Abstract
Limenet is an Italian deep tech startup that has patented an innovative technology to remove and permanently store – for a period of more than 10 thousand years – carbon dioxide (CO2) by storing it in the sea in the form of calcium bicarbonates. Limenet’s technology on the one hand transforms carbon dioxide into calcium bicarbonates, counteracting climate change; on the other hand, by dissolving carbonate compounds in seawater, it increases its alkalinity, i.e. the ability to resist changes in acidity levels, with benefits for the marine ecosystem. Founded by Stefano Cappello (CEO & Founder), engineer and researcher, together with Giovanni Cappello (CTO & Co-founder), – one of the greatest experts in Italy in gasification – and Enrico Noseda – already co-founder of successful startups such as HLPY and Chief Innovation Advisor of Cariplo Factory –, it is today one of the few startups in the world to use the sea as a basin for CO2 storage and aims to become an international leader in the capture and storage of CO2 through calcium bicarbonates.
The plant inaugurated in Augusta in September 2024 is the largest in the world in terms of production capacity for CO2 storage – 100kg/h – at sea in the form of calcium bicarbonates (Ocean Vision database).
Limenet: Permanent carbon storage in seawater
Limenet’s process captures excess CO2 using a chemical method, used by nature for millions of years and at the same time regenerates the world’s seas from the acidification that threatens life underwater and on the surface.
Its technological proposal aims to increase the ocean’s capacity to absorb carbon dioxide from the atmosphere through the alkalinization of the sea. Here is the promise of the startup: «The largest CO2 storage facility in Iceland, valued at around 4 billion dollars, captures 30 thousand tons of CO2 per year: with Limenet we can do it in 20 days», explains Jacopo Visetti, co-founder of Aither and main investor of Limenet.
Storing CO2 in the sea: Limenet technology
What Limenet technology needs is very simple: sea water, renewable energy and calcium carbonate. The latter «is one of the most widespread materials, there is more than we need», explains Stefano Caserini, professor at the University of Parma and scientific advisor of Limenet. «Calcium carbonate represents as much as 7% of the entire Earth’s crust».
This technological innovation, based on chemical processes, is able to transform carbon dioxide, collected from the atmosphere or other sources, into an aqueous solution of calcium bicarbonates. In this way, a long-lasting and stable CO2 storage solution (for over 10 thousand years) is created within seas and oceans. In fact, it involves using the same methodology as the geological carbon cycle, a natural process through which carbon in the atmosphere is exchanged with the soil, seas and oceans, and fresh water such as lakes and rivers. In fact, the largest deposits of CO2 on Earth are seas and oceans, which assimilate this gas through saltwater and neutralize its acidity through the action of carbonate rocks. Today, however, the extreme diffusion of carbon dioxide of anthropogenic origin on the planet has overloaded seas and oceans: it is estimated that 30% of the total has ended up under water.
Through the use of calcium bicarbonate, Limenet promises to capture CO2 in the atmosphere, store it safely and at the same time counteract the acidification of the seas through the alkalinization triggered by the bicarbonate produced.
Here is the process of Limenet’s technology, entirely powered by renewable energy: to extract CO2 from the atmosphere (or to collect co0 by other factories), then crush the calcium carbonate, transform it into quicklime and then rehydrate it and make it slaked lime. Finally, store the CO2: just over half of the slaked lime obtained is used to remove the carbon dioxide produced, while the other half is available for capturing the CO2. The entire process allows the production of negative CO2 emissions.
In this pioneering phase, the Limenet reactor installed in the commercial port of Augusta, Sicily also activates circular economy logics since the calcium carbonate used by the startup is extracted in the quarries of “Leone La Ferla” in Melillli in the province of Syracuse, the only lime producer in Sicily and one of the investor in Limenet’s technology. A similar process also occurs for carbon dioxide: thanks to an agreement with the multinational Nippon Gases, the CO2 stored at sea is that produced by the IREN biogas plant near Reggio Emilia, which is obtained from the disposal of organic waste and urban biomass collected in the province of Reggio Emilia.
The first plant in the world in Augusta
Today in Augusta the first Limenet plant was born: the first in the world to use this method of storing CO2 at sea. TRL7 is now being developed: the goal is to reach the TRL9 stage, that is, a plant capable of creating industrial applications. For example, offering the possibility of compensation on the CO2 credit market through the production of calcium bicarbonates to be poured into the sea. The company has already sold the first CO2 credits equivalent to 1,000 tons (tons) of negative emissions.
Stefano Cappello, CEO and founder of Limenet, explains: «With the Augusta plant, the continuous operation of the technology will begin, with a production capacity of 100kg/h of CO2 stored in the form of calcium bicarbonates. Our goal for this plant and the next ones is to achieve the expected economies of scale, with a reduction in removal and storage costs».
A scalable solution for gigatons of CO2
Limenet has currently obtained 5 million euros in funding and is aiming to raise another 5. One of its strengths is presenting a modular solution, which promises to be scaled to any size: according to company forecasts, at mega-ton scale by 2035, at multi-mega-ton scale by 2045 and at giga-ton scale by 2055.
As Cappello explains: «Through our techno-economic analyses, using the scaling factors called ‘learning rate’, it is possible to have an industrial plant that can generate 100 thousand tons per year of negative emissions with a cost per ton of around 100 dollars: a goal considered realistic, especially if we follow the cost reduction trends seen in other green technologies».
At the moment – in the world and in absolute terms – about 10 thousand tons of CO2 have been removed but it will be necessary to reach 10 billion tons of CO2 by 2050 to reach the targets set by the Paris Agreement.
