LightNET Carbon Capture CO₂atings and CO₂rallites: A circular ex-situ mineralization route for CO₂ capture, sequestration, and product valorization

Mitigating climate change at a global scale is a huge challenge whereas the time for the necessary societal transformation is short. Despite all our recent efforts, during the past years, we have been emitting worldwide ∼17Gt CO₂/year in excess to the atmosphere.¹ This has been translated into a steady increase in CO₂ concentration in the atmosphere, which has reached 419,2 ppm in 2023 (50% more of the pre-industrial levels).² There are natural sinks for CO₂, such as land and oceans, which fix CO₂ through natural weathering in a global phenomenon known as the carbon cycle. However, this natural balance has been altered by our recent anthropogenic CO₂ emissions: Historical data as well as future climate models show that global warming is (approximately) directly proportional to the increase in CO₂ concentrations in the atmosphere. More specifically, every time the CO₂ concentrations rise by 10 ppm, the mean global temperature increases by 0.1 °C.³ Therefore, there is an urgent need to develop technologies to adapt, mitigate, or reduce CO₂ emissions to meet the planetary climatic goals.

The human response options to climate change⁴ are currently focused on the following.

• Indirect solutions: solutions oriented to adapt our cities, forest, and rural ecosystems or actions to mitigate CO₂ emissions along all the productive chain: (1) adaptation (e.g., making cities more resilient to heat waves and depleting of coastal regions due to sea level raising etc.) and (2) mitigation (e.g., renewables and electrification).

• Direct solutions (CCSU—Carbon Capture and Storage Use): solutions oriented to directly tackle the CO₂ emission either by capturing CO₂ at the emission point (industry) or directly from the atmosphere. (3) To avoid CO₂ to be released at the atmosphere at the emission point or point source CO₂ capture (PSC) and (4) to capture CO₂ directly from the atmosphere once emitted or negative emission technologies (NET) (e.g., direct air CO₂ capture (DAC)).

To reduce carbon dioxide emissions into the atmosphere from industries, carbon capture and sequestration (CCS) technologies have been used since the 1970s. CCS involves the capture of CO₂, generally from large point sources such as power generation or industrial facilities that use either fossil fuels or biomass as fuel. If not being used on-site, the captured CO₂ is typically compressed and transported by pipeline, ship, rail, or truck to be used in a range of applications or injected into deep geological formations, such as depleted oil and gas reservoirs or saline aquifers.⁵ As an initial step, the different technologies for CO₂ capture relies on materials with selective absorption or adsorption CO₂ properties,⁶ e.g.: (1) chemical absorption: using liquid ammonia, amine blends, ionic liquids, and aqueous alkanolamines; (2) physical absorption: using Rectisol^TM, Fluor, or ionic liquids; (3) chemical adsorption: using amine-based adsorbents, metal oxides, and alkali metal-based materials; and (4) physical adsorption: using zeolites, silica materials, and metal-organic frameworks (MOFS). Other methods include inorganic polymeric membranes and cryogenic methods based on distillation or anti-sublimation. Among these materials, some solid oxides such as MgO and CaO undergo carbonation in the presence of CO₂ and form stable carbonates. This chemical reaction is considered a carbon capture and storage technology since CO₂ is permanently fixed under ambient conditions.⁷  Regarding the final fate of the captured CO₂, in situ mineralization involves the transportation of CO₂ to a site where it is permanently injected into rock formations, the likes of saline aquifers or depleted oil and gas reservoirs. Alternatively, ex-situ carbon mineralization pathways can be developed where the captured CO₂ is mineralized into carbonates or engineered processes such as concrete. Carbon capture and utilization (or use) (CCU)—instead of just storing the CO₂ permanently—focusses on reusing it from industrial processes by converting it into goods such as biofuel, plastics, industrial fluids, or others. CCS projects worldwide have considerably increased in the past years. The Global CCS Institute counts 196 CCS current facilities in the world (2022)—including 30 projects in operation, 11 under construction, and 153 in development—with a total capacity of 243,9 Mtpa (representing a 44% increase from previous year).⁸ According to Bloomberg, CCS reached $6.4 × 10⁹ in global investment in 2022.⁹ 

