Where Is Chlorella Found and Where Is It Grown?

Chlorella grows wild in freshwater ponds, lakes, damp soil, and even inside the cells of other organisms on every continent, and it is commercially cultivated in countries across Asia, Europe, and the Americas using systems that range from sunlit open ponds to sealed indoor fermenters. This single-celled green alga is one of Earth’s most widespread photosynthetic microorganisms, which is part of what made it attractive for large-scale farming in the first place. But where it lives in the wild and where humans choose to grow it are two different stories, shaped by very different pressures.

Wild Chlorella Lives Almost Everywhere There Is Moisture

Chlorella species are found in nearly all terrestrial and aquatic environments, from tropical rivers to cold temperate ponds, from moist tree bark to waterlogged agricultural soil.¹ The genus has been documented in freshwater bodies on every continent where researchers have gone looking. What makes Chlorella especially resilient is its small size (typically a few micrometers across), its tough cell wall, and its ability to survive periods of nutrient scarcity or drying. A damp patch of soil, a garden puddle, the surface film on a slow-moving stream, or the walls of an old water tank can all host Chlorella populations. The alga does not require pristine conditions; it thrives in nutrient-rich water and is commonly found in eutrophic ponds where nitrogen and phosphorus levels run high.

One of the more striking places wild Chlorella turns up is inside other organisms. Chlorella-like algae live as endosymbionts within the cells of Paramecium bursaria, a common freshwater ciliate, and within the tissues of Hydra viridis, a small freshwater animal related to jellyfish.² In these partnerships, the algal cells photosynthesize inside the host, sharing nutrients in return for shelter. Research on the Paramecium-Chlorella system has shown that this closed nutrient recycling helps both partners survive under conditions where nitrogen and prey are scarce.³ These symbiotic relationships are observed across many eukaryotic lineages, suggesting they have evolved independently multiple times, which hints at how ecologically versatile Chlorella and its relatives are.

How Chlorella Went from Pond Water to Pilot Plant

The first Chlorella species were isolated in 1890 by the Dutch microbiologist Martinus Willem Beijerinck from ponds near his city. Chlorella was among the first single-celled algae to be grown in pure laboratory culture, which is why it became a standard model organism for studying photosynthesis in the early twentieth century. But the jump from lab curiosity to potential food source came after World War II. Between 1947 and 1948, American scientists began seriously considering algae as a food source, with Chlorella standing out because it could be grown under controlled conditions.⁴ The Carnegie Institution supported further investigation, and by February 1951, Arthur D. Little Inc. had set up a large-scale Chlorella pilot plant in Cambridge, Massachusetts.

Japan developed its own Chlorella industry around the same time, driven partly by post-war food shortages and partly by parallel scientific interest. By the 1960s and 1970s, commercial Chlorella production had become established in Japan, Taiwan, and South Korea. Today, Asia still dominates global Chlorella production, but cultivation has spread to facilities in Germany, the United States, Australia, Brazil, and several other countries. The crop moved with the science, and the science followed the climate.

Open Ponds and the Tropics

The simplest and cheapest way to grow Chlorella commercially is in open raceway ponds: shallow, oval-shaped channels where the culture is circulated by a paddle wheel and grows under natural sunlight. These systems work best in warm climates with long daylight hours and relatively stable weather, which is why much of the world’s open-pond Chlorella production is located in tropical and subtropical regions across Southeast Asia, southern China, and parts of the Americas.

Open ponds have been tested in extreme environments too. In arid desert regions, Chlorella pyrenoidosa has been successfully cultivated outdoors in raceway ponds using domestic wastewater as a growth medium, with temperatures fluctuating between 18 and 31°C and abundant solar radiation exceeding 2,000 kilowatt-hours per square meter annually.⁵ Those conditions gave good results, but the arid-climate advantage of plenty of sunshine comes with its own water-management challenges.

