The Prometheus Plan: Making Synthetic Fuel An Affordable Reality

It’s not an exaggeration to say that we live in interesting times. For enthusiasts of internal combustion (IC), the world is changing way too fast and the push from the environmental side to eliminate internal combustion engines is gaining momentum. Our friends inside GM tell us the company has stopped funding research on internal combustion and Nissan has made it official with its plan to stop the same for all vehicles except those intended for the U.S. market. This is not good news.

But all is not lost. The big issue is that internal combustion engines produce, among other pollutants, a large amount of carbon dioxide (CO2). This byproduct is what has all the environmentalists concerned with what is commonly referred to as the greenhouse effect. According to these prognosticators, CO2 is the main cause of the increase in our planet’s temperature.

Beyond this discussion, what if there was a way to pull CO2 out of the air and, through some catalytic wizardry, and use it to create a synthetic fuel? If that sounds a bit like a Buzz Lightyear fantasy, we’re here to tell you, it’s not quite as comical as it sounds.

Prometheus Fuels is the company behind the process and its goal, as we will explain, is to pull carbon from the air and combine it with hydrogen from water. Then, through a complex set of catalytic processes, recombine these elements into synthetic fuel. If the name Prometheus sounds familiar, you might remember him as the god of fire from Greek mythology. But, the Prometheus idea is no myth.

Tital Fuel Forge synthetic fuel

This Prometheus illustration reveals a Titan Fuel Forge that is the overall process designed as a single source fuel-production plant. It pulls CO2 out of the air in the carbon salvage process, Step.1 In Step 2 renewable electricity turns the CO2 and H2O into long-chain alcohols which are sent to a fuel extraction chamber where remaining water is removed (Step 3). The final step uses a catalyst to convert the alcohols into fuel in Step 4.

Back To Chemistry Class

Unfortunately, the description of this rather complex process does require some knowledge of chemistry. If you are like us, this was not our favorite class in school. So, bear with us as we attempt to describe this fascinating approach to produce fuel from air and water.

First, as always, we must cover some basic chemical terms and processes. Our atmosphere contains approximately 78-percent nitrogen and 21-percent oxygen, with a few other trace elements tossed in to complete the picture. Water of course is hydrogen and oxygen combined into a molecule of H2O with a strong electron (covalent) bond. Gasoline consists of just carbon and hydrogen atoms linked together to create what is called a hydrocarbon chain. Current gasoline is also mixed with ethanol, which also adds a slight amount of oxygen.

Traditional gasoline is refined from oil that is pulled from the ground. But there are other ways to make gasoline. The Germans produced gasoline during World War II by synthesizing it from coal or natural gas. Coal contains the requisite carbon, hydrogen, oxygen, nitrogen, and sulfur. While these processes worked, they were not energy- or emissions-efficient.

carbon salvage synthetic fuel

This is a more detailed illustration of the carbon salvage portion. Large fans blow air across water pulled from the atmosphere toward a mesh grid that absorbs H2O and CO2.

The Prometheus plan begins with what the company calls a Titan Fuel Forge. This is a self-contained unit that can be built to fit inside a 40-foot shipping container. This unit is intended to be easily shipped to any location where there is a ready supply of electrical (solar, wind, etc.) power. The company’s MetaForge factory idea is to mass-produce these Titan Fuel Forges and ship them anywhere around the world where they can produce fuel with only inputs of renewable energy, water, and air.

Prometheus begins this process by extracting carbon dioxide from the air and combining it with H2O pulled from existing water vapor in the air, through a catalytic process, to produce alcohols like ethanol. We know this as “white lightning” or “sippin’ whisky” but also propanol and butanol, which can be used as fuel. These become the starting point for synthetic gasoline.

In the Prometheus process, this alcohol is further catalyzed to produce more complex hydrocarbon chains that can be reconstructed into gasoline, diesel fuel, or jet fuel. While jet fuel sounds exotic, it can be accurately described as a more highly refined form of kerosene.

faraday reactor synthetic fuel

In the electrical charging portion, the grid operates somewhat like an automotive 12-volt battery with anode and cathode plates. In the Faraday Reactor, the carbon molecules are energized and combined with hydrogen from water to form long-chain alcohols including hexanol, ethanol, propanol, and butanol.

The Prometheus Process

Our description of the Prometheus process is extremely generic in order to save us from what otherwise might tumble into a complex maze of chemical formulas. The Prometheus website goes into more detail about the process and it is worth the time to investigate should you desire to know more. One important key to the entire process is the energy required to first separate and then recombine these various chemistries to create the hydrocarbon compound.

