Carbon dioxide. Black = carbon, red = oxygen
I came across an article about making liquid fuel from carbon dioxide. A Google search quickly turned up three methods, two currently ready for commercial development.
They all take carbon dioxide from the atmosphere and make various fuels with it. Burning it returns carbon to the atmosphere, of course, but it came from the atmosphere in the first place, not from the ground. So they’re carbon neutral.
Maybe someday you’ll find gasoline from captured carbon dioxide at the pump when you pull into a gas station. The barriers are more economic than technological.
Carbon Engineering
Coal-fired electric plant pumping out carbon dioxide
The world pumps about 40 billion tons of carbon dioxide into the atmosphere every year. It would make sense to suck it back out.
Standard technology uses giant fans to put air into contact with a solution that separates and traps carbon dioxide. Heating this solution, along with other commonplace chemical procedures, extracts and purifies the carbon dioxide. Various sequestration strategies exist for storing it. Or manufacturing processes can use it as a raw material for hydrocarbons.
This process makes environmental sense, but not yet economic sense. Theoretical analyses estimate the cost at as much as $1,000 per ton.
A Canadian company, Carbon Engineering, has worked out a way to reduce the cost to $100 per ton. Even at that price, it couldn’t find buyers, so it decided to use it to make a liquid fuel.
Using hydropower for electricity, the process extracts hydrogen from water by electrolysis. Combining the captured carbon dioxide, the process makes a fuel that can be blended with gasoline, diesel, or jet fuel. Or used by itself in place of those fuels. Existing infrastructure for fuel distribution and transportation can easily handle it.
The process costs more than starting with a barrel of oil right now. The economics would change if any government started to put a price on carbon emissions.
With the trend toward electric vehicles, this kind of fuel will work most successfully with the kinds of heavy transportation that are difficult to electrify, such as shipping.
Dimensional Energy
Scientists at Cornell University have devised a somewhat different system of making liquid fuel from carbon dioxide. A startup, Dimensional Energy, aims to commercialize it.
Rather than taking carbon dioxide from the atmosphere, it captures it from factories before it gets there. Its reactor adds water and sunlight to mimic the process of photosynthesis and produce synthetic gas or methanol.
Reactors can be built at the factory to eliminate the need to transport the carbon dioxide. The resulting fuel is useful for cooking, heating, and any other energy application that can use similar fuels now on the market.
Again, the carbon dioxide released by burning it came from captured carbon dioxide in the first place. So it doesn’t add to the net amount of carbon in the atmosphere.
Rice University
Engineers at Rice University have found an inexpensive way to turn captured carbon dioxide into formic acid, the compound that creates the sting from ant bites and bee stings. So far, it appears they haven’t formed a startup to market the process.
Existing commercial processes for making formic acid from carbon dioxide require catalysts from transition metals, such as highly toxic cobalt or cadmium. They use a salt-water electrolyte. Current technology can only make these catalysts on a scale of grams or milligrams. The formic acid bonds with the electrolyte, requiring and extra step to remove it.
The Rice engineers made two critical changes to this process. First, they used bismuth for a catalyst. It’s more stable than other metals, so it doesn’t degrade as fast. It’s also far less toxic than other heavy metals. And it’s possible to make catalysts on the scale of kilograms.
Second, they used a solid electrolyte. The formic acid doesn’t bond with it, so it emerges from the process much more highly concentrated.
Industry has many uses for formic acid. Among others, it can be used in fuel cells instead of pure hydrogen.
The difficulty in compressing hydrogen gas contributes to the problems of making cars run on hydrogen fuel cells. Formic acid holds about a thousand times as much energy as the same volume of hydrogen. Whatever carbon dioxide it emits can be immediately captured to produce more formic acid.
Carbon dioxide is essential for life, but enough is enough. We are approaching catastrophic levels in the atmosphere. But like all environmental problems, if we can find a way to view it as a resource instead of a waste, we can get it under control. Making liquid fuel from carbon dioxide makes sense.
Sources:
Engineers build a device that effectively transforms CO2 into liquid fuel / Mike McRae, Science Alert. September 9, 2019
Here’s a machine that turns carbon dioxide into liquid fuel / Jennifer Leman, Popular Mechanics. September 4, 2019
How to suck carbon dioxide from the sky for fuels and more / Phys.org. June 7, 2018
Rice reactor turns greenhouse gas into pure liquid fuel / Mike Williams, Rice University press release. September 3, 2019.
Shine on: Dimensional Energy turning carbon dioxide into fuel / Jeff Kart, Forbes. August 20, 2018
This gasoline is made of carbon sucked from the air / Stephen Leahy, National Geographic. June 7, 2018
Image credits:
Carbon dioxide model. Public domain from Wikimedia Commons
Coal plant. Some rights reserved by lowjumpingfrog (link no longer works as of August 2017)
Sunshine. Some rights reserved by armaggesin.
Ants. Public domain from Wikimedia Commons rel=”nofollow” https://commons.wikimedia.org/wiki/File:Ants_on_candy.jpg
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