Planetary Technologies (Planetary) focuses on ocean-based carbon removal technology which works by producing magnesium hydroxide (Mg(OH)₂) from MgSiO₃ rocks through electrolysis technology and adding Mg(OH)₂ to seawater to speeds up the ocean’s natural carbon sequestration process and lowers ocean acidity. This process converts the dissolved carbon dioxide (CO₂) into a mineral salt, which will remain in that state for 100,000 years. Planetary aims to remove 1 billion tons of CO₂ from the atmosphere by 2045.
Challenges: Ocean-based carbon removal
Since the early 1900s, carbon dioxide (CO₂) levels in the atmosphere have increased by 50% due to human activities. When fossil fuels (such as coal, oil, and natural gas) are burned for energy production, transportation, and industrial processes, CO₂ is released into the atmosphere. This excess CO₂ acts as a greenhouse gas, trapping heat and causing the air and ocean temperatures to rise. CO₂ emissions play a crucial role in driving climate change.
This warming effect has caused the global average temperature to rise by about 1.1 ºC since the pre-industrial period. This has led to rising in the frequency and intensity of extreme weather events, melting of polar ice caps and glaciers and rising sea levels, shifts in species ranges and increased risk of species extinction, agriculture and food security, and ocean acidification.
To mitigate these impacts, the Paris Agreement aims to limit global warming to well below 2 ºC above pre-industrial levels. The Intergovernmental Panel on Climate Change (IPCC) estimates that a “carbon budget” of about 500 GtCO₂, which corresponds to about ten years at current emission rates, provides a 66% chance of limiting global warming to 1.5 ºC.
Ocean carbon sequestration
The oceans cover more than 70% of the earth’s surface. They store a lot of CO₂. They are the largest carbon sink on the planet, absorbing about 40% of the CO₂ emitted by human activities. They are an important buffer in climate change.
At its current average pH of 8.1, seawater contains 150 times more CO₂ than an equal volume of the air. The seawater locks the atmospheric CO₂ in the form of ions (HCO₃⁻ and CO₃²⁻) and solid precipitates (CaCO₃ and MgCO₃) according to the following reversible chemical reactions:
CO₂ + H₂O ⇆ H₂CO₃
H₂CO₃ ⇆ H⁺ + HCO₃⁻
HCO₃⁻ ⇆ H⁺ + CO₃²⁻
CO₃²⁻ + Ca²⁺ ⇆ CaCO₃↓
CO₃²⁻ + Mg²⁺ ⇆ MgCO₃↓
As CO₂ emissions increase, the ocean absorbs more CO₂, forming more carbonic acid and lowering the ocean’s pH, making it more acidic. As the oceans absorb more CO₂ than they can handle, it could lead to several potential consequences, such as ocean acidification. Ocean acidification can have negative effects on marine life, particularly organisms with calcium carbonate shells or skeletons, such as corals, mollusks, and some plankton species.
Ocean Alkalinity Enhancement
Ocean Alkalinity Enhancement (OAE) is a technical carbon removal approach that involves adding alkaline substances to seawater to enhance the ocean’s natural carbon sink. It is one of the important Negative emissions technologies (NETs). NETs are important because they can help companies, sectors, or countries remove more CO₂ from the atmosphere than they emit. According to climate models, a significant deployment of NETs will be needed to prevent catastrophic ocean acidification and global warming beyond 1.5 ºC.
By increasing the alkalinity of seawater, the above chemical reactions shift towards right, resulting in more dissolved CO₂ and converting more CO₂ to bicarbonates (HCO₃⁻), and carbonates (CO₃²⁻), according to the following chemical reactions:
CO₂ + OH⁻ → HCO₃⁻
HCO₃⁻ + OH⁻ → CO₃²⁻ + H₂O
Bicarbonates and carbonates are stable forms of carbon in the ocean. Therefore, the Ocean Alkalinity Enhancement process accelerates the ocean’s natural ability to sequester CO₂ from the atmosphere, helping to mitigate climate change and ocean acidification.
While OAE has the potential to remove significant amounts of CO₂ from the atmosphere, there are concerns about its environmental impacts, such as the effects on marine organisms and ecosystems. Further research is needed to fully understand the potential risks and benefits of OAE, as well as the feasibility, cost, and scalability of this approach.
Ocean Alkalinity Enhancement companies
Several companies are developing the Ocean Alkalinity Enhancement technology, such as Ebb Carbon and Equatic.