LightNET Carbon Capture S.L. (LNCC) develops several products for sequestering and valorizing CO₂ from industries and/or directly from the air. One of the common themes across the different CCS technologies is the role of inorganic solid carbonate transformations using anthropogenic CO₂ and the development of predictive controls over these pathways. CO₂ generated from power plants or industrial sources can be captured, compressed, and stored in reactive geologic formations where CO₂ in its fluid form mineralizes to produce water-insoluble calcium or magnesium carbonates, in a process known as in situ carbon mineralization. The availability of Ca- and Mg-bearing resources is crucial for implementing carbon mineralization pathways. About 10 000–1000 000 Gt of total carbon can be stored in naturally occurring mineral deposits. The US Geological Survey reports that resources from which calcium compounds can be recovered range from large to virtually unlimited and are globally widespread.¹⁰ Accounting ∼100 × 10⁶ tons, limestone represents up to 42% of all the quarry products in Catalonia and Spain.¹¹ Other sources of Ca-oxides such as gypsum (CaSO₄·2H₂O) or dolomite CaMg(CO₃)₂ represent 9% and 5% of the total, respectively. In addition, there are many natural and industrial waste sources of alkalinity (e.g., CaO, MgO, and Na₂O) that could be either deployed or weathered to remove CO₂ from flue gases or from air. The key advantage of the proposed scheme is, therefore, that the required materials are locally available at low cost.¹² 

Our solution is inspired by nature but more efficient, accelerated ex-situ mineralization. On top of mindful greenhouse gas reduction efforts and increasing use of renewable energy, attention is turning to feasible carbon dioxide removal methods (CO₂ carbon capture) that target CO₂-material reactions by both in situ and ex-situ surface and sub-surface approaches, collectively termed geochemical CO₂ removal strategies. One of the main principles is to induce or accelerate the natural chemical weathering reaction to form soluble bicarbonates (stabilized primarily by Ca²⁺, K⁺¹, or Mg²⁺ cations), i.e., alkalinity, or to later precipitate solid carbonate minerals. These reactions can remove CO₂ from the atmosphere and store it safely for 100s of thousands of years or longer, but are slow processes, taking similar timescales to occur in nature. LNCC ex-situ CO₂ removal strategies are focused on speed up reactions to occur on human timescales of several decades or faster to meet long-term international climate targets.

We have developed innovative material solutions that can be turned into products that will capture CO₂ at a faster rate and efficiency than current point source capture (PSC) and direct air capture (DAC) absorbers. Here, we present the following products (TRL 6-7) from our catalog (Fig. 1): (1) CO₂ating^®: a coating layer for any kind of surface that captures CO₂ until its saturation. (2) CO₂rallite^®: a replaceable element that captures CO₂ until its saturation and then may be replaced. Potential markets for products and subproducts of LNCC include (elaborated) raw materials sector, construction sector, chemical sector, environmental sector, CCSU Sector, food sector, pharmaceutical sector, agricultural sector, education sector, other industrial sectors (cement, paper, paints, rubber etc.), and administration (EU, national, regional, and local). As a service, tailored CO₂rallites may be embedded in larger systems to be replaced as systems to capture CO₂ at the emission point (PSC).

