Humanity has a great deal to thank algae for. Phytoplankton are responsible for producing at least half of the Earth’s oxygen and one out of every two breaths we take is made possible by these microscopic marine creatures.
But their contribution doesn’t stop at oxygen. Algae are rapidly emerging as a biological powerhouse with the potential to address some of humanity’s most urgent challenges. Whether it’s producing low-impact animal feed, enabling renewable electricity, or development of sustainable building materials, algae offer scalable solutions deeply aligned with a resource-efficient future.
This article unpacks the fundamentals of algae, explores its diverse real-world applications, and examines the barriers and opportunities involved in scaling and commercializing algae-based solutions to achieve the net-zero goals.
What is Algae?
Algae are a diverse group of photosynthetic organisms found in nearly all aquatic environments, from freshwater to the oceans. They form the foundation of aquatic ecosystems by serving as primary producers that support marine biodiversity.
Algae range in size from microscopic, single-celled microalgae (under 3 micrometers) to large, multicellular macroalgae like kelp, which can grow over 30 meters long. Beyond their ecological role, algae provide essential ecosystem services such as carbon capture, oxygen production, combating eutrophication, mitigating ocean acidification, and protecting shorelines. Functioning as natural bio-factories, algae convert carbon dioxide into valuable biomass, enabling climate-positive solutions across various sectors.
Different types of Algae
Algae are broadly classified into two types based on their size and habitat: microalgae and macroalgae (also known as seaweed). Together, they contribute significantly to the global carbon cycle and hold promise for decarbonizing industries in energy, agriculture, food, and materials, making them key players in climate mitigation efforts.
Microalgae
Microalgae are microscopic, single-celled organisms found in both freshwater and marine environments. They are rich in bioactive compounds such as pigments, proteins, and lipids, and can be used in a range of applications including food, feed, cosmetics, pharmaceuticals, and biofuels.
- Bulk components like proteins are used in starchy food like bread, cookies, while lipids can be used as health supplements or biofuels.
- High-value compounds such as pigments can be used as natural colorants and omega-3 fatty acids offer a sustainable alternative to fish oils.
- Alternative protein source for both human consumption and animal feed, thanks to their ability to accumulate high concentrations of essential nutrients like iodine.
Different types of single celled and filamentous microalgae species.
Image courtesy: Unicellular microalgae vs. filamentous algae for wastewater treatment and nutrient recovery
As photosynthetic organisms, microalgae convert sunlight, atmospheric CO₂, and nutrients from aquatic media into biomass without requiring arable land or freshwater. Remarkably, they can utilize industrial flue gases with CO₂ concentrations up to ten times higher than terrestrial plants, making them efficient tools for carbon sequestration and climate mitigation.
Macroalgae
Macroalgae, commonly known as seaweeds, are larger multicellular algae found in marine environments, typically growing on rocks and other hard surfaces along coastlines. They thrive in a range of marine habitats including intertidal rocky shores, coral reefs, and seagrass meadows and can be cultivated along anchored lines or nets.
Seaweeds form the largest vegetated marine ecosystems globally, covering an estimated 74% of all marine vegetated areas. They are integral to the functioning of global marine ecosystems, playing a critical role in nutrient cycling, habitat provisioning, and supporting rich biodiversity. Scaling up seaweed cultivation offers a promising approach to removing ocean-based carbon dioxide. By farming fast-growing species like kelp, carbon dioxide is absorbed during photosynthesis and sequestered within the algal biomass, providing an effective means for both carbon capture and sustainable resource production.
Seaweed in its natural habitat with other fish species thriving in its dense foliage.
Macroalgae have a broad array of commercial and industrial applications spanning food, agriculture, and biotechnology, making it a high-impact input for circular, low-carbon economies.
- Food Products: Seaweeds are consumed as vegetables (e.g., nori, kombu, wakame) and as ingredients in processed foods such as soups, noodles, teas, cheese, and even wine.
- Hydrocolloid Production: Extracts from seaweeds are used to produce hydrocolloids. Their gelling and thickening properties make them widely used in products like ice cream, jellies, and dairy alternatives, as well as in biotechnology, medicine, and cosmetics.
- Fertilizers and Soil Conditioners: Seaweed can be used as biofertilizers to improve crop yield, nutrient uptake, pest resistance, seed germination, and tolerance to environmental stresses. Both solid and liquid seaweed-based products are commercially available and popular in organic farming. As a fast-growing, protein-rich crop, seaweed is being used in and as a methane-reducing feed additive for livestock. Some species yield five times more protein per unit area than soybeans.
- Bioplastics and Textiles: Startups are creating compostable packaging, thin films, and even fibers for apparel, leveraging the renewable and low-carbon nature of seaweed.
- Wastewater Treatment and Environmental Remediation: Seaweed is used to remove excess nutrients (nitrogen, phosphorus) and heavy metals from wastewater, benefiting both aquaculture systems and broader environmental management.
Challenges in scaling algae cultivation
Algae cultivation faces critical hurdles when moving from laboratory to commercial scale, whether on land or in the ocean. While land-based systems offer precise quality and biosecurity control, their high costs and resource demands limit commercial scalability. This has driven interest in ocean-based approaches, which can access greater natural resources and scale but introduce their own operational and environmental challenges.