Ebb Carbon company has developed an Ocean Alkalinity Enhancement system that uses renewable energy and an electrodialysis stack to produce NaOH base solution. The base solution is added to the seawater in a controlled manner and safely increases the local pH to create a natural chemical reaction that removes CO₂ from the air.
Equatic company has developed a transformative electrolytic method for CO₂ removal that leverages the high concentration of CO₂ in seawater and the enormous abundance of Ca²⁺ and Mg²⁺ cations. The in-situ alkalization of seawater in electrolytic flow reactors forces CO₂ mineralization via reactions between dissolved CO₂ and Ca²⁺ and Mg²⁺ to permanently lock CO₂ as stable carbonate solids and/or as aqueous bicarbonates. The process also produces green hydrogen (H₂) that can be used to fuel the process during intermittency or sold to generate revenue.
How does Planetary technology work?
Planetary has developed an approach of Ocean Alkalinity Enhancement by electrochemically producing magnesium hydroxide (Mg(OH)₂) substance via an electrolyzer and safely adding Mg(OH)₂ to seawater by using a floating platform.
Planetary’s electrolyzer system electrolyzes sodium sulfate (Na₂SO₄) electrolyte to produce sulfuric acid (H₂SO₄) and sodium hydroxide (NaOH) base in order to convert MgSO₃ minerals into Mg(OH)₂. Due to its low toxicity to aquatic organisms and humans, Mg(OH)₂ is commonly used in wastewater treatment. Important aspect of Mg(OH)₂ is its sluggish dissolution, which limits its environmental impact. This prevents rapid pH rises at the outfall location, after which rapid dilution in the seawater maintains a pH well within safe limits.
Planetary has also developed a floating platform for safely dispersing Mg(OH)₂ in the ocean for carbon dioxide sequestering. The platform has a vessel for holding solid Mg(OH)₂ pellets and exposes them to a flow of seawater to create a Mg(OH)₂ solution with a safe pH level. The solution is released into the seawater, producing HCO₃⁻ or MgCO₃ solid, thus sequestering CO₂ present in seawater through chemical reactions:
Mg²⁺ + 2OH⁻ + 2CO₂ → Mg²⁺ + 2HCO₃⁻
Mg²⁺ + OH⁻ + HCO₃⁻ → MgCO₃↓ + H₂O
How does Planetary produce magnesium hydroxide?
The diagram below depicts Planetary’s electrolyzer system for producing Mg(OH)₂ from MgSiO₃ minerals and generating green hydrogen gas ( H₂) as a by-product, which could be used as a zero-carbon fuel.
The system mainly comprises an electrolyzer, a leaching tank, and a Mg(OH)₂ reactor.
The electrolyzer electrolyzes Na₂SO₄ electrolyte and produces H₂SO₄ and NaOH solutions. The acid solution is used to leach MgSO₃ minerals in a leaching tank, while the base solution is used to precipitate Mg(OH)₂ from the leaching solution in a separate Mg(OH)₂ reactor.
The electrolyzer uses two anion exchange membranes (AEMs) to create a three-chambered electrolytic container: an anode chamber, a cathode chamber, and a central chamber. The central chamber is supplied with Na₂SO₄ electrolyte recycled from the Mg(OH)₂ reactor, while the anode and cathode chambers are supplied with water to compensate for of water lost during electrolysis reactions.
When sufficient applied voltage on the anode and cathode, OH⁻ and H₂ are generated at the cathode according to the chemical reactions:
2H₂O + 2e⁻ → 2OH⁻ + H₂↑
Hydroxide ions transport to the central chamber, where they combine with sodium ions to form NaOH base solution. Hydrogen gas is removed and used as clean fuel.
On the anode, H₂O is electrically oxidized into oxygen gas (O₂) and protons (H⁺) via the chemical reaction:
2H₂O → 4e⁻ + 4H⁺ + O₂↑
The oxygen gas is removed. The protons combine with SO₄²⁻ ions that migrate from the central chamber via the anion exchange membrane to form H₂SO₄. The acid is introduced to the leaching tank to leach MgSO₃ minerals.
The overall chemical reaction occurs in the electrolyzer can be described below:
Na₂SO₄ + 3H₂O → H₂↑ +½ O₂↑ + H₂SO₄ +2NaOH
- Leaching tank
H₂SO₄ formed in the anode chamber is supplied to a separate leaching tank. The acid dissolved the MgSiO₃ mineral rocks in the tank according to the chemical reaction:
H₂SO₄ + MgSiO₃ rock (containing other metal silicates and oxides) → MgSO₄ + H₂O + SiO₂ + other metal compounds
The leaching solution is processed by a cleanup unit. Silica (SiO₂) and other metal compounds are removed while the remaining MgSO₄ solution is delivered to the Mg(OH)₂ reactor.
