Using gases instead of purified sugars as a feedstock for fermentation can potentially cut operating costs and reduce pressure on arable land. So is gas fermentation the next big thing in biomanufacturing, or does it have limited scope?
While the technology is best-known for making fuel and chemicals (LanzaTech, Phase Biolabs, and Again), it is also being explored by several startups (Circe, Solmeyea, Air Protein, Arkeon, Solar Foods, Aerbio, Unibio) as a platform for food and feed production. LanzaTech is also moving into food and feed, having honed its tech for ethanol and specialty chemical production.
Using gases to feed microbes can lower feedstock expenses, simplify sterilization, allow for longer campaigns, and potentially leverage waste or byproduct gases.
It’s not for the faint-hearted, however. Specialized bioreactors optimized for effective gas-liquid mixing and safety measures for handling gases can add to capital costs and some of the sustainability claims don’t necessarily apply to first generation plants.
But if you can pull it off, gas fermentation offers some distinct advantages, says Dr. Geoff Bryant, CTO at California-based Calysta, which uses methane as the carbon and energy source for its protein-packed Non GMO bacterium.
Prior to joining Calysta, Bryant led Quorn’s R&D and technical teams and spent 20 years with Mars in senior R&D roles.
AgFunderNews (AFN) caught up with Bryant (GB) pictured below at the company’s new industrial-scale gas fermentation facility in Chongqing, China, which is initially targeting the animal feed and petfood markets.
AFN: What makes gas fermentation appealing as a technique for food and feed production?
GB: When I was at Quorn we were looking at ways to improve our capital costs per ton, and Calysta happened to have a pilot plant on the same site in Teesside, in the UK. And as soon as I saw it, I thought, this is the solution!
[To make the unit economics of biomass fermentation work] you need good productivity and long campaign lengths, but as soon as you lose sterility in your fermenter [due to contamination with unwanted microbes, for example], you have to effectively put it down, clean it, turn it around, and it just kills you, it destroys the business model.
But Calysta’s technology basically is almost sterile by design, and I thought this was absolutely fascinating, because methane is the carbon source, not glucose, so any invading bacteria basically can’t eat it.
The [gas] fermentation is also at high temperatures, about 30-40 degrees centigrade, so nothing really grows in it, so it’s almost sterile by design, and inherently infinitely scalable, both on feedstock and on the volume of fermenters.
AFN: What’s the basic process at the plant?
GB: We’ve got a bacterium that feeds on methane and produces a high amount of high-quality protein via biomass fermentation, so you’re essentially growing and harvesting the bug. It’s basically the same as fungal biomass fermentation at Quorn, except we’re harvesting bacteria.
AFN: Tell us about your microbes.
GB: We’ve growing methanotrophs [bacteria that feed on methane] that have been around for billions of years. They’re in your back garden, everywhere, right in the soil, and we’ve got a natural strain [of Methylococcus Capsulatus] isolated from the hot springs of Bath in the UK. It’s not genetically engineered but is an absolute protein machine, about 70% protein.
As for productivity, anywhere north of two kilograms of biomass per cubic meter per hour is seen as a phenomenal output, and we’re nearly at four. What does that mean? In our 400,000-liter fermenters [utilizing a proprietary horizontal ‘U-loop’ design] we’re producing over 1,000kg of protein on a dry basis every hour.
It’s also a continuous process that you can just keep running, although you have to periodically stop things for mechanical reasons if a pump breaks or something like that. From a biological perspective, we aim to run the fermenters for a campaign of about 12 to 15 weeks. But you can basically start it and continuously harvest for months, which again, is a big advantage of our bacterium as it’s so stable.
Some fermentations with fungi have to be stopped after a while because they don’t replicate anymore. In contrast, our bacterium is incredibly stable; it’ll just keep replicating exponentially until you stop it.
AFN: What inputs does your bacterium need to thrive?
GB: Methane is the carbon source, then we also feed it oxygen and ammonia as a nitrogen source. And then we add metal salts that you put in all fermentations. So it’s basically like blowing oxygen, methane and ammonia into some salt water.
We’re using natural gas at the moment [as a methane source] to prove the technology, but ultimately we want to use synthetic methane that can be manufactured from carbon dioxide. So carbon dioxide plus energy and green hydrogen will make a synthetic methane, and ultimately, that’s where we want to go; we want to use 100% renewable feedstocks.