Let’s dive a little bit deeper into the process. The Direct Air Capture system pulls CO2 out of the atmosphere, requiring 500 pounds of air to capture a single pound of CO2. Next, the CO2 is applied to an electrochemical stack called a Faraday Reactor. In this process, renewable electricity charges the carbon with hydrogen molecules from the water to create long-chain alcohols. A byproduct of this process is oxygen, which is released into the atmosphere. According to Prometheus, the oxygen from one Titan Forge would produce oxygen levels equivalent to 2.5 square miles of forest.

molecular sorting synthetic fuel

In Stage 3, the water and alcohol are processed through a single filter tube membrane called a Maxwell Core that separates the water from the alcohol. This is a new type of membrane specific only to Prometheus, which eliminates the need for expensive and energy-intensive traditional distillation.

The application of electrical power is a critical component of this process since it is the major factor related to the cost of the synthesis process. This reliance on green energy contributes to making a zero-net carbon fuel. The Prometheus plan uses the combination of solar, wind, hydro-electricity, and even nuclear sources to supply the electrical power necessary to complete the synthetic process.

In years past, when fuel prices have soared, the hucksters come out of the woodwork, attempting to sell conversion kits that separate hydrogen from water and then combust the hydrogen in internal combustion engines. [Ed. Note: The charlatans Jeff is referring to are the “run your car on water” people, not the actual hydrogen-powered internal-combustion researchers.] This process isn’t very successful because hydrogen requires special handling and tuning in order to make power. The Prometheus system is far more sophisticated and while extracting hydrogen from water does occur, it goes a step further to recombine the hydrogen with carbon to create a liquid fuel that is atomically identical to fossil-based gasoline.

alcohol catalyst synthetic fuel

In the fourth Titan Fuel Forge step, a catalyst is used to remove the remaining oxygen and lengthen the hydrocarbon chains with hydrogen to produce the various types of fuels including diesel fuel, jet fuel, and gasoline.

Prometheus is careful to emphasize that its synthetic gasoline is not a zero-emission fuel. When any gasoline is oxidized, the resulting emissions include hydrocarbons in the form of unburned fuel (HC), carbon monoxide (CO), carbon dioxide (CO2) and oxides of nitrogen (NOx). The Prometheus approach emphasizes a zero-carbon-gain solution. In this case, the carbon is pulled out of the atmosphere, combined with hydrogen and oxidized through combustion, and finally re-introduced into the atmosphere as a component of exhaust emissions. This theoretically produces a zero carbon-gain situation. Plus, Prometheus fuel does not include sulfur and a few other nasty impurities that are currently present in fossil gasoline.

On the left is a representation of the octane hydrocarbon chain with the formula C8H18. On the right is the ethanol molecule C2H6O with two carbon, six hydrogen, and one oxygen atom. That one oxygen atom is what makes ethanol an oxygenating compound in fuel.

Purity Of The Soul

Another advantage of this synthetic fuel is its purity. Current fossil-fuel gasoline contains much more than just hydrocarbons. Among the additives in gasoline are ethers commonly known as aromatics that are extremely hazardous to human health. Generally, these are known by their acronym BTEX which stands for benzene, toluene, ethylbenzene, and xylene. When combusted, BTEX forms ultra-fine particles, aptly called UFPs, that can directly enter the bloodstream through the lungs and are highly carcinogenic. Synthetic fuel contains zero BTEX aromatics.

Critics of synthetic gasoline maintain the production of this fuel is not energy efficient. A story published in Green Car Reports contends that a gallon of gasoline can produce the equivalent of 32 kilowatt hours (kWh) of electrical power. The story contends that a gallon of synthetic fuel will require twice that amount – or 64 kWh of energy to produce. However, the story did not establish how they obtained that number.

Prometheus RAECR synthetic fuel

In this graphic, Prometheus Fuels explains the process as a version of the combustion cycle they call RAECR (pronounced “racer”) that stands for Recharging & Atomic-sorting Electrochemical Combustion Reversal.

Comparing that energy requirement to the mileage potential of an electric vehicle like a Tesla, the Green Car story contends the electric car would be 10 times more efficient from a mileage standpoint. In other words, an electric car could run 10 times further than the equivalent energy applied into an internal combustion engine. This may or may not be accurate and ignores the reality of retaining internal combustion engines as useful transportation, especially considering the total number of internal combustion vehicles in the world today. [Ed. Note: It also ignores the fuel portability and storage issues that electric vehicles currently face.]

The future for synthetic fuels looks rather promising. The key appears to be how easy it will be for Prometheus to manage the energy cost of producing the fuel versus the current cost of traditional fossil fuel. If the Prometheus price is slightly above the local price of gasoline, this would make synthetic fuel more attractive for performance enthusiasts, especially if there is an octane benefit.

synthetic fuel

One part of this synthetic fuel process that we did not cover is the fuel’s octane rating. This would be a big part of the attraction of a synthetic fuel if it can achieve an AKI (octane rating) higher than 91 to 93, to feed a high-performance engine like this supercharged LS engine.

Article Sources

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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