Closed Loop Outgassed Materials

Monitor outgassed materials in bioreactor headspace for closed-loop system control

Measuring outgassed material in the bioreactor headspace is a powerful tool for understanding the metabolic activity of your cell culture and the effectiveness of your bioreactor setup. While it is more resource intensive than simply measuring dissolved oxygen and pH, outgassing measurements ensure that your culture is healthy, that you can maximize your yields, and that you can effectively scale the reaction.

Healthy CO2 levels mean healthy cells

Bioreactor systems are designed so that carbon dioxide, the metabolic byproduct of cell growth, will rise into the headspace of the reactor, where it is then removed by the overlay airflow sweeping the system. Measuring the CO2 levels removed from the system can provide invaluable information about both the metabolic rate of the culture and the overall health of the system.

Low levels of CO2 in the headspace likely indicate that the culture is growing slower than expected. This may indicate non‑optimal system design, system flaws, or improperly calculated scale‑up parameters. All of these have the potential to drastically and detrimentally affect the development timeline.

These low CO2 levels in the headspace may also be a sign that CO2 is remaining trapped in the medium. If the levels of CO2 in the medium get too high, the steep concentration gradient will prevent any further release of toxic CO2 from the cells. This buildup is often a result of foam accumulating at the top of the culture medium due to agitation and sparging. If noticed, it can be countered by adding anti‑foaming agents.

Trapped CO2 within the culture medium poses additional danger to the cell environment, as it will react with water and create carbonic acid. This lowers the pH of the system and the highly acidic environment, in combination with the cells’ inability to release toxic material, is likely to kill the culture.

Given that pH has a profound impact on cell health, and can drastically fluctuate with changing CO2 levels, pH probes have long been standard in bioreactors. Combining this tool with outgassing measurements enables thorough diagnosis and correction of any issues that arise in a cell culture.

Measure oxygen transfer using the respiratory quotient

Oxygen mass transfer is most often calculated using dissolved oxygen and pH measurements. However, recent research shows that it is preferable to calculate this parameter using the respiratory quotient, the ratio of oxygen consumed to carbon dioxide produced during a phase of culture growth.

The respiratory quotient is a key parameter for controlled scale‑up of a bioprocess. It uses measurements of headspace gas levels to provide real‑time information on the metabolic growth rate of the culture. That data can then be fed into a growth model for planning purposes, or into the controller of a reactor system, for tight, closed‑loop control of the system.

Monitor and control growth processes in real-time

Photo of a gauge for measuring CO2

Gauge for measuring CO2

It can also be useful to measure the headspace levels of gases other than CO2. These measurements can be used to calculate oxygen limitations and oxygen transfer rate, predict biomass concentrations, and otherwise monitor and control culture growth.

Consider oxygen transfer rate (OTR) — information gained from monitoring headspace levels of oxygen. Maximizing OTR is necessary to maximize process yield, and we know that any oxygen in the headspace has not been taken up by the cells. So monitoring oxygen levels in the headspace can let us know if cells aren’t taking up expected oxygen levels. Because OTR is highly dependent on the design features of the bioreactor (shape, bubble size, impeller type, sparger type, etc.), this indicates the reactor is not optimally designed.

Analyzing unknown mixtures of outgassed materials in the headspace can also provide information about your process and product purity. The headspace mixture can be flowed into a mass spectrometer to identify the components. This can ensure that there are no impurities and that the culture is behaving as expected.

Overall, these measurements serve to accurately control batch‑fed processes in real‑time. Monitoring the outgassed material in the bioreactor headspace and linking that data back to the system controller provides real-time analytics for controlling the bioreactor system. This then works to ensure high batch quality at any phase of biologics development.

Enabling Liquid Hydrogen Fuel Systems in Maritime Innovation

Alicat MCRQ Mass Flow Controllers Support TU Delft Hydro Motion Team’s Hydrogen Boat for the Monaco Energy Boat Challenge

Feb 20, 2025 | Bioreactors & Fermenters

Empowering Discovery on Water

The transition to sustainable energy in the maritime sector demands more than ambition, it requires precision. That is why Alicat Scientific is proud to support the TU Delft Hydro Motion Team as a Bronze Partner in their groundbreaking 2025 campaign: to design, build, test and race Mira, a liquid hydrogen-powered boat at the Monaco Energy Boat Challenge.

Equipping this innovative project with our MCRQ mass flow controllers enables the team to manage hydrogen fuel delivery safely and accurately, helping them prove that liquid hydrogen can power the next generation of clean marine propulsion.

Mira at the official reveal, Hydro Motion Team’s 2025 liquid hydrogen-powered boat.

Figure 1: Mira at the official reveal. Hydro Motion Team’s 2025 liquid hydrogen-powered boat.

The Challenge: Making Hydrogen Work for Maritime Transport

The goal of the TU Delft Hydro Motion Team is as ambitious as it is inspiring: to design, build, test, and race a fully functioning boat powered by liquid hydrogen, all within one year, and to compete at the Monaco Energy Boat Challenge 2025. But beyond the competition itself, the team’s mission reaches further. By proving that a boat can operate successfully on liquid hydrogen, they aim to spark broader innovation across the maritime sector and demonstrate hydrogen’s potential as a clean, scalable alternative to fossil fuels.

