Single-cell protein (SCP) was expected to become one of the feed industry's biggest sustainability breakthroughs, offering a new protein source while reducing pressure on traditional ingredients. Yet years after the first wave of enthusiasm, commercial adoption remains limited. Despite strong potential in aquaculture, high production costs, uncertain supply and cautious buyers continue to slow SCP's journey from innovation to mainstream feed ingredient.
The history of SCP protein is a story of failed promises and tremendous disappointments. One of the first attempts to bring it to the market was undertaken by Birmingham, England-based firm ICI's Pruteen. In the late 1970s, the company developed Pruteen, a microbial protein made by growing bacteria on methanol. At first, it was expected to be a major success; research found that up to 80% of fishmeal could be replaced in rainbow trout diets without adverse effects.
But the economics killed it. ICI's Pruteen production was eventually abandoned because production costs were high while competing soybean meal prices were falling.
The Soviet Union offers an even darker chapter in the SCP history. In the 1970s, Moscow embarked on an ambitious program to turn hydrocarbons into animal feed, eventually building 12 plants with combined planned capacity approaching 1 million tons per year of yeast-based protein Paprin. But the experiment that was expected to revolutionize the feed industry proved to be a disastrous experiment.
Single cell proteinsCourtesy Unibio
Animals fed the protein reportedly developed fertility problems, disturbed pregnancies, deformities and severe metabolic disorders, while later research linked the product to abnormal amino acids accumulating in nerve-cell membranes.
In the modern era, technologies have improved, but SCP projects still fail to meet expectations.
In 2017, Calysta and Cargill broke ground on NouriTech, a 37-acre facility in Memphis billed as the world's largest gas-fermentation operation to produce FeedKind SCP. The plans were ambitious: the plant was supposed to produce about 200,000 tons of FeedKind annually at full capacity.
But this project did not become the commercial-scale facility that was promised. Instead, Calysta and Adisseo subsequently pursued a different project in Chongqing, China. That facility was announced in 2020 with a first phase of only 20,000 tons per year, with a later expansion to 100,000 tons envisaged.
And even that 100,000-ton ambition had not yet materialized. When the Chinese plant opened in 2022, Calysseo was producing 20,000 tons per year, and it is unclear when full capacity is expected to be reached.
single-cell-protein-use-in-Aquaculture
Aquaculture is the most promising area for SCP use.Courtesy Iran Agricultural Ministry
A cautious approach
Although SCP has shown strong nutritional potential in aquaculture, wider adoption has been constrained by the difficulty of translating promising trials into large-scale commercial production, industry analysts believe.
"One important barrier is securing offtake agreements with aquafeed producers," said Dr. Waverly Eichhorst, research fellow at the Center for Feed Innovation.
Eichhorst explained that SCP producers need predictable demand to finance and operate large facilities, while feed manufacturers need confidence in consistent supply, product quality and pricing before committing to multiyear purchases.
"This creates a difficult cycle: production cannot scale without demand, but demand is unlikely to grow without predictable commercial-scale supply," Eichhorst added.
Commercial validation also remains limited.
"Feeding trials indicate that some SCPs can replace a meaningful share of fishmeal without compromising animal performance. However, feed manufacturers typically look for evidence across multiple species, formulations and production settings," Eichhorst said.
Eichhorst believes larger, longer-term commercial trials are needed to provide greater confidence in palatability, processing compatibility, product consistency, and economic performance under real farming conditions.
SCP broader adoption will depend on demonstrating consistent value at commercial scale, agreed Dr. Rebecca Delles, Alltech innovation business manager.
"Key considerations include production cost and scale, consistency of nutrient composition, digestibility and amino-acid availability, regulatory approval, quality assurance, and reliable supply," Delles said.
In addition, SCP is not one uniform ingredient, which can offer a range of different products to customers but also confuse the potential buyers.
"Products derived from yeast, bacteria, fungi or algae may differ substantially in nutritional characteristics, functional benefits and suitability by animal species," Delles said.
Delles also noted that feed manufacturers and livestock producers will require species-specific evidence showing that an ingredient performs consistently, integrates effectively into existing formulations and provides an economically competitive return.
In aquaculture, which is believed to be the most promising segment for SCP in the short to medium term, manufacturers are still reluctant to embrace it due to relatively high costs, according to Wasseem Emam, founder and head of research at Ethical Seafood Research.
"Producers watch the price per unit of digestible protein very closely," Emam said.
Emam added that SCP protein has struggled to compete with fishmeal and soy on that measure, particularly for price-sensitive commodity species such as tilapia and carp.
"Alongside cost sits scale. Very few plants run at anything like the volumes the aquafeed market needs, so formulators cannot rely on steady, large-volume supply and are reluctant to design it into their recipes," Emam said.
On top of that, he added, there are also technical hurdles around consistency and palatability across species and life stages, plus regulatory approval that varies market by market and can slow novel ingredients considerably.
"Add a few high-profile ventures that have stalled, and buyers understandably stay cautious," Emam said.
Multiple studies are aimed at importing SCP production technologies.Courtesy Jamie Turner | Frederick National Laboratory
Beyond the hype, SCP faces a more modest future
The future of SCP is likely to be less revolutionary than once imagined — but that does not mean it will be insignificant. Rather than replacing conventional protein sources, SCP is expected to carve out a role alongside them, observers say.
Center for Feed Innovation's Eichhorst believes that in the coming years SCP adoption is likely to remain concentrated in applications where its nutritional, environmental or supply-chain benefits create the greatest commercial value.
"SCPs are more likely to become established complementary ingredients than full replacements for conventional proteins across the wider feed market," said Eichhorst, assuming that the ingredient still has the strongest potential in aquaculture and pet food production.
"By contrast, it will be much more challenging for SCPs to compete with soybean meal and other low-cost proteins in bulk livestock feed," Eichhorst said. "Even substantial growth in SCP production would represent only a small share of global feed protein demand."
While several ambitious SCP projects in Western markets have stalled or failed to reach their planned scale, Eichhorst said, a new project in Saudi Arabia could offer the sector a way out of its commercial deadlock. The planned 50,000-ton-a-year facility brings together several of the conditions that have proved difficult to align elsewhere, including secure feedstock, an established industrial site and strong national interest in food security, Eichhorst added.
If successfully commissioned, the project could demonstrate how the ingredient can be integrated into an established feed supply chain at commercial scale.
Single-cell protein struggles to get out of the lab.Courtesy MicroHarvest
Alltech also expects slow but steady growth in SCP adoption in the feed industry in the coming years.
"The earliest and strongest opportunities are likely to be in applications where the ingredient offers value beyond crude protein alone," Delles said. "For example, a distinctive amino acid profile, high digestibility, consistent quality, functional properties or reduced dependence on constrained raw materials."
As a result, Delles said, higher-value sectors and applications that can support premium ingredient economics may therefore progress more quickly than broad replacement in commodity livestock diets.
Delles assumed that whether single-cell protein becomes mainstream will ultimately depend on the ability of individual technologies to scale production, achieve regulatory approval, demonstrate repeatable animal performance outcomes and compete economically with established ingredients.
"We hypothesize the category developing through targeted applications first, with broader adoption possible as production efficiency, evidence and supply availability improve," Delles added.
