CO2 capture, use, and storage systems present an alternative way for Brazil to mitigate the effects of climate change
Petrobras conducts carbon capture operations on its P-75 platform ship, anchored in the Santos basin
Petrobras
In the effort to contain global warming, a group of promising technologies has gained increasing importance. These systems, designed for carbon capture, utilization, and storage (CCUS), aim to reduce the concentration of carbon dioxide (CO₂) in the atmosphere and thereby mitigate the effects of climate change. Such systems are capable of separating carbon dioxide generated during the exploration, production, and use of fossil fuels and biofuels, or even capturing it directly from the atmosphere, and subsequently preventing its release by storing it for long periods in geological reservoirs underground or reusing it directly or indirectly in other products.
Four such projects, known by the acronym CCUS (Carbon Capture, Utilization, and Storage), are being readied for pilot-scale operations in Brazil during the coming months and are expected to be the first to operate at onshore facilities in the country. Petrobras, which already conducts CCUS operations on 23 of its offshore oil and gas platforms, has begun implementing a capture and storage system at its Cabiúnas natural gas processing unit, in Macaé, Rio de Janeiro.
Repsol Sinopec Brasil, a joint venture between Spain’s Repsol and China’s Sinopec oil corporations, is developing two projects that aim to reduce atmospheric carbon stock through direct air carbon capture systems. The initiative is a partnership with the Pontifical Catholic University of Rio Grande do Sul (PUC-RS) and the teaching, research, and technological development center Senai Cimatec, in Bahia.
In São Paulo, the Research Centre for Innovation in Greenhouse Gases (RCGI), a partnership between Shell Oil and FAPESP, plans to install a pilot CCUS plant at the Institute of Chemistry of the University of São Paulo (IQ-USP) next year to generate green methanol, a type of renewable fuel production that does not release pollutants into the air. To achieve this goal, the unit will use the CO₂ captured in the ethanol production process.
“Carbon capture plays a fundamental role in the energy transition,” says engineer and physicist Julio Romano Meneghini, RCGI’s science director. “The world urgently needs to stop depending on oil, natural gas, and coal. As long as this dependence exists, we need to capture and store the CO₂ emissions caused by using fossil fuels.”
Alexandre Affonso / Revista Pesquisa FAPESP
Systems based on carbon capture and storage are still a rarity worldwide. The International Energy Agency (IEA) listed 47 CCUS facilities in operation in 2022 with the combined capacity to remove 45 million tons of carbon dioxide (Mt CO₂) per year from the atmosphere, a very limited volume compared to the 37.4 billion tons of CO₂ of emissions per year coming from the energy sector alone. Taking into consideration only the announced projects, which total nearly 100, the IEA estimates that capture and disposal capacity will reach 1 billion tons by 2030, more than the total annual emissions from civil aviation, which the agency calculates to be around 800 Mt CO₂ (see Pesquisa FAPESP issue nº 337).
The agency estimates CCUS capacity will reach 6 billion tons of CO₂ by 2050. This volume represents almost three times the total Brazilian emissions in 2022, assessed at 2.18 billion tons of carbon dioxide equivalent (CO₂e), according to the Greenhouse Gas Emissions and Removals Estimation System (SEEG), the primary greenhouse gas (GHG) emissions monitoring platform in Latin America. Carbon dioxide equivalent is an international measure that establishes the equivalent global warming potential between all other GHGs (methane, nitrous oxide, and others) and carbon dioxide.
Petrobras has been excelling in this area, which could bring significant gains to its production process. In 2023, the oil company captured 17 Mt of CO₂, which was 27% of the total sequestered globally. The carbon is removed from the natural gas associated with the oil extracted from the company’s pre-salt wells. It is separated from the other gases present, such as methane, ethanol, and propylene, using membranes — one of four main separation techniques currently in use (see infographic) — then reinjected back into the wells. In addition to preventing CO₂ emissions, this process, called enhanced oil recovery, also increases oil extraction productivity.
Alexandre Affonso / Revista Pesquisa FAPESP
“Reinjection is a solution for meeting the company’s commitment to not release the carbon dioxide present in natural gas into the atmosphere, thereby producing low-carbon oil from the pre-salt fields,” says Mauricio Tolmasquim, director of energy transition and sustainability at Petrobras.
Petrobras separates and stores more than 97% of all CO₂ originating from the natural gas associated with the oil extracted from pre-salt wells. Since 2008, when it launched the program, the company has reinjected more than 53 Mt of CO₂ and plans to expand the operation to another seven oil platforms. The goal is to reinject 80 Mt by 2025.