LNCC products are based in elaborated raw materials, which may carbonate (capturing CO₂) and are locally available, earth abundant, and non-toxic. The sources of these raw materials may be diverse, including mining or quarries, but may also come from raw or processed (agro, industrial, domestic etc.) waste or thermal, chemical, or electro-chemical sub-products either from solids (e.g., rocks) or liquids such as seawater. This baseline material is able to capture CO₂ either by using an adsorption or absorption process with certain efficiency. The CO₂ baseline process is based in the conversion of certain materials (primarily oxides/hydroxides) into carbonates in the presence of carbon dioxide. Additives, excipients, or catalyzers may be incorporated to increase the CO₂ capture efficiency (rate, velocity, and % in weight). The additives may also add certain aspects to the final product, such as specific chemical composition, further mechanical resistance, color, or light sensitivity. Our toolkit has several unique deep-tech scientific competitive advantages including the CO₂ capture enhanced by sunlight. Characteristic CO₂ saturation time [Fig. 2(b)]/70% max capacity) depends on several factors, e.g., CO₂ concentration (ppm), temperature, and humidity. Owing to Fick’s law of diffusion,¹³ typical direct air capture (DAC) characteristic times are in the range of 5–10 days (420 ppm), while it is in the range of minutes for point source capture (typically, 1%–10%). To mitigate techno-economic bottlenecks, LightNET Carbon Capture focuses on four innovation areas along the entire value chain, i.e., (i) origin/activation of raw materials (circular economy of industrial waste), (ii) CO₂ating and CO₂rallite rate/efficiency enhancement (nanotechnology, chemistry, and material science applied to CO₂ capture), (iii) product/market fit (development of new climatic products and markets), and (iv) CO₂ valorization (valorization of sub-products containing mineralized CO₂).

Urban spaces cover about 3% of the land on Earth, yet they produce about 72% of all global greenhouse gas emissions. On top of that, cities are growing fast; in Europe, it is estimated that by 2050, almost 85% of Europeans will be living in cities.¹⁴ Therefore, the climate emergency must be tackled by cities—and by citizens. It is virtually impossible to implement current NET or DAC solutions into cities because their inherent lack of space (the removal of a single Barcelona citizen CO₂ footprint would require 500 trees) or because their variety and instability of geological substrates. Lined-up with new ideas such as Skidmore, Owings and Merrill (SOM) “Urban Sequoia^TM”—a concept for buildings and their urban context to absorb carbon at an unprecedented rate,¹⁵ LighNET could add climate negative aspects to any urban space. As an example, just 3 m² of LightNET CO₂rallite in urban furniture will capture in ten days the same CO₂ as a mature tree in one year. The LNCC objective is to establish the capabilities for sequestrating 100 000 tons of CO₂ by 2029. The LNCC solution could be then offered to local admins and can be easily scaled-up to work as a “CO₂ waste collection” to sequestrate, e.g., the 5%–10% of Barcelona emissions by 2030 and even, according to predictions, to potentially solve its entire emission problem by 2035.

LightNET Carbon Capture has been collaborating with Spanish global building companies to validate a solution for capturing CO₂ from building surfaces. In particular, a test was conducted on temporary structures in a new building complex near Barcelona city, effectively simulating the real conditions and environment of a construction site. In this pilot test, the CO₂ absorption capacity was assessed as a function of the orientation of the facade on which it was applied [Fig. 2(a)]. To accomplish this, the CO₂ating mortar was applied to four facades with varying orientations (north, south, east, and west) and periodic samples of the substance were collected for a month. This innovative mortar has been proven to be an effective alternative and offers significant advantages:

• It is possible to obtain it from earth-abundant raw materials and industrial waste.

• It has an aesthetic surface without cracks.

• Even immediately after application, it can withstand rain and moisture.

• It is compatible with various building materials, including Portland cement, concrete, and asphalt.

• Zero energy consumption, high speed, and CO₂ capture efficiency.

• It presents an opportunity to promote the circular economy and the use of building materials with a lower environmental footprint.

In contrast with geological injection (which are usually big facilities located on depleted gas/oil reservoirs) or the inherent problems of monitoring CO₂ capture in living platforms (timescale, difficulty of measurement etc. ), LNCC is perhaps the only NET technology that can be straightforwardly manipulated and measured. Any increase in weight of a CO₂rallite comes from captured CO₂ at a reason of ∼1% per day. That means, e.g., only 50 g of CO₂rallites can be monitored using non dedicated lab equipments such as a kitchen scale. An example of this easy deployment as an educative platform is the Fundacio Catalana de la Recerca i Innovació (FCRi) initiative “Llença la pedra i amaga el CO₂”¹⁶ in the framework of the Catalan Science Week 2023. In this public engagement with science in schools, over 70 schools distributed along Catalonia have monitored this weight increase depending on basic environmental parameters, such as humidity, indoor/outdoor, sunshine etc. This successful hands-on experiment will ignite the awareness of climatic change impacts and the need of negative emission technologies among the youngest if the climatic goals are going to be accomplished.

