Limenet’s vision is that, for several factors that we will go into this section, calcium bicarbonates are one of the most effective solutions to store CO₂, even for a very long time perspective.
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Bicarbonates
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Geological storage
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Trees
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|---|---|---|---|
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CO₂ sequestration rate
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Minutes
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Years
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Decades
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|
Stability of the CO₂ stored over time
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10⁴-10⁵ years
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10⁵ years
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Vulnerable to climate change
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Environmental co-benefits
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Counteracting ocean acidification
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N/A
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In some cases improvement of biodiversity
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|
Scalability
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High*
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High
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Medium
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Planning
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Financial modularity
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Geological feasibility studies
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Yes
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* High scalability thanks to the presence of the sea and calcium carbonate
Differences between Ocean Alkalinity Enhancement and pH Ocean Alkalinity Enhancement
The pH equilibrated Ocean Alkalinity Enhancement (OAE) approach applied by Limenet is an alternative to the OAE method of adding alkaline minerals directly in the sea. The main difference is that the dissolution occurs in a reactor, which is a controlled volume that ensures the complete dissolution of lime and the release of a transparent marine solution rich in bicarbonates, instead of causing a local increase in turbidity due to mineral dispersion as happens with OAE. Since the marine solution released by Limenet plants has the same pH as the sea, the local abrupt pH spike with OAE is avoided. At the same time Limenet solution indirectly combats ocean acidification by increasing the sea’s buffering effect.
Historical use cases
An example that can be cited regarding the use of carbonate substances to combat the acidity of water is the experiment conducted in Lake Orta. Here, between 1989 and 1991, acidification was reduced and remedied thanks to calcium carbonate’s introduction, thus producing calcium bicarbonate (Calderoni et al).
The pH of the lake was “restored” in two years of adding calcium carbonate that melting in water turned into calcium bicarbonate.
The boat Sant’Angelo during the spreading operations in Lake Orta (1990)
Trend of the monthly (1990-2000) and quarterly (since 2001) values of pH (a), alkalinity (b), dissolved oxygen (c) and nitrate (d) in the epilimnion and hypolimnion of Lake Orta. ¹
This is evident from the graph beside, which shows that the alkalinity of the lake has increased over time, demonstrating the conversion of carbonates into calcium bicarbonates.
Based on the same principle, directly introducing calcium bicarbonates into marine waters helps counteract ocean acidification.
The similarities and differences between the Liming made in Lake Orta and Limenet are as follows:
Similarities
Differences
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pH at the point of insertion of bicarbonates
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Bicarbonates formation
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Control of formation of bicarbonates
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Solution turbidity
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Acidification contrast
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Insertion
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CO₂ absorption from the atmosphere
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|---|---|---|---|---|---|---|---|
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Liming
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9-10*
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In the sea
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No
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Medium for some minutes
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Direct
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Injection at a few meters depth
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Yes
|
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Limenet
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8.2 in a controlled and monitored way
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Inside Limenet reactor before injection
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Yes
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Very low, transparent
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Indirect (buffer effect)
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Under the surface layer
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No, just storage
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* Depending on the modality of implementation
Sources
¹ Jlimnol.it. (2016) https://www.jlimnol.it/jlimnol/article/view/jlimnol.2016.1320/846f