In 2023, the company announced a CCUS pilot project at the Cabiúnas natural gas processing unit, in Macaé, where a CO₂ removal system is already in operation using a different technology, chemical absorption. Petrobras uses this system to prepare natural gas produced from the pre-salt, which is characterized by a high CO₂ content, for the market.
Today, the carbon dioxide sequestered in Cabiúnas is released into the atmosphere. With the pilot project, the gas will be compressed and transported through a 60-kilometer pipeline to the São Tomé saline aquifer in Quissamã (RJ), where it will be injected and stored. This operation is expected to begin operations in 2027 and, as a pilot project, will last for two to three years, with an annual injection of 100,000 tons of CO₂.
“The pilot project will allow us to establish the storage capacity of São Tomé, which has the potential to become one of the main CO₂ reservoirs in the Southeast region. It will also enable us to develop and test storage monitoring techniques and ensure no gas will escape,” details Tolmasquim.
The success of this initiative, he says, will be crucial for Petrobras to proceed with a project to install the country’s first commercial CCUS hub. If approved, the structure will consist of CO₂ transport pipelines linking the saline reservoir in Quissamã to other Petrobras oil and gas processing facilities in the state of Rio de Janeiro, such as the refinery in Duque de Caxias.
Sugar-energy and hydrogen sectors In addition to the oil and gas industry, Meneghini, at USP, believes the sugarcane and hydrogen sectors have the appropriate technical conditions for installing CO₂ capture and storage systems. Today, 80% of the world’s hydrogen production uses natural gas as an input. This is known as gray hydrogen (see Pesquisa FAPESP issue nº 333) because its manufacture results in the release of air pollutants. For every kilogram (kg) of gray hydrogen produced, 10 kg of CO₂ are emitted. “Capturing and storing part of the CO₂ resulting from this process allows emissions to be reduced to less than 4 kg of CO₂ per kilo of hydrogen created. This is what is classified as blue hydrogen,” notes Meneghini.
In the sugarcane sector, the greatest potential lies in fermenting sugarcane or corn to produce ethanol, which emits high-purity CO₂ into the atmosphere. High purity means that more than 90% of the gases released during the fermentation of sugarcane and corn are made up of carbon dioxide, which makes it easier to separate from other gases and compress.
Alexandre Affonso / Revista Pesquisa FAPESP
The technique is already common among corn ethanol producers in the United States, while in Brazil, the corn ethanol manufacturer FS has already announced its plans to build a pilot CO₂ capture and storage plant at its facility in Lucas do Rio Verde, Mato Grosso.
Research conducted by mechanical engineer Sara Alexandra Restrepo Valencia during her PhD studies at the University of Campinas (UNICAMP) evaluated the technical and economic feasibility of capture and storage processes in bioenergy facilities. The study was awarded the 2023 CAPES Theses Prize in the interdisciplinary category. According to Valencia, a plant that processes 4 Mt of sugarcane per year emits 0.5 Mt of CO₂ during the fermentation process. If the facility uses its waste to generate electricity, an additional 1 Mt of CO₂ is emitted per year.
The average cost for capturing high-purity carbon generated during fermentation and storing it at a distance of up to 100 kilometers from the plant, the researcher calculates, is US$30 per ton of CO₂. The CO₂ emitted in bioelectricity generation by the conventional steam turbine method is impure and requires the use of technologies to separate the CO₂ from other gases before compression, transport, and storage. Separation is required to facilitate the chemical reaction necessary to adequately solidify carbon dioxide in porous rock formations, which reduces the risk of gas escaping from underground storage. This doubles the average processing cost. “Capture and storage operations are expensive, and mill operators are not incentivized to bear this cost,” says Valencia.
For mechanical engineer Arnaldo Cesar Walter, Valencia’s PhD advisor, the sale of carbon credits could be an important incentive for implementing carbon capture and storage systems in Brazil. However, the country does not yet have a regulated carbon credit market. For biofuel plants, one source of revenue is the federal RenovaBio program, established in 2017, which generates one decarbonization credit (CBIO) for each ton of CO₂ avoided. The market value for one CBIO was around R$100 as of the end of March. Meneghini believes the economic feasibility of carbon capture and storage systems will also depend on government support and regulation for the technology.
The potential for using CO₂ as a raw material for other commercial products is still limited. Possible uses include the production of urea-based fertilizers and chemical products such as organic acids and methanol. RCGI researchers have developed and patented a process for generating green methanol that will begin experimental operations in 2025.