- Mg(OH)₂ reactor
In the Mg(OH)₂ reactor, MgSO₄ solution is mixed with NaOH solution from the central camber of the electrolyzer. Mg(OH)₂ is precipitated from the solution. The process can be described via the chemical reaction:
Mg²⁺ + SO₄²⁻ + 2Na⁺ + 2OH⁻ → 2Na⁺ + SO₄²⁻ + Mg(OH)₂↓
The Mg(OH)₂ precipitate is separated from the Na₂SO₄ solution via flocculation followed by settling-thickening filtration, centrifugation or other solid/liquid separation methods. The Na₂SO₄ solution is then recycled back into the central chamber of the electrolyzer to provide fresh electrolyte.
Planetary ocean-based carbon removal with floating platform
Adding Mg(OH)₂ into seawater causes an increase in initial pH levels around the outfall location. When the initial pH level at the outfall location exceeds 9, undesirable precipitation of CaCO₃ and generation of CO₂ occur according to the following chemical reaction:
Ca²⁺ + 2HCO₃⁺ → CaCO₃↓ + CO₂↑ + H₂O
In order to maximize CO₂ removal and storage, it is evident that the concentration of dissolved Mg(OH)₂ released to the ocean must be controlled in order to avoid the undesirable precipitation of CaCO₃. Planetary has performed MRV tests and concluded that the release rate of Mg(OH)₂ must be controlled so that seawater alkalinity concentrations do not exceed about 4 mmol/L.
Planetary has therefore developed a floating platform system, as shown in the diagram below, for the addition of Mg(OH)₂ solution to seawater in order to maintain seawater pH within safe environmental limits while maximizing CO₂-removal and sequestration and avoiding undesirable changes to seawater chemistry, including avoiding precipitation of CaCO₃.
The platform mainly comprises a Mg(OH)₂ stock container, sensors, pumps, and computer (not shown).
- Mg(OH)₂ stock container
The container contains solid Mg(OH)₂ pellets or particles. A dispenser in the container is triggered by a sensor associated with the dispenser and releases the required amount of Mg(OH)₂ in the hull of the floating platform upon receiving the dispensing signal. The required quantity is calculated by the computer inside the floating platform.
The floating platform has a pump for pumping seawater from the ocean into the hull to dissolve the Mg(OH)₂ pellets and dilute the Mg(OH)₂ solution. There is another pump for pumping the Mg(OH)₂ solution from the hull to the ocean. Both pumps are controlled by the computer.
The floating platform has a communication sensor controlled by the computer for sending a communication signal to outside entities for loading Mg(OH)₂ pellets in the container and relocating the floating platform to different locations in the ocean.
The floating platform has sensors for measuring pH of the solution in the hull and characteristics of the seawater surrounding the floating platform, such as pH and inorganic carbon.
Additionally, the floating platform has sensors for measuring lower and upper water levels inside the hull to ensure the water level is within a predetermined range.
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Carbon offset credit market
The market value of carbon offset credits varies widely. In current carbon markets, the price of one carbon credit can range from a few cents per metric ton of CO₂ emissions to $15/mtCO₂e (metric tons of CO₂ equivalent) or even $20/mtCO₂e. However, the voluntary carbon offset market, which was worth about $2 billion in 2021, is projected to grow to $10-40 billion by 2030, transacting 0.5-1.5 billion tons of CO₂ equivalent, as opposed to the current 500 million tons. The total value of carbon credits produced and sold to help companies and individuals meet their de-carbonization goals could approach $1 trillion as soon as 2037.
Planetary science projects
Planetary has a small project in Cornwall that aims to determine if Planetary’s carbon removal technology can scale up safely and effectively. The project involves small and well-monitored trials in Hayle, UK, to remove carbon from the atmosphere while restoring marine ecosystems. Planetary has held two public consultations in the local area to hear from residents and those working hard to protect Cornwall and its environment. The company intends to update plans to account for local community feedback. All results from the test will be released publicly, in keeping with their Code of Conduct and integrity to their research and people.
Planetary has raised a total of $8.6M in funding over 6 rounds, including
Their latest funding was raised on Apr 22, 2022 from a Grant round.
Planetary is funded by 9 investors, including
- UK government
- Government of Canada
- Apollo Projects
- Ocean Startup Project
- Canadian Technology Accelerator
- Capital Angel Network
- Ramen Ventures
Mike Kelland is CEO.