Part IV: Gas fermentation: Scaling a proven technology for climate impact
Credit: Dall-E
Part IV: Gas fermentation: Scaling a proven technology for climate impact
By: Elizabeth Clarke, CTO
Most people think gas fermentation is really, really hard.
What usually comes to mind is low gas solubility and explosion proofing.
Instead the space has dramatically evolved with a new generation of companies successfully commercializing it.
Here’s how C1 fermentation came to be, and why it is a critical climate change technology.
Gas fermentation has been around for millions of years
Plants and algae are nature's original gas fermenters, and methanotrophs - bacteria that use methane to grow - play an integral role in regulating the global methane cycle and reducing atmospheric methane levels.
In the 1970s, companies like Imperial Chemical Industries recognized the value of using these bacteria for protein production. Du Pont and Norferm later scaled up the production of methanotrophs through large-scale gas fermentation at a pioneering gas fermentation plant in Norway; they successfully produced and sold bacterial biomass as fish food. After years of production, a collapse in fishmeal prices and regulatory obstacles in the EU led to its shutdown.
Today, industrial gas fermentation has become a tangible reality with robust, large-scale commodity production. Pioneering companies such as Calysta, Unibio, and LanzaTech have successfully established commercial-scale facilities and products in the market, generating impressive volumes of output.
For instance,
Calysta, in collaboration with Adisseo under the name "Calysseo," currently generates a substantial 20,000 metric tons of protein annually for aquaculture. Looking ahead, they have plans to expand their operations even further, with a facility capable of producing up to 100,000 tons per year on the horizon.
Similarly, Unibio has achieved remarkable success by converting methane into biomass for fishmeal, generating 6,000 tons/year initially. They have recently announced a strategic deal to construct a plant in Qatar, further expanding their production capacity.
Figure: Unibio
LanzaTech, recognized as the world's largest gas fermentation company, went public in 2022 and has rapidly deployed its technology worldwide. Their first gas fermentation plant, operational since May 2018, successfully produces 46,000 metric tons of ethanol per year from syngas (a mixture of carbon monoxide, hydrogen, and carbon dioxide). This ethanol can be used as transportation fuel or transformed into Sustainable Aviation Fuel (SAF). With three plants currently in commercial production, three more scheduled to come online in 2023, and several additional facilities in the engineering phase, LanzaTech's production volume continues to grow at an impressive pace.
LanzaTech's first commercial plant in China - Credit CNN
And they're not alone—companies like Mango Materials, Newlight Technologies, String Bio, and several other startups have proven their technologies and are beginning to scale.
Remarkably, Calysseo, Unibio, and Lanzatech sell commodities (ethanol, single cell protein), which are incredibly sensitive to manufacturing costs. Imagine combining the power of gas fermentation with the product flexibility, genetic tractability, and fast metabolism of “classic” industrial microorganisms such as E. coli and S. cerevisiae to produce higher value chemicals and materials.
What about gas solubility and mass transfer?
This is the most common question we get about gas fermentation. The underlying question is whether we can make product fast enough using gas fermentation.
Traditionally, fermentations have relied on carbohydrates like glucose as the carbon source. These sugars are very soluble in water, allowing for efficient transfer into solution. However, the rate at which the organism can effectively consume the sugar becomes the limiting factor in these systems.
Many fermentations also require oxygen, which is far less soluble than sugars. Engineers have developed various strategies to achieve high oxygen transfer rates, such as employing tall reactors to increase pressure or faster mixing to generate smaller bubbles. These same strategies have been successfully applied to methane and syngas fermentations.
For instance, both Unibio and Norferm have reported biomass productivities of 4 g/L/h (equivalent to at least a 5 g/L/hr methane uptake rate) using their 300kL loop reactor. This level of productivity is comparable to the fastest sugar based fermentations.
Ultimately, it boils down to a tradeoff—adequate mass transfer can be achieved with sufficient energy input, including the energy needed for mixing liquids and pumping/compressing gasses.
From a cost perspective, utilizing low-cost gasses as the feedstock more than compensates for the higher energy requirements.
What about safety?
All commercial facilities require safety controls. Indeed, gas fermentation has safety requirements that are different from sugar fermentation. But the requirements are far below what is standard in petrochemical manufacturing plants which operate at higher temperatures and pressures.
To illustrate, consider the production of acrylic acid from petroleum, which involves combining a flammable hydrocarbon (propylene) and oxygen at temperatures exceeding 300ºC in a highly exothermic reaction. This process is conducted at large scale and high flow rates.
In contrast, a gas fermenter is a tank filled mostly with water at moderate temperatures (e.g. 37ºC). Maintaining the headspace gas outside of explosive limits is a straightforward task and can be accomplished through redundant engineering controls.
Why gas fermentation is key to support climate initiatives and a circular economy
In today's climate crisis, the urgency to address greenhouse gas (GHG) emissions has reached unprecedented levels. We need to rapidly draw down industrial GHG emissions, and to capture gases that we’ve already emitted. We need larger-scale implementation and a wider range of applications. We need new technologies that can economically convert waste into everyday materials, with a focus on high-volume products.
Different solutions will be suitable for different regions, markets, and sources of emissions, and we must deploy them all. Governments must support the development of fermentation infrastructure, including gas-fed bioreactors.
The most effective way to prevent the release of harmful GHGs into the atmosphere is by creating economic incentives that encourage their capture. Gas fermentation, with its ability to transform these gaseous pollutants into valuable products using innovative biocatalysts, is positioned as a vital technology in the circular economy. The successful commercial deployment of large-scale gas fermentation by pioneering companies demonstrates its technical advantages, profitability potential for the industry, and significant impact in reducing emissions.
It is time to explore how we can harness the full potential of gas fermentation to build a more sustainable future.
Loved or hated this post? Tell Elizabeth at hello@imicrobes.com.
About us
Industrial Microbes is developing carbon-negative materials to enable the transition to a circular economy and to reduce the carbon footprint of the chemical industry. We build microorganisms that make chemicals and materials from methane, a greenhouse gas 81x as potent as CO2. Our team has been working to decarbonize chemical production for decades and this series of articles will share our perspective on the massive changes we see coming.