PFI-RP: Low-Pressure Storage and Separation of Carbon Dioxide and Methane in Biogas to Enable the Use of Renewable Sources

The broader impact/commercial potential of this Partnerships for Innovation - Research Partnerships (PFI-RP) project is a system that enables the creation of next-generation fuel storage/delivery tanks that permit vast areas of the U.S. transform biowaste (biogas) into commercially-important, renewable natural gas on a larger scale. There is a pressing need to replace automotive fossil fuels with renewable fuels. One immediately realizable step in the U.S. is to tap into renewable natural gas of variable grades from biowaste as well as renewable hydrogen from surplus electricity. Low-pressure storage can deliver these fuels to natural gas vehicle operators nationwide, even when off the natural gas grid. This project provides both fundamental insights into low-pressure onboard gas storage and the processes and protocols that permit a system to optimally function on demand both as a fuel storage/delivery system and as a gas separator. The project enables municipalities to use biogas even when they do not have a pipeline-grade renewable natural gas (removal of carbon dioxide) processor or the ability to compress natural gas to fueling-station pressures. The project also enables communities to market locally produced renewable energy. The project seeks to develop, demonstrate, and bring to the marketplace a natural gas tank that can be configured as a dual, on-demand gas storage and separation system for storage and delivery of fuels. The tank will also perform on-board separation of carbon dioxide from low-grade renewable natural gas to generate high-grade renewable natural gas. The gas tank design will fill a critical knowledge gap in the detailed understanding of the adsorption of mixtures into porous materials. The team proposes to build an experimental, theoretical, and computational framework that will lead to new design principles for optimal storage, delivery, and separation of gases in conditions similar to what is expected in a vehicle. Extensive multi-component 3-dimensional (3D) adsorption isotherm surfaces will be studied experimentally and computationally to obtain performance metrics for different materials and adsorption/desorption cycle paths. The team also seeks to understand the behavior of co-adsorbing gas mixtures and their interaction with adsorbents. The project seeks to: create laboratory models of gas storage/separation systems by investigating co-adsorption of mixtures producing 3D isotherms, establish kinetic benchmarks for their desorption, identify optimal protocols for gas storage and separation, and demonstrate a system on a prototype automotive tank, including multiple fill/empty/separation cycles, assessing tank regeneration procedures. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.