Bold claim: turning trash into treasure could reshape our energy future. Pore Choices: A fresh approach to capturing gas from waste streams.
Jessica Rimsza, a materials engineer at Sandia National Laboratories, believes there is untapped value in what many regard as waste. Byproducts from U.S. agriculture—food scraps, manure, and sewage—are not just waste; they’re rich sources of biogas, a mixture that includes methane and other useful chemicals. Rimsza and her Sandia colleagues are developing chemistry to pull methane from biogas and separate it from other gases so it can be put to practical use.
“We’re creating new types of porous liquids that can selectively capture methane and other gases,” Rimsza explained. “This could become a supplemental domestic energy source to help bolster U.S. energy independence.”
The technology holds promise for real-world biogas capture at wastewater treatment plants, farms, and other facilities that already generate biogas but may lack efficient methods to separate and upgrade it.
A liquid with built-in empty space
Porous liquids combine a liquid solvent with a porous solid material, producing a liquid that contains tiny cavities. Those cavities create empty space inside the liquid, allowing it to absorb and store gas molecules.
The porous solids can range from established materials like zeolites to newer, highly tunable structures such as metal-organic frameworks, covalent organic frameworks, and porous organic cages. By mixing different solids and solvents, researchers can tailor how the liquid behaves.
“As I like to say, gases dissolve in liquids all the time. That’s why fish can breathe—there’s dissolved oxygen in the water,” Rimsza noted. “With porous liquids, we add a solid with free space into the liquid, and when we preserve that free space, dissolved gases move into the material.”
The team has produced dozens of porous-liquid formulations already, and many more combinations are possible given the vast number of solids and solvents.
“There are hundreds of thousands of porous materials and tens of thousands of solvents, which means a huge, still-untapped pool of potential porous-liquid mixtures,” Rimsza said. “Even if a tiny fraction turns out to be useful, that could still yield thousands of viable combinations.”
Separating methane from the mix
Rimsza’s current focus is porous liquids that can selectively capture methane from biogas, separating it from carbon dioxide and other impurities.
“The gas has to travel from the air into the solvent, and then from the liquid into the empty spaces inside the pores,” she explained. “That creates multiple choices for selecting what gets captured. It’s like stacking levels of sieves.”
Once captured, methane can be released from the porous liquid and used for electricity generation, heating, or as a feedstock for making hydrogen, methanol, ammonia, and acetylene—chemicals used in fertilizers, plastics, and other products. In earlier work, the team designed porous liquids that selectively capture carbon dioxide for applications in soft drink production and beyond.
Rimsza suggested the liquid form could simplify integration with existing infrastructure.
“As a liquid, they can be fed through standard piping, unlike solid porous materials that require specialized handling and setup,” she said.
From theory to today’s research
Porous liquids emerged relatively recently. They were first theorized in 2007 and demonstrated in 2015. Sandia’s research broadens the possibilities of these materials for energy applications by characterizing behavior and testing new combinations that maximize gas absorption and selectivity.
Researchers are also exploring how much gas porous liquids can capture. In some formulations, porous liquids hold more gas than the individual components would on their own.
For example, a typical solvent might accommodate about 1% gas, and a porous solid up to 80%. When combined into a porous liquid, the capacity can exceed simple additive expectations, sometimes by as much as 40 times, even when solid material accounts for only about 10% of the weight. This synergistic effect can dramatically boost gas uptake.
The team has filed a broad patent covering the definition and design principles of porous liquids and has published numerous journal articles on the topic. The work is supported by the Department of Energy Office of Science Basic Energy Sciences program and Sandia’s Laboratory Directed Research and Development program.
This material is based on information from Mirage.News and the authors’ findings, shared for public awareness of ongoing research in energy materials.
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