One of the cooler energy projects in development today addresses CO₂, methane, climate change and clean fuels, all at the same time.
That’s “cooler” in the sense of using less heat, as well as being highly innovative in combining natural gas and carbon dioxide to generate fuel.
The gas-to-liquids process is a research project of GTI in metropolitan Chicago, where it’s known as Cool GTL.
Built around a lower-temperature reformer and a high-conversion, low-wax Fischer-Tropsch system, the multistep process currently produces high-quality jet fuel in small demonstration amounts.
GTI hopes to commercialize the project with industry partners, eventually aiming for plant installations around the world.
This is one example of the current direction in energy technology research, where meeting industry needs is being combined with addressing social and environmental concerns.
The Upgraded FT Process
The Fischer-Tropsch process was developed in the 1920s and today is a well understood component of gas-to-liquids technology. Low-temperature FT typically has been known to produce paraffinic, fairly low-quality liquid fuels.
GTI has upgraded the approach in a number of ways, including adding a first-stage, low-temperature reformer, employing two catalysts and suppressing wax production. This novel process was envisioned by Terry Marker, GTI senior institute engineer.
“We’ve always been very interested in renewable gas, and converting that to liquids is a natural extension,” she said.
“The key is, we have a two-step process with two catalysts, and we have two unique catalysts,” Marker added.
Basically, the process feeds CO₂, methane and water through a steam reformer to produce 2/1, H2/CO synthesis gas, then into a FT wax-cracking reactor.
GTI reported a significant benefit of the process is that it not only can convert natural gas and CO₂ to gasoline, diesel and jet fuel, but it also can convert biogas from digestors, CO₂ from ethanol plants and CO₂ recovered by direct air capture.
“All the fuels we use today – there’s enough CO₂ in the atmosphere for that, enough to make all the fuel from the CO₂ in the air,” Marker said.
Low Cost, No Pollution
While CO₂ may be abundant, one consideration is the cost of capturing the CO₂ and making it available for the GTL process, along with the cost of all inputs, because the generated fuel has to be price-competitive with other fuel in the market.
“This has been a step-by-step process and we’ve kept adding innovations. We’ve made three big innovations,” with the compact electric reformer and the dual catalysts, Marker noted.
Using electricity from renewables in the reforming step makes the process even greener, she said, and the system can use 100 percent of its CO₂ input. She contrasted that with ethanol production, where making a pound of ethanol produces almost a pound of CO₂.
“I think most customers want gasoline, jet and diesel, but they don’t want it to be polluting,” Marker observed.
“That’s what’s so neat about this technology – it can do it all,” she added.
Jim Seaba, GTI’s senior director of technology development, said, “As you go forward with this, you can go 100-percent carbon neutral without stranding any assets.”
The Role of Natural Gas
An FT-based process combines hydrogen with carbon monoxide and CO₂ to produce liquid hydrocarbons. The hydrogen can come from methane – natural gas – or electrolysis of water.
“We definitely see natural gas playing a very big role in doing this,” Seaba said.
“With natural gas you can have a lot of CO₂ coming up with that, so there’s no need to strand the resources,” he noted.
Because Cool GTL plants are modular, relatively low cost and small footprint, they can be implemented in a variety of settings, potentially where gas flaring now takes place.
Seaba said the methane-CO₂ process could enable renewable liquid fuels to be produced locally in communities where natural gas infrastructure can be leveraged with waste streams.
“We’re looking for partners – obviously, talking to companies in the oil and gas industry about partnering with us – and we’re looking for partners in other industries, as well,” Seaba said.
“The idea is to put these (fuel plants) out at multiple locations. There’s a lot of opportunity there,” he said.
Logical partners are those that have CO₂ and/or hydrogen sources already in place, but the process is flexible enough to accommodate a variety of company partners, Seaba noted.
“This clean technology really does bridge the gap between today and guiding us to a carbon-neutral energy system where everyone can participate, and the lowest-cost producer wins,” he said.
Through research funded by the U.S. Department of Energy, GTI has completed laboratory-scale testing and is now moving to larger, pilot-scale testing, using biogas as feedstock.
“We’ve scaled it up to a system that’s fairly large here at GTI. It makes a couple of gallons of FT liquids, jet (fuel) and diesel, a day,” Marker said, to meet a DOE goal of producing 100 gallons of renewable jet fuel.
GTI ultimately hopes to commercialize the project, with multiple installations. Seaba said Cool GTL can create carbon-neutral liquid fuels for transportation to address difficult-to-decarbonize applications like aircraft, boats, large trucks and trains.
“Our target size is a relatively small size, a $40 million plant, in that range,” just a fraction of the cost of a full-scale, FT-based fuel operation, Marker noted.
“Within two years we’ll have some customers and be ready to build a demonstration unit,” she said. “In four years, we could be up and running a commercial unit and ready to deploy plants around the world.”