The present technology has its basis on the previous patent: method to photo-capture CO₂ with perovskite oxide compounds or oxide compounds. The present patent application relates to a method to photo-capture CO₂ with perovskite oxide compounds or oxide compounds. Application Publication/Patent Number: EP4084890A1. Publication date: 2022-11-09. Application number: EP20839361.1 Filing date: 2020-12-30. Inventors: Perez, Tomas Amador; Rubio, Lorente Carles; Sauthier, Guillaume; David, Jeremy; Vales, Castro Pablo; Arbiol, Cobos Jordi; Santiso, Lopez Jose; and Catalan, Bernabe Gustau. Assignee: Fundació Institut Català de Nanociència i Nanotecnologia (ICN2) Institució Catalana De Recerca I Estudis Avançats (ICREA). Status: Granted, into the national phases. To strengthen IP protection, we did a study with CLARKE and MODET to define our IP protection strategy along the further definition and development of the potential final market product, including the protection of the know-how not included in the patent and future industrial processes that would be needed to bring the technology to the market. To further validate the IP strategy and identify potential market barriers, we did a freedom to operate (FTO) study with ZBM Patents to identify potential patents that we could infringe in the definition of our commercial products based on the patent or in the required industrial processes. No patent was identified in US and Europe markets that could block us for commercialization. An industrial secret was legally issued for protecting all the recipes for the fabrication of CO₂atings and CO₂ralites, including type and origin of raw materials, additives, fabrication methods, and recipes. The names of products CO₂rallites and CO₂atings are being registered too. The legal owners of the technology are LigthNET Carbon Capture S.L., the Catalan institute of Nanoscience and Nanotechnology (ICN2) and the Consejo Superior de Investigaciones Científicas (CSIC).

LNCC specializes in ex-situ CO₂ removal strategies, targeting accelerated reactions within human timescales to meet long-term international climate goals. Our innovative material solutions outpace current point source capture (PSC) and direct air capture (DAC) technologies, offering products that capture CO₂ more efficiently (CO₂ating, CO₂rallite, and CO₂filter^®). These products, based on sophisticated raw materials, sourced from diverse channels (mining, quarries, and waste streams) find applications across diverse sectors, including raw materials, construction, chemical, environmental, CCSU, food, pharmaceutical, agricultural, education, and various industrial sectors. LNCC is at the stage of validation of business models to test and to tune initial assumptions about target markets, value proposition, and product and service fit. The new and patented material science is only one of the main aspects of LNCC; circular economy from the cradle to grave, engagement with Catalan and Spanish industry, rural realities, and urban waste management for further valorization of the captured CO₂.

We acknowledge Escola Pia de Sitges, Sitges (Núria Mestre Pérez); Escola Pau Casals, El Vendrell (Aurora Ventosa Calbet); INS Bosc de la Coma, Olot (Ferran Pellicer Rodríguez); and Institut Escola Greda, Olot (Marta Cullell Busquets) for providing materials for this publication.