Chemical engineer Pedro Miguel Vidinha from IQ-USP, who is a participant in the project, says the process can use the CO₂ captured during ethanol production to produce methanol. CO₂ molecules are mixed with green hydrogen obtained from renewable energy sources in a chemical reactor, and then a catalyst the group patented is used to create a reaction that converts the CO₂ into methanol. Research on the catalyst produced an article in the Journal of CO₂ Utilization in September 2020.
The pilot plant will be installed at IQ-USP and will have the capacity to produce 1 ton of methanol per week. The economic viability study on the process will be conducted throughout the rest of the year. “It has a lot of potential, since green methanol is considered an alternative for decarbonizing the shipping industry,” says Vidinha. Danish shipping company Maersk has already ordered 18 methanol-powered ships from several global shipyards, the first of which went into operation in February. The company estimates that it will reduce carbon emissions by more than 80% using the new vessels.
Understanding capture and storage technology Carbon is stored in reservoirs more than 800 meters deep
There are already several mature, commercial technologies that can be applied to remove carbon dioxide (CO₂) from the atmosphere or from gas streams, such as those associated with oil. The four most common are chemical absorption, membrane separation, adsorption, and cryogenic distillation.
Regardless of the technique, after being separated from other gases, the CO₂ is subjected to temperatures above 32 degrees Celsius (°C), at a pressure of 7.38 megapascals (MPa), reaching the so-called supercritical state. Under these conditions there is an increase in the gas’s density, bringing it to a state close to liquid, reducing its volume and facilitating transport via pipelines, trucks, or ships to the storage site.
At that point, it will be injected into underground reservoirs and would be expected to remain in place for hundreds of years or even indefinitely. Potential storage locations include depleted oil and gas fields, saline aquifers, volcanic rock formations such as basalt, and sedimentary formations like sandstone, limestone, and rock salt, which have the requisite porosity and permeability for fluid absorption.
“The reservoir where the CO2 is to be deposited must be at least 800 meters deep. There, the gas will be subjected to pressure and temperature conditions capable of maintaining its supercritical state, hindering it from escaping and returning to the atmosphere,” explains geologist Colombo Celso Gaeta Tassinari, who conducts research at the Institute of Energy and Environment at the University of São Paulo (USP) and the Research Center for Innovation in Greenhouse Gases (RCGI).
Sealed with concrete After the reservoirs are filled, the wells that were opened for gas injection are sealed, normally with concrete. If there is a leak, the CO₂ will return to its gaseous state and the entire procedure would have been wasted.
Brazil has tremendous potential for carbon storage areas, both in terrestrial and oceanic reservoirs. The Paraná sedimentary basin alone, which spans a region from Mato Grosso to Rio Grande do Sul, could accommodate all the CO₂ generated in the South and Southeast regions. The sedimentary basins of São Francisco, Parnaíba, and the Amazon are also considered promising. Sedimentary basins are geological structures formed by several layers of sedimentary and volcanic rock.
Determining locations for installing reservoirs is made through geological and geophysical studies that can take four years or more. A reservoir with an area of 10 square kilometers can store a few billion tons of CO₂, observes Tassinari.
With the support of FAPESP, Tassinari is conducting a study on the geochemical and hydromechanical characteristics of geological CO₂ reservoirs in Brazil. He believes storing captured carbon is a necessity, since, according to the International Energy Agency (IEA) only 8% of the CO₂ that will be captured by 2070 is expected to be used for industrial purposes. “The other 92% will have to go into geological storage,” Tassinari says.
Projects 1. Research Center for Innovation in Greenhouse Gases (RCGI) (nº 20/15230-5), Grant Mechanism Engineering Research Centers (CPEs); Principal Investigator Julio Romano Meneghini (USP); Investment R$19,516,850.65. 2. Study of the geochemical and hydromechanical characteristics of geological CO₂ reservoirs based on geophysical monitoring of the processes of interaction between fluids rich in CO₂ and rocks – EHMPRES (nº 22/02416-9); Grant Mechanism Regular Research Grant; Principal Investigator Colombo Celso Gaeta Tassinari (USP); Investment R$164,754.94.
Doctoral thesis VALENCIA, S. A. R. Avaliação da viabilidade técnico-econômica de sistemas Beccs na geração de eletricidade com uso de biomassa residual da cana. University of Campinas (UNICAMP), 2022.
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