I admit that writing about this month’s topic makes me really feel a bit like Charlie Brown working towards Lucy and her soccer. This specific soccer, as a common idea, is simply so alluring: Take an issue (extreme atmospheric CO2) and switch it straight into an answer that lets us maintain driving the autos we love—by way of carbon-neutral gasoline, diesel, and jet gas. This newest scheme solves lots of the issues which have yanked the ball on my earlier runs, giving me the braveness to barrel towards it yet one more time.
My three prior columns explaining methods of changing atmospheric CO2 into liquid fuels ran in July 2008, June 2012, and Oct 2018. The early concepts began by scrubbing CO2 from the air with an absorbent compound similar to sodium hydroxide in water, isolating the CO2, cracking it into carbon monoxide, after which hydrogenating it by way of varied catalytic reactions similar to Fischer-Tropsch. Capital and power enter prices doomed these concepts.
Ionic salts and formic-acid gas cells working in reverse helped deliver the projected power enter value all the way down to round $5-$8/gallon once I wrote my second column. Then Carbon Engineering (with backing from Invoice Gates) leveraged pulp/paper mill tech to drop the CO2-scrubbing value to in regards to the worth established for carbon-offset credit by the California Low Carbon Gas Commonplace. Mixed with anticipated drops in the price of the proton-exchange membranes that had been to offer the clear hydrogen, Carbon Engineering reckoned the per-gallon gas worth would fall to inside 50 % of upper 2018 pump costs.
Now Prometheus Fuels is aiming three new silver bullets at this drawback:
- Aqueous CO2 electrolysis utilizing base-metal catalysts to show CO2 straight into ethanol;
- Separating the ethanol from the water with out an energy-intensive distilling course of; and
- Upgrading the ethanol to gasoline, diesel, or jet fuels utilizing exothermic catalytic reactions, which give off warmth relatively than absorbing it.
The CO2 assortment step nonetheless requires a big air-to-water contact space like a cooling tower. However relatively than attempting to chemically isolate pure CO2, the electrolysis step can occur with simply 2 % CO2 in water.
The electrolysis step employs sheets of graphene lined in carbon nanospikes doped with copper nanoparticles. This anode’s intense folds and spikes assist scale back the CO2 to CO after which seize hydrogen from the water to kind ethanol at a 63 % Faradaic effectivity (the variety of electrons that find yourself within the ethanol) with 84 % of the CO2 changing into ethanol.
Ethanol then will get separated from the water by way of carbon nanotube membranes which can be extremely selective for alcohols whereas rejecting water (I’ve mates like that). Minimal power is consumed on this step.
Upgrading from ethanol to advanced hydrocarbons includes novel however cheap zeolite catalysts involving indium and vanadium (InV-ZSM-5). The response takes place at atmospheric stress with out added hydrogen, and the method can tolerate water within the consumption stream. It happens at elevated temperature, however the general web response produces its personal warmth.
The ensuing CO2-based crude inventory accommodates no sulfur, benzene, heavy metals, or different impurities that petrochemical refiners should cope with. A 3rd of the ensuing liquid hydrocarbon combine contains chains of 5 carbons or extra, and the calculated analysis and motor octane numbers are 105.7 and 90.6, respectively. Your entire course of will be operated with (clear) electrical enter solely and will be turned on and off rapidly to match intermittent renewable power provides.
Los Angeles simply contracted a long-term buy of photo voltaic power at 1.997 cents/kWh. Presuming 60 % electrochemical effectivity, the 36.three kWh of power in a gallon of Prometheus gasoline might require 61 kWh of enter power, or $1.22 price of sunshine. This worth would not embrace the CO2 scrubbing or remaining refining and different prices, however neither does it presume carbon offset credit which will apply.
Water utilization within the CO2 scrubbing may very well be the place Lucy yanks my soccer once more, however BMW i Ventures simply invested $12.5 million in June, and Prometheus has introduced plans to start out promoting its gasoline in California on the finish of 2020. Would possibly I lastly make contact with my soccer and cut up the uprights?