We also acknowledge Institut Josefina Castellví i Piulachs, Viladecans (Raquel Campos Castán); INS La Sureda, Palafrugell (Sara Gabarrón, Meritxell Cruañas, Oriol Colldecarrera); INS Cubelles, Cubelles, (Ana Ponce León, Elisenda Vidal Sans); Fundación Educativa Amor de Déu, Sant Adrià de Besòs, (Luis Jalón Hidalgo); Escola Consol Ferré, Amposta (Sandra Solà); Escola Bergantí, El Masnou (Toni Garcia); Escola Eladi Homs, Valls (Goretti Andreu); Escola Paidos, Sant Fruitós de Bages (Isabel Morraja Leiguarda); INS Alexandre de Riquer, Calaf (Ariadna Segura Duch); Escola Vilanova de Segrià, Vilanova de Segrià (Alícia Morlans Ballesté); Escola Josep Barceló i Matas, Palafrugell (Ruben Vargas Quiñones); Institut Alt Foix, Sant Martí Sarroca (Isabel Moreno Verbo); Col·legi Vedruna Santa Coloma de Queralt, Santa Coloma de Queralt (Maria Teresa Soler Casellas); Institut de Deltebre, Deltebre (Aida Fibla Tomàs); Institut Puig Castellar, Santa Coloma de Gramenet (Carolina Saniger Merino); Institut La Ferreria, Montcada i Reixac (Manuel Serafín Ramiro Trenado); Col·legi Les Savines, Cervera (Edgar Rodero Roig); Col·legi Sant Josep, Reus (Mercè Civit Salvat, Isidre Torroja Capdevila); Escola El Rajaret - ZER Montgrí, Bellcaire d’Empordà (Lluïsa Piferrer Morer); Institut Escola Greda, Olot (Marta Cullell Busquets); Col·legi Vedruna Manlleu, Manlleu (Ingrid Vilalta Rovira); Institut Can Mas, Ripollet (Cira Garcia Ros); Escola Catalunya, Sant Adrià de Besòs (Dina Frias); Institut Miquel Martí i Pol, Cornellà de Llobregat (Maria Belmonte); FEDAC Guissona, Guissona (Rosa M Morros Vives); Institut Gelida, Gelida (Rosa Perarnau Ramos); INS Terra Alta, Gandesa (Núria Gisbert Bueno); INS Vilamajor, Sant Pere de Vilamajor, (Irene Fraile Torroella); Institut Pons d’Icart, Tarragona (Cristina Arqué); Institut Vacarisses, Vacarisses (Dulcenombre Medina López); IE Caritat Serinyana Cap de Creus, Cadaqués (Marina Fortea Esparza); INS Anton Busquets i Punset, Sant Hilari Sacalm, (Josep Broch Muñoz); Escola Pi Verd, Palafrugell (Ernest Serra Soler); Institut de L’Arboç, L’Arboç (Mercè Pagan Polo, Maite Morales Secanella); Escola Els Roures - ZER Gavarresa, Sant Feliu Sasserra (Cèlia Soldevila); Institut Pere Barnils, Centelles (David García); INS Poeta Maragall, Barcelona (Àngel Pérez Beroy, Susana Colomer Domènech); Col·legi Vedruna Cardona, Cardona (Mercè Boixadera de León), IES Can Peixauet, Santa Coloma de Gramanet (Daniel Ramil Ramos); INS Pobla de Segur, La Pobla de Segur (Montse Martínez Palacín); INS Santiago Sobrequés i Vidal, Girona (Mian Vich Homs); Institut Bisbe Berenguer, L’Hospitalet de Llobregat (Núria Sanz Casañas); Ins Lacetània, Manresa (Marta Santaulària Rosell); Institut Jaume Salvador i Pedrol, Sant Joan Despí (Xavier Monje Vega); Institut Sant Pere i Sant Pau, Tarragona (Ester Borrell); Institut Berenguer d’Entença, L’Hospitalet de l’Infant (Jaume Espuny Casademunt, Lourdes Gil Pagà); INS Vescomtat de Cabrera, Hostalric (Montse Jordà, Maria Tomàs i Vives); Escola l’Alzina, Molins de Rei (Luis Garrido Bujardón); Institut Guillem de Berguedà, Berga (Ferran Barroso Boixader); Escola Mont-roig, Balaguer (Cristina Carbonell Figuerola); Escola Sant Vicenç, Mollet del Valles (Montse Farell Pastor); Escola Consol Ferré, Amposta (Sandra Solà); INS Montgrí, Torroella de Montgrí (Conxi Camúñez Garcia); Institut del Voltreganès, Les Masies de Voltregà (Anna Folch Albareda); Sant Antoni Maria Claret, Cornellà de Llobregat (Rosalia Donaire Pena); Escola El Rajaret - ZER Montgrí, Bellcaire d’Empordà (Lluïsa Piferrer Morer); Bernat Metge, El Prat de Llobregat (Olga Ruiz Mariscal); Escola Marjal, Les Cases d’Alcanar (Joel Roig Fornós); Escola Santa Caterina, Vinyols i els Arcs (Anna Escudé Recasens); Les Eres, Vinebre (Miguel Segura Caelles); FEDAC Súria, Súria (Manoli Garcia Soler); Escola Mare de Déu de la Roca, Mont-roig del Camp (Ernest Frigola Olives); Institut Sunsi Móra (Canet de Mar); Eulàlia Salichs Fradera; Ins El Pont de Suert, El Pont de Suert (Ester Parache Palacín, Cristian Fondevilla, Arnau Pueyo); Escola Sant Joan, Berga (Mònica Corominas Camprubí); and Institut Martí Pous, Sant Adrià, Barcelona (Anna Saperas Morón) for participation and feedback on LightNET - Fundació Catalana per a la Recerca i la Innovació (FCRI) Setmana de la Ciència (2023). We thank Salva Ferré and Bea Cordero from EDUSCOPI (Agència de Comunicació Científica) for composing the didactic materials. This work was partially supported by grants ajuts d’Indústria del Coneixement under Grant Nos. (IdC) AGAUR INNOVADORS 2023 (INNOV 00069) and IdC AGAUR PRODUCTE 2024 (Professor 00147 METHAFILTER); Grant Nos. AGAUR SGR 2021_SGR_00496, AGAUR SGR 2021_SGR_00457 and ACCIÓ innovació oberta i disruptiva; Grant No. ACE139/24/000076, funded by the Generalitat de Catalunya. Colaboración Público-Privada (Programa CSIC COCREA-CONVERGE) Convocatoria 2024 COCRE24034 (ESCO2RIAS). Maria de Maeztu; and Grant No. CEX2023-001397-M funded by Grant No. MICIU/AEI/10.13039/501100011033. ICN2 is funded by the CERCA programmme/Generalitat de Catalunya and by the Severo Ochoa Centres of Excellence programme under Grant No. CEX2021-001214-S.

