Producing carbon nanofibers from ambient carbon dioxide seems like a potential breakthrough. You are removing the greenhouse gas from the air, and producing an incredibly useful product that can be used for everything from batteries to store renewable energy (discussed in this article) to (I am speculating) strong, light-weight carbon-negative materials that could replace a portion of the heavy-footprint steel and concrete we use today.

Carbon Nanotubes Produced from Ambient Carbon Dioxide for Environmentally Sustainable Lithium-Ion and Sodium-Ion Battery Anodes

The cost and practicality of greenhouse gas removal processes, which are critical for environmental sustainability, pivot on high-value secondary applications derived from carbon capture and conversion techniques. Using the solar thermal electrochemical process (STEP), ambient CO2 captured in molten lithiated carbonates leads to the production of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) at high yield through electrolysis using inexpensive steel electrodes. These low-cost CO2-derived CNTs and CNFs are demonstrated as high performance energy storage materials in both lithium-ion and sodium-ion batteries. Owing to synthetic control of sp3 content in the synthesized nanostructures, optimized storage capacities are measured over 370 mAh g–1 (lithium) and 130 mAh g–1 (sodium) with no capacity fade under durability tests up to 200 and 600 cycles, respectively. This work demonstrates that ambient CO2, considered as an environmental pollutant, can be attributed economic value in grid-scale and portable energy storage systems with STEP scale-up practicality in the context of combined cycle natural gas electric power generation.

Combined with renewable energy sources, maybe this is the breakthrough technology that gets us over the current hump where we are pushing against the ecological limits, and sets us on a path of continuing growth with a lower footprint until we eventually push against the limits again. Or, put the right incentives and policies in place to control the unsustainable portion of the growth, and with this technology in place maybe we can make it all the way until the asteroid hits. And by then, we can try to have people spread across a few planets. And then we are good until the sun burns out, or the aliens come for us, or the universe collapses. None of which will be my problem.