The cost of green hydrogen and renewable energy and the availability of carbon dioxide at scale isn’t there at the moment. But ultimately it will be, and that’s what we’ll migrate to.
The same with ammonia. Right now, we’re using industrial food grade ammonia, but you can obviously move to a renewable source of ammonia as well.
AFN: But isn’t the whole point of gas fermentation to use waste gases for a sustainability/circularity story?
GB: It’s the same challenge facing the carbon dioxide fermentation guys as well. In theory, you can use methane out of the air, or methane out the ground, or carbon dioxide from the air. But the thing is, you just can’t concentrate it. The cost to get it, to concentrate it, and then to push it into your fermenter at the scale you need is prohibitive at the moment.
Now you can obviously get methane from biogas, and you could use that, but that’s the challenge at the moment, to get that local source of available renewable methane in one place at the right cost. But it’s not a huge technical problem, it’s just a question of scale and cost and logistics.
If you look at carbon dioxide, the cost to clean up waste CO2 is very expensive. So the question is, how do you get it?
In that respect we’re in the same boat as everybody else needing a bulk, clean source of CO2, which you can either feed directly into a fermenter, or turn it into synthetic methane and feed that into the fermenter, because it acts as both the carbon source and an energy source. Whereas certainly for aerobic fermentation, if you’re feeding CO2 directly, that serves as a carbon source, but not an energy source. You’ve then got to feed hydrogen into the fermenter, and where you’ve got hydrogen, oxygen and CO2, you’ve got safety issues you have to control.
So we like methane as we think it’s easier to manage and nothing else eats it. What we need to do is find that long term solution for producing synthetic methane. But in the meantime, we can just use natural gas. And the carbon emissions from this are still orders of magnitude below those from animal agriculture.
From a water and land use perspective, meanwhile, we’re basically water neutral, and our tech can produce 100,000 tons per year on 10 hectares of developed land vs a quarter of a million hectares of arable land for an equivalent amount of soy protein.
AFN: What’s the downstream process?
GB: For aquaculture and for pet food, it’s a crude protein; we essentially just harvest the biomass. It’s about 2% solids in the fermenter, so we centrifuge it to about 12 to 15% so it’s about the same concentration as milk, and then we evaporate it and spray dry it.
AFN: What markets are you targeting?
GB: The plant was built in China as a joint development between us and [animal nutrition co] Adisseo to service the Chinese aquaculture market, which is massive, and we’ve been serving that market since the start of 2024.
Because we see our next plant as being totally dedicated to pet food in developed markets such as Europe and the US, we’ve got a certain allocation of product from the factory to go to Europe to prove there’s a market in pet food and justify building the next factory.
But we started with aquaculture and we have the approvals, we have the scale, we’ve proven the technology, and we’ve got the right cost structure as firms are looking for alternatives to fishmeal and aquaculture volumes are only going to go up.
Aquaculture companies have started to replace some fishmeal with soy protein, but it isn’t suitable for animals such as salmon and shrimp. We’re also finding that some pet food customers find that the palatability isn’t very good for insect protein, plus the cost and availability still isn’t there.
FeedKind [the brand name for Calysta’s microbial protein] has an amino-acid profile which makes it particularly attractive for finfish and shrimp, and we’ve also got studies showing it can improve gut and immune health in shrimp.
On petfood, which we see as our biggest opportunity, we’ve done a lot of feeding tests and it’s equal to the best quality animal meal. It took us a while to get the manufacturing and export licenses, but we had our first big shipment to the European pet food market last August.
On the human food side, we are still building our safety dossier, and we know it’s a lengthy process to get approvals, but we see this as a bulk protein that could go into high-carbohydrate, low-protein products such as breads and pasta. It provides fantastic protein and micronutrients such as Vitamin B12 that you miss out on if you take meat out of your diet.
It also has lots of heme in it, naturally, so that’s something in the future that we can look at.
AFN: How do investors regard what Calysta is doing?
GB: We are in the process of our next raise, which will have to be several hundred million dollars because we’ll be building a plant which would be tens of thousands of tons of output.
But the good news is, because we can show the performance of the China plant, which has two fermenters, each with a capacity of 10,000 tons a year, it’s easier now for future investors to get behind us, because they can go and visit our site, see the data, and see the product.
Further reading:
Read the orginal article: https://agfundernews.com/can-gas-fermentation-deliver-on-its-green-promise-for-food-and-feed-in-conversation-with-calysta