High Infrastructure and Operational Costs
Land-based systems rely heavily on energy for lighting, mixing, temperature regulation, and cleaning, further raising operational costs. Large-scale algae production requires expensive infrastructure, such as photobioreactors (PBRs), open ponds, or fermenters. PBRs—necessary for high yields and biosecurity—are especially cost-prohibitive and typically reserved for premium products (e.g., nutraceuticals). What else, running advanced cultivation systems demands specialized personnel, ongoing technical oversight, and increased labor and maintenance costs.
Production Economics
Understanding the economic challenges of algae production is vital for assessing its commercial feasibility and identifying areas for cost reduction.
- High Biomass Costs: The cost of producing microalgae biomass is considerably higher than existing alternatives, estimated at €290–€570 per kilogram of dry weight, depending on the method. This undermines the ability to compete with established commercial products and fuels.
- Harvesting Difficulties: Microalgae’s small cell size makes harvesting particularly energy- and labor-intensive. Methods such as filtration, centrifugation, or flocculation must be tailored to specific species, and can account for 21% of total capital costs in open pond systems.
- Processing Constraints: Processing algae into usable products (e.g., biofuels) remains expensive, especially if co-production of high-value compounds (like pigments or pharmaceuticals) is not viable to offset costs.
Biological and Environmental Instability
Open pond cultivation is vulnerable to contamination by parasites, pathogens, and competing species, as well as challenges like nutrient imbalances, low CO₂ availability, limited light penetration at high cell densities, and daily pH swings—all of which reduce productivity and consistency.
In contrast, closed systems such as photobioreactors offer enhanced control over growth conditions and minimize contamination risks, resulting in higher yields. However, their high capital and operational costs limit scalability and profitability, particularly for low-value products like biofuels.
Regulatory and permitting hurdles slow down commercial deployment
Despite growing interest in algae as a sustainable resource, complex and lengthy regulatory and permitting processes remain major barriers to large-scale commercial deployment.
- Lengthy Approvals: Obtaining necessary permits often involves multiple agencies and overlapping domestic and international regulations. In the U.S., securing water bottom leases and completing environmental reviews can take 18 months to 5 years, with some processes extending up to 10 years.
- International Compliance: Large-scale seaweed projects, especially those linked to carbon sequestration or production of animal feed, fertilizer, and cosmetics, face additional scrutiny under international treaties like the London Convention and Protocol. These regulate marine pollution and restrict activities such as adding growth enhancers or releasing synthetic materials, increasing legal complexity as projects scale.
- Food Safety: Algae used in food and feed must comply with strict contaminant limits (e.g., iodine, arsenic, heavy metals). In the EU, varying limits across member states create a fragmented regulatory environment, complicating market access and competitiveness.
Environmental risks associated with unchecked algae overgrowth
Over-cultivating algae, especially in open marine environments, can result in unintended ecological consequences. One of the most significant risks is the outbreak of harmful algal blooms which can degrade water quality, disrupt ecosystems, and pose risks to both marine life and human health.
- Oxygen Depletion & Acidification: Excessive blooms deplete oxygen as algae decompose, causing dead zones and contributing to ocean acidification through CO₂ release.
- Harmful Blooms: Microalgae blooms can contaminate water and harm aquatic animals and humans, while macroalgae like Sargassum and Ulva (“golden” and “green tides”) damage coastlines and disrupt tourism and fisheries.
- Challenges in Biomass Removal: Managing large blooms is logistically difficult and expensive. Most excess biomass has limited commercial use and may be contaminated (e.g., with arsenic), restricting safe application in products like feed or fertilizer.
- Unsustainable Practices: Poorly managed seaweed farming can inadvertently fuel massive blooms, as seen in events like China’s Yellow Sea outbreak, with high removal costs and limited reuse options.
- Containment & Monitoring Gaps: Genetically modified algae pose additional ecological risks if accidentally released, demanding strict containment and monitoring.
- Nutrient Management Issues: Improper dosing and recycling of nutrients can lead to runoff, eutrophication, and further water pollution.
Without careful regulation and management, unchecked algae cultivation can cause harmful blooms, oxygen loss, and environmental damage, emphasizing the need for sustainable practices and effective oversight.
China’s Yellow Sea experienced its largest recorded algal bloom in 2008, as thick waves of green algae blanket the coastline and wash ashore. Image courtesy: The Telegraph
Unlocking algae’s full potential for a sustainable future
Algae has emerged as a versatile and scalable solution for global decarbonization, with applications ranging from carbon capture and wastewater treatment to alternative proteins and regenerative ocean farming. Startups worldwide are proving that algae-based innovations can be both commercially viable and ecologically impactful.
Though still an emerging sector within the blue bioeconomy, algae’s full climate potential depends on overcoming systemic challenges—high production and processing costs, regulatory hurdles, infrastructure constraints, and environmental risks. Addressing these requires continued innovation, strategic investment, and enhanced collaboration across industries.
As the world pursues resilient and regenerative growth, algae provides a promising pathway to replace fossil-based materials and accelerate global decarbonization efforts. Continue reading the next article in the Algae series to learn about the innovations in this space.
