what remains is to implement that authority to safeguard our iconic coastal resources.

Mitigating Acidification

Ocean Acidification: Cause, Effect, and Potential Mitigation Approaches by Joanna M. Norton

The accumulation of carbon dioxide in Earth’s atmosphere is mirrored by an increase in dissolved carbonic acid in the oceans. Carbon dioxide dissolves easily into liquid, so the surface layers of the ocean are always in equilibrium with atmospheric pressures of the gas and provide a massive sink. Some of the dissolved carbon dioxide remains as carbonic acid, some breaks down further to form carbonate ion, but most is present in the form of bicarbonate (HCO3-); these are the components of the ocean’s buffering system to guard against pH changes. However, the buffer can be overwhelmed by continued inputs of carbon dioxide and lose its buffering capacity.

1) Sequestering carbon on the ocean floor by fertilizing certain ocean regions with iron, which can be a limiting nutrient in these areas

2) Addition of powdered limestone to ocean water to react with carbon dioxide and form bicarbonate has also been proposed (Rau and Caldiera 1999; Harvey 2007). This would neutralize the acidity of the added carbon dioxide, as well as push the oceanic carbon equation towards carbonic acid and allow for more calcium carbonate to stay undissolved in the shells of marine life. The ocean has a large, untapped ability to hold dissolved bicarbonate, if enough calcium carbonate (limestone) is made available for the reaction (Rau et al 2006). This process would essentially increase the buffering capacity of the ocean, by adding carbonate ion to offset the carbon dioxide absorbed by the ocean. Rau et al (2006) calculate that the ocean could hold enough bicarbonate that all the carbon in existing fossil fuel stores could be sequestered. In fact, this is how past rises in atmospheric carbon were eventually modulated, gradually, over millennia. They suggest accelerated weathering of limestone at locations of CO2 production. Harvey (2007) investigates adding powdered limestone to areas that would carry it in upwelling current. This method could be especially cheap and effective, and no negative side effects have been found, but these issues have not been thoroughly examined.


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