Algaculture
Algaculture is a form of aquaculture involving the farming of species of algae.
The majority of algae that are intentionally cultivated fall into the category of microalgae. Macroalgae, commonly known as seaweed, also have many commercial and industrial uses, but due to their size and the specific requirements of the environment in which they need to grow, they do not lend themselves as readily to cultivation.
Commercial and industrial algae cultivation has numerous uses, including production of nutraceuticals such as omega-3 fatty acids or natural food colorants and dyes, food, fertilizers, bioplastics, chemical feedstock, protein-rich animal/aquaculture feed, pharmaceuticals, and algal fuel, and can also be used as a means of pollution control and natural carbon sequestration.
Global production of farmed aquatic plants, overwhelmingly dominated by seaweeds, grew in output volume from 13.5 million tonnes in 1995, to just over 30 million tonnes in 2016 and 37.8 million tonnes in 2022. This increase was the result of production expansions led by China, followed by Malaysia, the Philippines, the United Republic of Tanzania, and the Russian Federation.
Cultured microalgae already contribute to a wide range of sectors in the emerging bioeconomy. Research suggests there are large potentials and benefits of algaculture for the development of a future healthy and sustainable food system.
- News article about the study:
Uses of algae
Food
Several species of algae are raised for food. While algae have qualities of a sustainable food source, "producing highly digestible proteins, lipids, and carbohydrates, and are rich in essential fatty acids, vitamins, and minerals" and e.g. having a high protein productivity per acre, there are several challenges "between current biomass production and large-scale economic algae production for the food market".- Micro-algae can be used to create microbial protein used as a powder or in a variety of products.
- Purple laver is perhaps the most widely domesticated marine algae. In Asia it is used in nori and gim. In Wales, it is used in laverbread, a traditional food, and in Ireland it is collected and made into a jelly by stewing or boiling. Preparation also can involve frying or heating the fronds with a little water and beating with a fork to produce a pinkish jelly. Harvesting also occurs along the west coast of North America, and in Hawaii and New Zealand.
- Algae oil is used as a dietary supplement as the plants also produce Omega-3 fatty acids, which are commonly also found in fish oils, and which have been shown to have positive health benefits, including for cognition and against brain aging.
- Dulse is a red species sold in Ireland and Atlantic Canada. It is eaten raw, fresh, dried, or cooked like spinach.
- Spirulina is a blue-green microalgae with a long history as a food source in East Africa and pre-colonial Mexico. Spirulina is high in protein and other nutrients, finding use as a food supplement and for malnutrition. Spirulina thrives in open systems and commercial growers have found it well-suited to cultivation. One of the largest production sites is Lake Texcoco in central Mexico. The plants produce a variety of nutrients and high amounts of protein. Spirulina is often used commercially as a nutritional supplement.
- Chlorella, another popular microalgae, has similar nutrition to spirulina. Chlorella is very popular in Japan. It is also used as a nutritional supplement with possible effects on metabolic rate.
- Irish moss, often confused with Mastocarpus stellatus, is the source of carrageenan, which is used as a stiffening agent in instant puddings, sauces, and dairy products such as ice cream. Irish moss is also used by beer brewers as a fining agent.
- Sea lettuce, is used in Scotland, where it is added to soups and salads.
- Dabberlocks or badderlocks is eaten either fresh or cooked in Greenland, Iceland, Scotland and Ireland.
- Aphanizomenon flos-aquae is a cyanobacteria similar to spirulina, which is used as a nutritional supplement.
- Extracts and oils from algae are also used as additives in various food products.
- Sargassum species are an important group of seaweeds. These algae have many phlorotannins.
- Cochayuyo is eaten in salads and ceviche in Peru and Chile.
- Both microalgae and macroalgae are used to make agar, which is used as a gelling agent in foods.
Lab manipulation
Agar
Both microalgae and macroalgae are used to make agar.Fertilizer
For centuries seaweed has been used as fertilizer. It is also an excellent source of potassium for manufacture of potash and potassium nitrate. Some types of microalgae can be used this way as well.Pollution control
With concern over global warming, new methods for the thorough and efficient capture of CO2 are being sought out. The carbon dioxide that a carbon-fuel burning plant produces can feed into open or closed algae systems, fixing the CO2 and accelerating algae growth. Untreated sewage can supply additional nutrients, thus turning two pollutants into valuable commodities.Waste high-purity as well as sequestered carbon from the atmosphere can be used, with potential significant benefits for climate change mitigation.
Algae cultivation is under study for uranium/plutonium sequestration and purifying fertilizer runoff.
Energy production
Business, academia and governments are exploring the possibility of using algae to make gasoline, bio-diesel, biogas and other fuels. Algae itself may be used as a biofuel, and additionally be used to create hydrogen.Microalgae are also researched for hydrogen production – e.g. micro-droplets for algal cells or synergistic algal-bacterial multicellular spheroid microbial reactors capable of producing oxygen as well as hydrogen via photosynthesis in daylight under air.
Microgeneration
Carbon sequestration
Other uses
Chlorella, particularly a transgenic strain which carries an extra mercury reductase gene, has been studied as an agent for environmental remediation due to its ability to reduce to the less toxic elemental mercury.Cultured strains of a common coral microalgal endosymbionts are researched as a potential way to increase corals' thermal tolerance for climate resilience and bleaching tolerance.
Cultured microalgae is used in research and development for potential medical applications, in particular for microbots such as biohybrid microswimmers for targeted drug delivery.
Cultivated algae serve many other purposes, including cosmetics, animal feed, bioplastic production, dyes and colorant production, chemical feedstock production, and pharmaceutical ingredients.
Growing, harvesting, and processing algae
Monoculture
Most growers prefer monocultural production and go to considerable lengths to maintain the purity of their cultures. However, the microbiological contaminants are still under investigation.With mixed cultures, one species comes to dominate over time and if a non-dominant species is believed to have particular value, it is necessary to obtain pure cultures in order to cultivate this species. Individual species cultures are also much needed for research purposes.
A common method of obtaining pure cultures is serial dilution. Cultivators dilute either a wild sample or a lab sample containing the desired algae with filtered water and introduce small aliquots into a large number of small growing containers. Dilution follows a microscopic examination of the source culture that predicts that a few of the growing containers contain a single cell of the desired species. Following a suitable period on a light table, cultivators again use the microscope to identify containers to start larger cultures.
Another approach is to use a special medium which excludes other organisms, including invasive algae. For example, Dunaliella is a commonly grown genus of microalgae which flourishes in extremely salty water that few other organisms can tolerate.
Alternatively, mixed algae cultures can work well for larval mollusks. First, the cultivator filters the sea water to remove algae which are too large for the larvae to eat. Next, the cultivator adds nutrients and possibly aerates the result. After one or two days in a greenhouse or outdoors, the resulting thin soup of mixed algae is ready for the larvae. An advantage of this method is low maintenance.