Parallel Carbon Wants to Sell Air-Captured CO2 and Green Hydrogen as a Package Deal

Direct air capture has a stubborn economics problem. Pulling CO2 out of thin air is thermodynamically honest work, and every plant in operation today sells its output at prices that only the most motivated corporate buyers will pay. A startup profiled by Chemical and Engineering News this week thinks the fix is not a better filter or a cheaper fan, but a completely different business model: capture the CO2 and manufacture green hydrogen in the same facility, then sell both.

Parallel Carbon, a Jersey City startup launched in 2021, is developing an integrated system that combines direct air capture with water electrolysis. The two products, pure CO2 and green hydrogen, are exactly the ingredients needed to synthesize e-fuels and low-carbon chemicals. Founder and CEO Ryan Anderson told C&EN that producing both together, powered by renewable energy, is what makes the economics work where standalone DAC has struggled.

The economics problem it is trying to solve

Direct air capture sits in an awkward spot. The technology works, the chemistry is well understood, and the buyers exist. But published estimates for first-of-a-kind DAC plants commonly land in the hundreds of dollars per ton of CO2, which is far above the price of conventional carbon feedstocks pulled from fossil sources. The handful of operating commercial plants worldwide have trimmed those numbers but remain expensive.

Most of the industry has responded by chasing cheaper capture: new sorbents, lower regeneration temperatures, waste heat integration. Parallel Carbon is betting that cost reduction alone is the wrong fight. Its argument is that a DAC plant is really an industrial chemistry plant, and industrial chemistry plants are profitable when they sell everything they make. A system that emits nothing and sells two high-value products at once has a different cost curve than one that sells a single credit.

Three chemical steps, one loop

The process, as described in the C&EN profile published October 14, runs in three linked steps. First, ambient air flows naturally through racks of large trays loaded with calcium hydroxide, ordinary slaked lime, which absorbs atmospheric CO2 and converts it into calcium carbonate, better known as limestone. No fans force the air through; it moves on its own, which removes one of the energy costs that burden conventional DAC designs.

Second, the resulting limestone is dissolved in nitric acid. This produces bubbles of pure, ready-to-use CO2, which is the capture product. The third step is water electrolysis, which splits water to generate green hydrogen. The system is designed as a closed loop: the chemicals consumed in capture and acid treatment are regenerated within the process, so the main inputs are air, water, and renewable electricity, and the main outputs are CO2 and hydrogen.

A system that emits nothing and sells two high-value products at once has a different cost curve than one that sells a single carbon credit.

Why hydrogen changes the math

The hydrogen angle is doing most of the economic heavy lifting. Green hydrogen already has established buyers and a global price, unlike CO2, which mostly sells today as a credit or a promise. By co-producing hydrogen, Parallel Carbon turns a carbon-removal plant into a chemicals plant with two revenue streams instead of one.

The combined output is aimed at e-fuels: synthetic fuels made from captured CO2 and green hydrogen that can substitute for petroleum in aviation, shipping, and heavy industry. Those are precisely the sectors, alongside cement and steel, that C&EN identifies as the motivation for DAC in the first place: they cannot be electrified easily, and they will keep burning something. If that something can be manufactured from air and water at a price competitive with fossil fuel, the climate math changes fast. The startup's stated goal is e-fuels that cost less than their fossil equivalents, an ambitious target that would require both cheap renewable electricity and a capture process that shares its costs with hydrogen production.

A closed loop built from industrial chemistry

There is nothing exotic about the individual reactions here, and that is the point. Calcium hydroxide capturing CO2 is textbook chemistry, the same reaction that turns limewater milky in a high-school lab. Nitric acid dissolving limestone is standard mineral processing. Electrolysis of water is one of the oldest industrial processes in existence. The innovation, if it holds, is in the integration: arranging these off-the-shelf reactions so that each step feeds the next and nothing leaves the system except product.

That design choice matters because DAC startups are often judged on the novelty of their sorbents, and novel sorbents carry development risk. Parallel Carbon is instead making a systems bet, using known chemistry in a new arrangement. The tradeoffs are real too. Nitric acid handling at industrial scale is a serious engineering and safety undertaking, and the closed-loop claim will need to be demonstrated at meaningful throughput, not just in a lab.

What to watch next

Parallel Carbon has disclosed $3.6 million in funding from Aramco Ventures, Counteract Partners, the Repsol Foundation, and others, plus additional backing from Tencent's CarbonX Program 2.0, the Chinese tech giant's accelerator for carbon-removal technologies. That is modest money by DAC standards, which tells you the company is still early. The milestones that will matter are the ones every DAC startup faces: a pilot plant that runs continuously, verified numbers on energy consumption per ton of CO2, and evidence that the closed loop actually closes at scale.

The broader signal is worth noting. The DAC industry is splitting into camps: the sorbent optimizers, the energy scavengers hunting for waste heat, and now the product integrators who treat capture as one step in a chemicals business. If Parallel Carbon's approach works, the lesson will be that the cheapest ton of captured CO2 is the one you never had to sell as a ton of captured CO2.