It took just four phone calls to leave his position as a venture capitalist.

The first came from Marble, a Paris-based startup studio, who had a scientist seeking help in founding a company that would remove carbon dioxide directly from the atmosphere – known as direct air capture, or DAC in experts' lingo.

"They approached the subject as being a DAC company, and I was like, 'No way. No way. I am not going in that space,'" Fiedorow said to TechCrunch. "I did not want to invest in a DAC."

But he kept an open mind and met with the scientist, Steven Bardey. He was "all in" after a few meetings with his co-founder, he said: "Once we dug into the numbers, once we did a back-of-the-napkin techno-economic assessment, that was the switching point for me.".

Fiedorow and Bardey started Aerleum in 2023 to improve the DAC technology that Bardey had been developing. Most DAC companies focus on the capture part of the process, essentially building really big sponges that can absorb carbon dioxide from the air. It's not easy or cheap: at today's enhanced levels, CO2 is just 0.04% of the air we breathe.

Once captured, most DAC startups then need to identify a user of that carbon dioxide. They can compress it and sell it to oil companies that force it into reservoirs in an effort to squeeze out more oil, thereby weakening it as a viable solution for climate change. Or they can sell it to a sequestration startup, which simply injects it deep into the Earth for storage. Yet other firms would sell it to chemical companies that take it to their plant and bust it up into other chemicals.

"Should we really have to go through all of those steps, or can we just circumvent some of them?" asked Fiedorow as he and Bardey thought through their process. "Where do you have the most energy penalties? It was really in the middle, the intermediate steps where you have to dissolve the CO2, compress it, and transport it."

To get rid of that extra step, Aerleum has developed a material that captures carbon dioxide in two steps and converts it into another compound. Methanol, an alcohol that can be burned as a fuel source in cargo ships or used as an ingredient in making other chemicals, including aviation fuel, is the startup's first target. The proprietary material is sponge-like, Fiedorow said, and inside the pores, a catalyst helps facilitate chemical reactions being pursued by Aerleum.

Capture carbon dioxide: Aerleum puts the material in a form of a box that allows air to pass through it. Once saturated with carbon dioxide, technology closes the box and puts hydrogen gas in. The hydrogen reacts with the carbon dioxide to form gaseous methanol. Methanol is then pumped from the box and purified.

For now, the intention with Aerleum is to make use of the existing carbon in the air. Fiedorow said the company has conducted experiments with carbon dioxide levels as high as 15%, so it's possible the material could be used to capture the gas from some industrial processes.

Having raised seed funding worth $6 million from 360 Capital and HTGF, in addition to the participation of Bpifrance, Marble, and Norrsken, Aerleum is currently going to build a pilot of its DAC device.

The company hopes within the near term to be able to produce methanol using its process for less than $1,200 per metric ton. Methanol now costs buyers anywhere from about $380 to $780 per metric ton depending on where they're located.

In five years, that is the aim: cut almost in half to $650 per metric ton. "That's where we start to be super competitive, even with fossil fuels," he said.