Tropical climates offer warmth and light but create other problems. Open ponds in the Philippines, for instance, suffered culture crashes during the rainy season. In one study, a storm detached the sliding roof over the ponds, and the resulting contamination with rainwater killed the culture almost immediately.⁶ Heavy rain dilutes the culture, disrupts nutrient concentration, and introduces wild organisms that can outcompete or eat the Chlorella. Greenhouse enclosures help, but they add cost and engineering complexity, which partly explains why open-pond production in the tropics has not scaled as easily as it might seem.

Closed Photobioreactors and Temperate Climates

Closed systems, usually called photobioreactors, keep the Chlorella culture sealed inside transparent glass or plastic tubes, flat panels, or columns. Light passes through the walls, and environmental variables like temperature, carbon dioxide levels, and contamination risk are far more controllable than in an open pond. This makes photobioreactors the preferred option in temperate and northern climates where outdoor conditions are less cooperative.

Germany is a good example. Researchers there have grown Chlorella vulgaris in large-scale commercial photobioreactors holding up to 36,000 liters, comparing lab results with real production-season data from sunlit outdoor modules.⁷ Even in a climate with shorter days and cooler temperatures than the tropics, photobioreactors can produce commercially viable yields, though the economics are tighter because the hardware costs more per unit of biomass.

One of the clearest trade-offs is the energy bill. Modeling studies comparing outdoor and indoor photobioreactor operations have found that average algae productivity indoors can be roughly three times higher than outdoors, partly because indoor systems stabilize temperature and light.⁸ But that productivity gain has to be weighed against the heating and cooling costs of maintaining ideal temperatures year-round, along with the cost of the reactor hardware itself. In practice, many producers use greenhouses that split the difference: the culture is enclosed to prevent contamination, but natural sunlight provides most of the energy. Artificial intelligence and image-processing tools are also being explored to optimize tubular photobioreactor operations by monitoring culture health in real time.⁹

Fermentation in the Dark

Perhaps the most counterintuitive place Chlorella is grown is in the dark. While Chlorella is a photosynthetic organism, several species and strains can also grow heterotrophically, meaning they consume an external carbon source like glucose or acetic acid instead of using light energy. This ability opens the door to fermenter-based production, which looks more like brewing beer than farming algae.

Chlorella vulgaris has been grown heterotrophically in fed-batch fermenters ranging from 50 to 600 liters, using glucose as the carbon and energy source and urea for nitrogen, at a controlled temperature of around 36°C.¹⁰ Fermentation produces high-density cultures far more concentrated than anything achievable in an open pond. The trade-off is the cost of the sugar feedstock, which makes fermented Chlorella more expensive to produce than sun-grown Chlorella but gives it some advantages: the process can run anywhere regardless of climate, it runs 24 hours a day, and the sterile fermenter environment eliminates contamination risk.

Heterotrophic growth is not new. A fast-growing strain of Chlorella regularis was isolated from a pond and characterized for heterotrophic cultivation as early as the 1970s, with researchers finding it could use glucose, galactose, acetic acid, and ethanol as carbon sources in both light and dark conditions.¹¹ Today, some of the Chlorella sold as nutritional supplements or cosmetic ingredients comes from fermenter production, particularly when manufacturers need tight control over the biochemical composition of the final product.

What Chlorella Needs to Grow Well

Regardless of the cultivation system, Chlorella needs a few basics: a carbon source (carbon dioxide in photosynthetic systems, sugar in fermenters), nitrogen, phosphorus, light (if growing phototrophically), and a temperature window that varies by species but generally falls between about 20 and 36°C. The balance of nitrogen to phosphorus matters considerably. Research on Chlorella vulgaris has shown that when the nitrogen-to-phosphorus ratio sits around 10:1, complete removal of both nutrients can be achieved alongside strong growth, but dropping nitrogen below about 2.5 milligrams per liter cuts the growth rate by roughly four-fifths and reduces maximum biomass more than threefold.¹²

Carbon dioxide supplementation is standard in commercial photobioreactors. Some facilities pipe in industrial CO₂, and there has been interest in using flue gas directly from coal power plants. Research on Chlorella fusca grown on flue gas found that the algae’s tolerance to elevated temperatures is an important factor for reducing gas-cooling costs, since the exhaust can be injected directly into the bioreactors without extensive cooling first.¹³ This dual benefit of carbon capture and biomass production has made industrial CO₂ integration a recurring theme in Chlorella research.

