New methods help integrate renewable hydrogen with waste CO2 to produce clean fuels

In Colorado, a National Renewable Energy Laboratory duo known for pushing the limits of power-to-gas is innovating another direction for renewable hydrogen, focused on upcycling carbon waste streams into key energy products. The NREL team is focused on tightly integrating two processes—renewable hydrogen production and downstream chemical reactions—to cut the capital costs and improve the efficiency of the overall process. Along the way, they are demonstrating novel approaches that will aid in decarbonizing our energy system.

NREL has developed and licensed aspects of its intellectual property for integrated hydrogen production; altogether, the innovations could reduce system electrolyzer costs by 5%–10%. For example, one recent NREL innovation uses the electrolyzer current (and therefore the rate that hydrogen is produced) to control the downstream ratio of hydrogen when mixed with other feedstocks, like carbon dioxide, for precise process control. Another improves the efficiency of reactions by injecting more soluble “wet” hydrogen, which has not passed through any of the drying stages present in commercial electrolysis systems. By scrapping the drying infrastructure, a utility-scale electrolyzer project could avoid tens of thousands of dollars in superfluous equipment and substantial losses in efficiency to dry the gas for non-transportation end-uses.

The flagship application of Dowe and Harrison’s integrated hydrogen/waste-to-energy machinery is to produce renewable natural gas (RNG). The process uses proprietary microorganisms provided by Electrochaea GmbH to metabolize hydrogen and waste carbon dioxide (CO2) into methane, a more sustainable replacement for fossil natural gas. As existing carbon markets incentivize RNG, other early-stage companies are exploring the full impacts of integrated hydrogen.