The authors have no conflicts to disclose.

Amador Pérez-Tomás: Conceptualization (lead); Data curation (lead); Formal analysis (lead); Funding acquisition (lead); Investigation (lead); Methodology (lead); Project administration (lead); Supervision (lead); Validation (lead); Visualization (lead); Writing – original draft (lead); Writing – review & editing (lead). Pedro Pastor-Andreu: Conceptualization (supporting); Data curation (lead); Formal analysis (equal); Funding acquisition (supporting); Investigation (equal); Project administration (supporting); Supervision (supporting); Writing – original draft (supporting); Writing – review & editing (supporting). Marina Bujaldon: Data curation (supporting); Formal analysis (supporting). Àlex Argemí: Funding acquisition (equal); Project administration (supporting). Claudia Nieva: Conceptualization (equal); Funding acquisition (equal). Jordi Arbiol: Funding acquisition (supporting); Methodology (supporting); Resources (equal). Eugènia Riqué: Project administration (supporting); Resources (supporting); Supervision (supporting); Validation (supporting). Jordi Mas-Castella: Conceptualization (supporting); Funding acquisition (supporting); Investigation (supporting); Methodology (supporting); Project administration (supporting); Resources (supporting). Enric Garrell: Funding acquisition (supporting); Investigation (supporting); Methodology (supporting); Project administration (supporting); Resources (supporting). Francisco Negre Medall: Conceptualization (lead); Formal analysis (lead); Funding acquisition (lead); Investigation (lead); Project administration (lead); Supervision (lead).

The data that support the findings of this study are available from the corresponding author, APT, upon reasonable request and commercial restrictions.