Contamination and Predators

The biggest headache for anyone growing Chlorella at scale, especially in open ponds, is contamination. Wild organisms find their way into the culture, and some of them eat Chlorella or outcompete it for nutrients. One detailed survey of outdoor Chlorella raceway ponds in Arizona identified nineteen distinct contaminating organisms, including two fungi, seven flagellates, three amoebae, four ciliates, one rotifer, and two large insects. Among these, a small flagellate called Poterioochromonas was singled out as especially destructive, capable of triggering complete culture collapse.¹⁴

Predatory flagellates and ciliates are the two most common groups of biological contaminants in Chlorella mass culture.¹⁵ Producers use a range of countermeasures, including adjusting pH, briefly raising the temperature, applying low-concentration surfactants, or using ultrasonic pulses to kill grazers without harming the algae. Closed photobioreactors and fermenters largely avoid these problems, which is one reason producers are willing to pay more for sealed systems despite the higher capital costs.

Heavy metal contamination is another concern, particularly when Chlorella is grown on wastewater or in areas with polluted water sources. Research has shown that Chlorella vulgaris responds differently to different metals: its growth is more sensitive to arsenic, zinc, and lead, while its photosynthesis is more affected by copper and nickel. At lower copper concentrations, the algae form mucilaginous clumps as a defense mechanism.¹⁶ For supplement-grade Chlorella, this means the quality of the water source and growing medium must be monitored carefully, since the alga can absorb pollutants from its environment.

Chlorella in Wastewater Treatment

Chlorella’s appetite for nitrogen and phosphorus has made it a candidate for wastewater treatment, where the goal is to strip nutrients from sewage or industrial effluent before discharging it. This is not just a side application; a substantial body of research frames Chlorella cultivation as a way to clean water while simultaneously producing useful biomass.

In municipal settings, co-cultivating Chlorella vulgaris with activated sludge (the microbe-rich slurry already used in conventional sewage treatment) has shown clear benefits over sludge alone. One study found that adding Chlorella to the process improved removal of chemical oxygen demand by about 1.4-fold, total phosphorus by about 1.7-fold, and ammonium nitrogen by about 1.4-fold, while also capturing more biogenic CO₂ than the standard treatment process.¹⁷ Other research supports the broader potential of integrating native Chlorella strains into real wastewater treatment systems as a strategy for promoting environmental sustainability.¹⁸

The limitation is that biomass produced from wastewater is generally not suitable for food or supplement use due to contamination concerns. It can, however, be directed toward biofuel production, animal feed, or soil amendments. Chlorella vulgaris grown on vineyard wastewater, for instance, achieved strong biomass output while reducing chemical oxygen demand and polyphenol content by over 92%.¹ So where Chlorella is grown sometimes depends on what the biomass will be used for: food-grade algae comes from clean water in controlled systems, while waste-treatment algae comes from dirty water and gets used for non-food purposes.

Breaking Open the Cell Wall

One reason Chlorella’s cultivation geography and method matter so much is that the alga’s thick cell wall makes post-harvest processing a significant challenge. The cell wall locks in the proteins, carbohydrates, and other nutrients that make Chlorella valuable as a supplement. If you eat Chlorella without first breaking the wall, your body absorbs much less of its nutritional content.

