Limenet is entering a rapidly changing market. Among the most likely scenarios, Limenet provides the use of CO₂ industrial source of players that need ‘reduce’ emissions or operate in partnership with players DAC (Direct Air Capture). Limenet’s product, however, is focused on the production of “decarbonized calcium hydroxide” which can be used both for the storage of CO₂ from external sources and for the capture and storage of CO₂ from flue gas or from the atmosphere.

The current business model with a completely immature market involves the management of the (capital intensive) facilities for the production of decarbonized calcium hydroxide. The same calcium hydroxide can be used in different ways to achieve negative emissions or the sole storage of CO₂. With the increase of the level of maturity of the market will open presumably other opportunities and other models will be evaluated.

Both technologies start from the same raw material: Calcium Carbonate. This, once transformed into calcium hydroxide is used to make calcium bicarbonates as a solution to remove CO₂.  However, the differences between the two methods are many: Liming involves the shedding of decarbonized calcium hydroxide in the wake of a ship. The mixing given by the turbulence of the ship facilitate the hydroxide exchange of CO₂ with the ocean surface allowing the formation of calcium bicarbonates. Limenet instead provides for the controlled introduction of a flow of CO₂ in reactors with seawater and calcium hydroxide. The alkaline solution with the CO₂ stored in the form of bicarbonates is measured and then dispersed at sea. In the following table we can see the characteristics and differences between the two methods:

	Liming	Limenet
Method	Calcium hydroxide dispersion in the wake of a vessel	Introduction of CO₂, calcium hydroxide and seawater in reactors where calcium bicarbonates are converted in a controlled way
Monitoring	N/A	Industrial monitoring with pH, Turbidity, Alkalinity and TIC sensors
Process efficiency	70%	95%
Chemical efficiency	70%	95%
Chemical stability	10’000 – 100’000 yrs	10’000 – 100’000 yrs
pH	10-12	8.15 – there is no alteration of the marine pH
Secondary precipitation	Absent if the solution is diluted quickly under omega 5	Absent
Biotic precipitation	Present because the addition of alkalinity is in the photic zone	It depends on the depth of the discharge point. If under the photic zone is absent
CO₂ exchange with the atmosphere	Still uncertain	Not necessary because the alkaline solution is already balanced with the atmosphere

Bicarbonates are defined in the literature as a solution that has the potential to counteract the acidification of the sea. However, to make bicarbonates there are different methodologies. Among the most famous are the Liming, also called OAE (ocean Alkalinity Enhancement), EWL (Enhanced Weathering of Limestone), EWO (Enhanced Weathering of Olivine). These solutions however have some Drawback like the fact of locally varying the marine pH potentially damaging biota. There are several researches about it that study the effect on the marine biota of OAE such as a research conducted by the Polytechnic and EULA (not yet published), a research conducted by the GEOMAR institute and many others. However, Limenet’s solution is different. A solution with greater alkalinity but with the same sea pH is introduced into the sea. This solution is internally called BOAE (Buffered Ocean Alkalinity Enhancement). Research that goes to study only the behavior of marine biota at different alkalinities but with the same pH are few.  Among the most relevant we can find:

• Ecosystem impacts of Ocean Alkalization in an oligotrophic marine plankton community: A mesocosm study.

Pelagic mesocosms were deployed in Taliarte (Gran Canaria), enclosing 8 m³ of oligotrophic coastal waters with their associated natural plankton community. Nine OAE addition scenarios were simulated, increasing alkalinity (TA) in steps of 300 µeq/L from ambient levels up to its doubling, using a mixture of sodium carbonate and bicarbonate. 33-day experiment. Here, only 4 out of the over 30 different stability, food quantity and quality proxies were significantly affected by enhanced TA. Out of these, two were interpreted as negative impacts: a shorter-term halving in small copepod production, coinciding with a halving in copepod nauplii biomass, with a doubling in TA. These responses could be partly explained by the halving in large microplankton, an assumed preferred food source for copepods, detected right after treatment. However, none of these were sustained until the end of the experiment, thus suggesting no longer-term consequences. All in all, this study provides evidence for a low impact risk of enhanced TA on zooplankton, and ultimately the ES of food production. These findings set a promising stage towards the safe implementation of CO₂-equilibrated OAE in oligotrophic coastal waters. https://doi.org/10.5194/egusphere-egu23-15436 

• Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community. 

Altogether, the inadvertent effects of increased alkalinity on the coastal phytoplankton communities appear to be rather limited relative to the enormous climatic benefit of increasing the inorganic carbon sink of seawater by 21 %. We note, however, that more detailed and widespread investigations of plankton community responses to OAE are required to confirm or dismiss this first impression. https://doi.org/10.5194/bg-19-5375-2022

• Potential ecotoxicological effects of elevated bicarbonate ion concentrations on marine organisms. 

Recently, a novel method for carbon capture and storage has been proposed, which converts gaseous CO₂ into aqueous bicarbonate ions (HCO3¯), allowing it to be deposited into the ocean. This alkalinization method could be used to dispose large amounts of CO₂ without acidifying seawater pH, but there is no information on the potential adverse effects of consequently elevated HCO3¯ concentrations on marine organisms. In this study, we evaluated the ecotoxicological effects of elevated concentrations of dissolved inorganic carbon (DIC) (max 193 mM) on 10 marine organisms. We found species-specific ecotoxicological effects of elevated DIC on marine organisms, with EC50-DIC (causing 50% inhibition) of 11 -85 mM. The tentative criteria for protecting 80% of individuals of marine organisms are suggested to be pH 7.8 and 11mM DIC, based on acidification data previously documented and alkalinization data newly obtained from this study. https://doi.org/10.1016/j.envpol.2018.05.057 Conclusions The benefits for marine biota brought by the solution proposed by Limenet will have to be further deepened. However, given the preliminary studies in the literature, the assumptions seem very promising.