This project builds on the team’s past successes with compressed hydrogen, already a proven, zero-emission marine fuel. But as the team pushes for longer range and greater onboard efficiency, storage volume and energy density become the next major challenges. To solve this, the team chose to work with liquid hydrogen. With a volumetric energy density three times higher than compressed hydrogen at 350 bar, liquid hydrogen offers a powerful solution for saving space and extending endurance, key requirements in performance vessels.

But storing and using liquid hydrogen introduces challenges. The fuel must be kept at -253°C, requiring insulated cryogenic tanks. The team addresses this with a custom double-walled, vacuum-insulated carbon-fibber tank system, limiting heat ingress to just 7 watts, equivalent to a small LED bulb. To avoid wasting energy, waste heat from the fuel cell is used to bring hydrogen up to the required ~20°C operating temperature before reaching the fuel cell.

These trade-offs (boil-off rates, tank volume, storage weight, and onboard vaporization) are exactly the kinds of real-world constraints this project is designed to explore. And while Mira is a compact, foiling boat, the broader engineering question remains: could a system like this scale to larger vessels, such as ferries? That is the kind of thinking Alicat is excited to support with partners who are pushing the boundaries of what is possible.

The Role of Alicat: Flow Control After Vaporization

In Mira’s hydrogen system, hydrogen is stored as a cryogenic liquid. Before reaching the fuel cell, it passes through a vaporizer, transitioning into gas at ambient temperature. This phase is critical: delivering gas at the right pressure and flow requires stable regulation, fast feedback, and precise control.

Simplified diagram of the Hydro Motion Team’s hydrogen system.

Figure 2: Simplified diagram of the Hydro Motion Team’s hydrogen system.

To meet this need, the team integrated the Alicat MCRQ mass flow controller immediately downstream of the vaporizer. This device manages the mass flow of hydrogen gas into the fuel cell and enables:

  • Delivers stable and precise feed pressure to the fuel cell.
  • Measures hydrogen consumption through real-time mass flow monitoring
  • Monitors pressure and temperature to help prevent fuel cell issues like dehydration or fuel starvation.
  • Supports test validation and real-world performance optimization.

Compact, ATEX Zone 2 certified, and designed for fast system response, the MCRQ integrates easily into the tight constraints of a race-ready vessel. Its role is vital during system development, helping the team collect data, tune parameters, and prepare for race-day performance. In short, it helps translate bold hydrogen engineering into operational reliability.

Alicat’s MCRQ unit mounted inside the Hydro Motion Team’s hydrogen control system.

Figure 3:  Alicat’s MCRQ unit mounted inside the Hydro Motion Team’s hydrogen control system.

Why the MCRQ Was Selected

The Hydro Motion Team, together with our application engineers, selected the Alicat MCRQ series for its proven capability in low-flow hydrogen gas applications, offering a powerful combination of precision, speed, and safety. Key features that influenced the decision include:

  • Flow range of 0–1.5 g/s, which translates to ±0.01 g/s uncertainty at a nominal 1 g/s flow, small enough to maintain consistent fuel cell output.
  • 4–20 mA analog output, chosen specifically for its high-speed update rates (kHz range)
  • ATEX Zone 2 IIC certification, requiring minimal additional safety infrastructure.
  • Upstream valve position, enabling precise regulation of downstream feed pressure, supporting target values like the ~2.5 bar commonly seen in fuel cell stacks.
  • ±1.0% accuracy of reading (or ±0.2% of full scale)

Together, these features provide the team with a robust, compact, and responsive solution, a key enabler of real-world testing and a step toward scalable, clean hydrogen propulsion.

Competition Progress and What Comes Next

The TU Delft team unveiled the boat, Mira, earlier this year and is now deep into the testing phase, preparing for the Monaco Energy Boat Challenge 2025.

As testing progresses, the team continues optimizing the integration between hydrogen storage, vaporization, and control systems. Alicat’s instrumentation plays a central role in capturing this performance data for analysis and refinement.

This partnership represents more than a technical contribution. It reflects our belief that sustainable innovation thrives where education, engineering, and real-world experimentation meet.

By supporting the Hydro Motion Team and their work on Mira, Alicat contributes to:

  • Advancing liquid hydrogen fuel systems in marine transport
  • Empowering hands-on engineering education
  • Promoting practical low-emission propulsion technologies

We are honoured to be part of this project and proud to know that our instruments are helping to steer the future of clean maritime energy.

Together, we are not just measuring hydrogen. We are helping to Fuel the Future.

Your Title Goes Here

Alicat Newsletter

Sign-up for our newsletter to be informed of product applications, updates, news, and upcoming events

Related articles

Pharmacy Optimization Tools

Only 12% of drugs that make it from the lab and into phase 1 clinical trials end up receiving FDA approval. However, planning for eventual pharma scale‑up long before...

read more