Laboratory investigates innovative technologies for capturing and using CO2

A newly inaugurated space at Poli-USP seeks to create more sustainable and economical high-pressure alternatives

The traditional processes for capturing and transforming carbon dioxide (CO₂), which is the main cause of global warming and climate change, must be updated. This is the opinion of Claudio Oller, Full Professor in the Department of Chemical Engineering at the Polytechnic School of the University of São Paulo (Poli-USP) and Coordinator of the recently inaugurated High-Pressure Laboratory, which operates there. One of the focuses of the laboratory, which is a part of the Research Centre for Greenhouse Gas Innovation (RCGI), is to create more sustainable and economical alternatives for this purpose via the use of high-pressure chemical and biological processes.

Among the ongoing initiatives is the Bioconversion Project of CO₂ in a supercritical state by bacteria from Antarctica, led by Oller. “In the laboratory, we work with sediments from the bottom of the Antarctic Sea, which are formed by the abrasion of glaciers with continental rocks and are rich in microorganisms, such as bacteria, some of them up to 20,000 years old,” says Oller. This material was collected by one of the Project’s researchers, Arthur Ayres, a Professor at Fluminense Federal University (UFF) and a participant in the Brazilian Navy’s Antarctic Program (PROANTAR).

In the laboratory, those sediments will undergo a series of tests, some of them in reactors especially developed for the Project. “The objective is to verify how these microorganisms behave under extremely large pressure variations, without light and in the presence of CO₂ in a supercritical state, which is a special state ranging between liquid and gas, obtained by means of high pressure,” Oller adds.

These extreme conditions are also found in underground sea caves that will be built in the Brazilian pre-salt levels and used to store CO₂ resulting from oil production. Thus, CO₂ is stored in a supercritical state so as to have a smaller volume in the salt caves. “This is one of the most effective ways to reduce greenhouse gas emissions, but it is not yet known what long-term effects these CO₂ reservoirs could have on the environment, not to mention the risk of leakage,” says Oller.

The Researcher points out that prospecting for these microorganisms in the laboratory can contribute to finding a solution for storing CO₂ in deep caves. “In the future, the microorganisms, which have an enormous capacity for metabolizing CO₂, could be injected into these reservoirs. The objective is for them to transform CO₂ from a supercritical to a solid state, which would prevent leakage. In addition, they could generate other products from CO₂, such as hydrocarbons and alcohol. In the laboratory, we are investigating both the scientific and the economic feasibility of this process.”

Another Project that will be developed in the laboratory is New technologies for CO₂ capture: deep eutectic solvents (DES) for CO₂ capture and nanostructured materials for gas separation (advanced materials for membranes). “The key word of this Project is selectivity: our objective is to attempt to improve the CO₂ capture filters that are already being used by industries. The reason for this is that to transform CO₂ into other raw materials, such as alcohol, the carbon needs to be pure,” explains Caetano Rodrigues Miranda, a Professor at the Physics Institute of the University of São Paulo (IF-USP) and one of the Project’s Coordinators.

Miranda explains that the Project works from two different angles, “They attack the same problem in diverse manners.” One develops deep eutectic solvents (DES). Reinaldo Camino Bazito, a Professor at USP’s Chemistry Institute (IQ-USP) and also one of the Project’s Coordinators, states that “Today, the main CO₂ capture technology uses amines. However, this process involves substantial amounts of electrical energy. Another option is to use ionic liquids, but carbon synthesis is relatively expensive and is not always adequate for all cases. Hence the need to look for alternatives to improve this process, including from an economic standpoint.”

Bazito says that the purpose of the Project is to make the DES able to preferentially capture the CO₂ through high pressure. “To that end, we will use small polymers, on a smaller scale, as well as hyper-branched ones. Both are capable of causing enormous amounts of interaction with carbon,” adds the expert, who is a member of USP’s Green and Environmental Chemistry Group. “This alternative is much cheaper than amines, for instance, because it does not require the use of substantial amounts of energy.”

Another angle of the Project is the development of membranes, through a process guided by computational modelling. Miranda explains that “The membranes function as filters that are capable of separating CO₂ and other gas molecules, such as nitrogen, which are then retained in these membranes. They can work at either high or low temperatures, depending on the material forming the membrane. Another of the project’s objectives is to identify the best operating conditions for these materials.”

To understand the processes that take place at the molecular level, researchers will rely on technological tools. Virtual reality allows researchers to monitor the interaction between atoms and molecules in real time. “The Project heavily involves being able to create models to do simulations. For example, it is possible to select the priority material before moving on to the experiment, which is the most expensive part of the process. With this computational screening, it is possible to select the most important systems and those that deserve to be focused upon,” says Miranda.

According to specialists, both DES and membranes can be used in industries that are major CO₂ emitters, such as steel, cement, and sugarcane mills. Miranda states that “Each of these options has specific applications and we must assess which one of them best adapts to the company’s reality.”

The Project’s objective is to offer one more alternative for solving this problem, since the concentration of carbon dioxide in the atmosphere has been growing continuously and will likely increase further over the coming years,” says Bazito. “Once CO₂ has been isolated, it will be possible to move on to another phase in creating a virtuous circle, which is to transform carbon into other raw materials. but that phase will be developed by another Project within the RCGI itself. Our Project is a steppingstone for that to happen.”

With its multidisciplinary profile, the Project will likely last four years and involve a team of around 20 researchers from such areas as chemistry, physics, and product engineering. “It is an integrated approach,” says Bazito. Miranda agrees with him and stresses, “A crucial point of the Project and of the RCGI as a whole is the training of human resources, since this is an area of research in which Brazil still needs heavy investments. This investment is increasingly necessary for the planet’s well-being.”