Life Cycle Assessment (LCA – Life Cycle Assessment) is an analysis methodology used to quantify the environmental impacts associated with a product, service or process throughout its life cycle, from the development of raw materials, the production, transport, use and end of life of the product or service. The main objective of LCA is to assess the environmental impact of the entire life cycle of a product or service, taking into account all the inputs and outputs of the system, and to identify critical points where action can be taken to reduce environmental impacts. Limenet SB has carried out a preliminary analysis of the LCA of its technology by making different case studies. This analysis was made in collaboration with the DICA department of the Politecnico di Milano. From this analysis it emerged that LCA, using renewable electricity is found between 6% and 10% (the difference depends on several factors). This means if LIMENET removes 100kg of gross CO₂, it is actually removing 94-90 kg of net CO₂. To see LCA

According to the IPCC, it will be possible to reduce CO₂ emissions by electrifying industrial processes and not by increasing from about 40 billion tons of CO₂ emitted worldwide in 2023 to about 8 billion emitted in 2050. Of these 8 billion we speak of emissions “hard to abate” or those emissions that can not be avoided. Think of heavy transport, aviation, metallurgical and chemical industries and much more. In order to have a carbon neutral economy, it will have to be expected that these 8 billion tons of CO₂ per year will be captured and stored in some way. The solution proposed by Limenet goes to attack these issues “hard to abate”. Considerations:

•  From an operational point of view, electricity must be used first to make industrial processes more efficient and reduce emissions, and secondly to capture and store CO₂ from the atmosphere.
• There are currently energy surplus locations in different parts of the world. Due to the temporal irregularity of renewables or their high presence in certain territories, there are periods of the year in which electricity is a surplus. This energy, if not used or stored, would be lost. Limenet is one of those technologies that can use it to store CO₂.

Calcium carbonate comes from geological deposits of calcite/dolomite/aragonite. The earth’s crust is composed of about 7% calcium carbonatei. The amount of calcium carbonate in the world could be enough to solve X times the problem of global warmingii. In the short term, calcium carbonate will be purchased by companies that extract the mineral respecting Limenet’s environmental policies. Figure 1 Calcium carbonate availability.

Unfortunately, few CO₂ capture and storage technologies exist in the world. The pioneering companies are: Climeworks, Carbon Engineering, Svante, Carbfix, Heirloom, Verdox, Seabound, Paebbl, Vesta, Carbon direct, 8 rivers, Carbyon, planetary, Sustera, Captura and a few others. Overall, in 2022 have together captured and stored about 20-40 thousand tons of CO₂ (to highlight the size of the market remember that the IPCC predicts that from now to 2050 must be captured and stored from the atmosphere on average 8-10 billion tons of CO₂/yrs) Every company with its technology must strive to scale its methodology to an industrial level that can remove a considerable amount of CO₂. The solution proposed by Limenet SB uses and exploits calcium bicarbonates in the sea as a CO₂ binding. This uniqueness allows:

• use of an alkaline substance to balance CO₂ before the alkaline substance enters the sea
• Introduction into the sea of a substance at the same pH as the sea

With this technology we want to contribute to the fight against ocean warming and acidification.

Given the industrial, chemical, technological and reporting complexities of Limenet carbon capture and storage technology, it was decided that, in order to give maximum monitoring and reporting quality, a monitoring protocol should be implemented, reporting and verification called MRV (Monitoring Reporting & Verification). This protocol, based on ISO 14064 Part 2, reports the additionality of the project and its effective removal of CO₂ (measured directly, industrially). In Limenet we started the road of realization of our MRV with the support of consulting companies Egenia s.r.l. Subsequently it will be verified by a third company. The MRV verification process will take place on the first TRL7 plant.

Limenet NFTs are digital certificates and should not be considered as speculative assets but as a different methodology to realize a certificate of negative emissions. NFT certification will be present in the MRV verification protocol.

In Limenet a credit is created after the industrial plant has stored the CO₂. Upstream of the removal of CO₂ there will have been the process of monitoring, reporting and verification of the industrial plant by a third party. Limenet will not act as a certifying body.

Limenet SB decided to implement a system of tracking negative CO₂ emissions through the blockchain. The motivation is to give transparency to the customer on the carbon certificate purchased by Limenet. Currently, the blockchain is used by other companies as a decentralized registry of information regarding the purchase or sale of CO₂ credits. In Limenet we have created a system for tracking the production chain of decarbonised hydroxide and then of the stored CO₂. If CO₂ comes from air or is a biogenic CO₂ (biogas), negative emissions are referred to. For example, starting from a batch of calcium carbonate and biogenic CO₂, we trace its transformation into decarbonised calcium hydroxide and then into negative CO₂ emissions. This, once certified, becomes an NFT with inside all the industrial information related to its realization. The customer who buys the NFT can check on the blockchain all the information related to its negative CO₂ emission: from what raw material was produced, to where it was processed, how much electricity it used etc. The final added value is to give the customer more information about the negative CO₂ certificate. Not only will you know that the certificate is verified by a third party but you will also have detailed information about how it was done.