Research comparing different wall-disruption methods found that alkali-catalyzed hydrolysis was especially effective for Chlorella vulgaris, solubilizing up to about 56% of the total biomass as protein and about 14% as carbohydrates.¹⁹ Mechanical methods like bead milling and high-pressure homogenization are also common at industrial scale. The “cracked cell wall” label you see on many Chlorella supplements refers to this processing step, and it is one reason supplement-grade Chlorella tends to be more expensive than the raw dried powder. Producers who use fermenters sometimes achieve slightly different cell-wall compositions depending on the carbon source and growth conditions, which can affect how easily the wall breaks down during processing.

The Taxonomy Problem

When researchers or supplement companies say “Chlorella,” they may not be talking about the same organism. The genus Chlorella has a serious identity crisis. Molecular phylogenetic analysis has confirmed that the genus is polyphyletic, meaning that organisms historically lumped together as Chlorella based on their appearance actually belong to several unrelated evolutionary lineages.²⁰ A “true” Chlorella clade includes the type species C. vulgaris along with C. variabilis, C. heliozoae, and a handful of others, but species like C. sorokiniana, C. lewinii, and C. thermophila have been found to belong to different groups entirely.

Making matters worse, even within the true Chlorella clade, cryptic diversity is high. That means strains that look identical under a microscope can be genetically distinct species with different physiological and biochemical properties. One study using genetic fingerprinting of Chlorella vulgaris isolates found five cryptic species among just eleven tested genotypes, leading the authors to stress the importance of carefully recording which strain is used in any experiment or commercial application, since genomic variation may correspond to real differences in how the organism behaves.²¹

For consumers, this means the Chlorella in one brand of supplements may be a genuinely different organism from the Chlorella in another, even if both labels say “Chlorella vulgaris.” For researchers, it means that findings from one strain cannot be automatically assumed to apply to another. And for producers, it means that the strain they select for cultivation can significantly affect growth rate, nutrient profile, and cell-wall composition. Geography and taxonomy interact here: a Chlorella strain isolated from a tropical pond in Indonesia will likely behave differently from one isolated from a temperate European lake, even if both end up classified under the same species name.

Chlorella in Space

If the question is where Chlorella could be grown in the future, one answer is off-planet. Microalgae, including Chlorella, are among the most promising organisms for bioregenerative life support systems designed for long-duration space missions. Their appeal comes from doing three jobs at once: consuming carbon dioxide, producing oxygen, and generating edible biomass rich in protein, lipids, and carbohydrates.²²

Recent work has tested how Chlorella vulgaris performs under simulated lunar gravity and microgravity conditions. Researchers estimated the culture volumes needed to supply the daily protein, carbohydrate, and lipid requirements for a six-person crew, using productivity figures from simulated space-like conditions.²³ Other researchers have explored immobilizing Chlorella cells in calcium alginate beads, a technique that reduces the amount of liquid needed and makes harvesting easier in zero gravity. In batch flask tests, immobilized Chlorella reached a dry weight of about 0.93 grams per liter and contained up to roughly a third lipids and about a quarter protein by dry weight, demonstrating reasonable nutritional value even with reduced productivity compared to free-swimming cultures.²⁴ The engineering challenges remain significant, but Chlorella’s hardiness and versatility keep it near the top of the candidate list for space agriculture.

Chlorella as a Soil Amendment

Back on Earth, one growing application that ties the “found” and “grown” stories together is using cultivated Chlorella biomass to improve agricultural soil. Wild Chlorella already contributes to soil ecosystems in a small way, but applying concentrated Chlorella biomass as a biofertilizer can enhance nutrient levels in soil, improve water retention, and foster healthier crop growth. Chlorella vulgaris and Spirulina platensis have been studied as biofertilizers for rice cultivation, where their improvement of the soil’s biological and chemical properties had a positive effect on plant growth.¹ This creates a circular-economy pathway: Chlorella grown on wastewater removes pollutants, and the resulting biomass gets returned to agricultural land as fertilizer, closing the nutrient loop. Whether that loop becomes economically practical at scale is still an open question, but the biology works.