Italian Startup Limenet Is Fighting Ocean Acidification While Sequestering CO2

Italian Startup Limenet Is Fighting Ocean Acidification While Sequestering CO2 - Carbon Herald
Credit: Limenet

The increased levels of CO2 in the atmosphere emitted by humans are causing catastrophic consequences not only to the climate but also to the largest ecosystem on Earth upon which all life is dependent – the ocean.

About a quarter of our current carbon dioxide (CO2) emissions in the atmosphere are absorbed by the oceans which causes a decrease in pH levels, a process known as ocean acidification. In pre-industrial times, ocean surface acidity was pH 8.2, today it has lowered to 8.1 thanks to the increase in atmospheric CO2 concentrations.

Each decrease of 0.1 pH unit is a ten-fold increase in acidity, which according to scientists means that with the current level of ocean pH, it is around 30% more acidic compared to preindustrial times.

Credit: GOES Foundation report

Higher acidity of the ocean decreases the availability of carbonate ions. They are the main elements used by ocean organisms to build and maintain their shells and skeletons. The main marine life structures are made from calcium carbonate. That is why ocean acidification is also known as the osteoporosis of the sea.

As the ocean acidification gets higher, the ocean pH gets lower. Scientific research is showing that if the ocean pH drops to 7.8 shells and bones of marine creatures simply dissolve. It is estimated that the ocean pH will drop to 7.95 by 2045 – levels that translate into the loss of 80% to 90% of all marine life biodiversity. 

That is a tipping point or a planetary boundary that if exceeded would mean a mass extinction and a large threat to the survival of human kind. Research is showing that no ecosystem can survive a 90% loss of species and the result is a trophic cascade collapse. The loss of all corals, whales, seals, birds, and fish would also mean that the survival of 2 billion people who rely on them for food and livelihood would be threatened – an outcome worse than climate change.

The figure shows Aragonite saturation state levels estimates. Aragonite saturation state is used to track ocean acidification because it is a measure of carbonate ion concentration. The figure shows a consistent falling of aragonite saturation state below 3 expected by the end of the century. When it falls below 3, organisms become stressed, and when saturation state is less than 1, shells and other aragonite structures begin to dissolve. The predicted pH decrease of approximately 0.3 units during the 21st century would be a greater change than possibly at any time in the last 300 million years. Source: Katherine Spencer Joyce, adapted from Richard A. Feely, Scott C. Doney, and Sarah R. Cooley, Woods Hole Oceanographic Institution. GAO 14-736

One startup – Limenet offers a solution to fight ocean acidification which simultaneously mitigates the climate crisis. Limenet is an Italy-based climate tech company that has patented, tested and industrialized an innovative technology for storing CO2 in equilibrated calcium bicarbonates and then adding it to seawater to enrich its alkalinity.

We sat down and had a conversation with Stefano Cappello, founder and CEO of Limenet, who explained in more detail how the company’s technology works and how critically important it is to reverse ocean acidification right now in order for the ocean ecosystem to survive. 

“We started Limenet as a company that wants to mitigate ocean acidification with CO2. Our main goal is to fight ocean acidification,” said Mr Cappello.

Limenet’s technology involves the replication of the geological cycle of carbon on Earth that stores CO2 in the deep ocean with carbonates ions. This is how CO2 is naturally absorbed during millennia by seawater. However, Limenet increases the speed of this natural process to hour scale.

It works as the company processes waste biomass, which naturally contains CO2, in an oxy-combustion gasifier in order to produce biogenic CO2 and heat. The heat is used to make the calcination of limestone. The calcination is the process of heating the limestone which separates it into quicklime and a gas stream of carbon dioxide.

Limenet process. Credit: Limenet

The technology uses two CO2 streams – one from oxy-combustion of biomass and the other from the calcination of limestone. All the carbon dioxide is used to make an equilibrated solution of calcium bicarbonate. The calcium bicarbonate is then added to the ocean to boost alkalinity. It has the same pH of seawater (8.1-8.2) but higher alkalinity and is in equilibrium with the atmosphere.

Being already in equilibrium with the atmosphere, it is able to decrease the process uncertainties for the MRV protocol. The equilibrated calcium bicarbonate does not release the CO2 stored in it when it is added to the ocean and indirectly increases ocean pH. Indeed, enhancing the level of alkalinity increases the buffering effect of water and so its capability to avoid pH variation with higher levels of CO2 in the atmosphere.

Relevant: “Ocean Alkalinity Enhancement Is By Far The Largest Scale Potential Carbon Removal We Have Available To Us” – Mike Kelland, CEO Planetary Technologies

Instead of using biogenic CO2, Limenet can also use a direct stream of CO2 coming from the hard to abate industry or direct air capture facilities. The same CO2 will then be combined with Limestone and seawater to produce the equilibrated calcium bicarbonate ionic solution. In this second approach, the first step which is the oxy-combustion gasification of biomass is avoided.

Instead of using heat, Limenet uses renewable energy electricity for an electric calcination of limestone. The company has proven its concept at a pilot plant it has developed in La Spezia, Italy, at a Technology Readiness Level (TRL 6). 

Limenet pilot plant. Credit: Limenet

The pilot plant has a maximum production of 10 kg/h of decarbonized calcium hydroxide and a maximum storage capacity for CO2 of 1 kg/h in the form of equilibrated calcium bicarbonates ionic solution. The total emissions amount stored was approximately 150 kg.

Limenet is currently building a first-of-a-kind modular industrial plant in South Italy that will be able to capture and store 4000 tons of CO2 per year. The company will soon release further updates about the plant.

To a question from Carbon Herald regarding the recent criticism from the science community questioning the safety of ocean acidification methods, Mr Cappello said that he understands many scientists have fear because we don’t really know the complexity of the ocean in all detail, however, he also pointed out: “I have more fear not to do anything than trying to do something… What is happening to the ocean is crazy bad.”

Relevant: New Research Will Assess Efficiency Of Ocean Alkalinity In Removing CO2 From The Air

As ocean acidification is decreasing the quantities of calcium carbonates due to more CO2 being dissolved into the seawater, the world is now facing a situation where these critically low levels of carbonates can cause a mass extinction of marine species.

According to Limenet’s studies, we need to introduce gigatons of carbonates in the oceans in order to preserve the ecosystem and marine life. It is so urgent now to restore balance in ocean chemistry that the benefits from adding calcium bicarbonate and calcium carbonate can far exceed any hypothetical risks.

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