Tips for Working with Gas Fermentation: Managing Flammable and Explosive Gas Streams

The first two parts of this series followed gas from its source to the point where microorganisms can use it. 

Part one covered getting a variable, often dirty gas stream ready for the fermenter, while part two covered dissolving that gas into the liquid where the biology happens. 

Gas fermentation relies on flammable feeds like carbon monoxide, hydrogen, and methane, which forces a complete redesign of the plant's engineering and safety systems at commercial scale.

Why Gas Fermentation Carries a Flammability Risk 

Flammable gases require a specific atmospheric concentration range to ignite. Below the lower explosive limit (LEL), the air-fuel mixture lacks sufficient fuel, while above the upper explosive limit (UEL), it lacks oxygen. 

Between those two points sits the window where a spark is enough to start a fire or an explosion.

Keeping a process safe comes down to keeping the gas mixture out of that window, or keeping any source of ignition away from it. Unfortunately, the gases involved in gas fermentation make both strategies a major hurdle.

Hydrogen has an unusually wide flammable range, which leaves very little margin for the mixture to drift before it becomes dangerous. 

Carbon monoxide is flammable across a broad range as well, and it is also toxic, so a leak is both an ignition risk and a health risk.

Methane sits at the center of most natural gas safety work for a reason, and the same limits apply when it shows up as a fermentation substrate. 

Any process using these gases introduces hazards absent in traditional sugar-based fermentation, with the risk scaling directly with the volume of gas moving through the system.

Designing Around the Risk

Managing that hazard is a design problem before it is an operational one. 

The first step is hazardous area classification, a process that identifies potential flammable atmospheric zones surrounding equipment and determines their probability of occurrence.

Those zones then dictate what kind of equipment is allowed to operate inside them, as everyday motors, sensors, or electrical panels that would be fine in an ordinary room can become the ignition source that sets off everything around it.

ATEX-rated equipment and its global counterparts are specifically designed so they cannot ignite the surrounding air.

From there, design introduces active layers of defense engineered to keep the gas out of its explosive limits.

Gas detection placed at likely leak points gives early warning before a concentration climbs toward the danger window. 

Flame arrestors let gas pass through piping while stopping a flame from traveling back up the line. 

Inerting, often by introducing nitrogen, dilutes the oxygen available so that a mixture cannot reach a concentration that will ignite in the first place.

At lab scale, the volumes are small enough that flammability is easier to contain. But moving to commercial scale carries significant risks, as gas volumes climb, leak points multiply, and potential equipment failures carry far greater consequences.

Where This Shows Up in Scale-Up

A design choice that was completely harmless at one liter can become a critical safety issue at ten thousand. 

Gas fermentation often relies on industrial off-gas from steel mills or refineries, where output shifts constantly based on upstream operations. 

A safety design must account for the full range of gas compositions the source will produce over a year of operation.

That’s why flammability controls cannot simply be bolted on once the fermenter is functional. It runs through area classification, equipment selection, and control system design from the earliest stages, alongside the gas handling and mass transfer decisions the first two parts covered.

Addressing safety up front keeps the project scaling forward rather than back to the drawing board.

How We Can Help

Next Rung Technology provides engineering, execution, operations, and consulting services to companies developing sustainable technologies, including a range of fermentation platforms, gas fermentation among them. That work spans early-stage road-mapping and techno-economic assessment through full FEL-1/2/3 design support and skid delivery for pilot, demo, and commercial facilities.

If flammable gas handling, area classification, or the safety design around your fermentation process is the thing standing between you and your next scale-up milestone, reach out through our contact page.

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