Algaculture

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 (this may change, however, with the advent of newer seaweed cultivators, which are basically algae scrubbers using upflowing air bubbles in small containers, known as tumble culture).

[2] Commercial and industrial algae cultivation has numerous uses, including production of nutraceuticals such as omega-3 fatty acids (as algal oil)[3][4][5] or natural food colorants and dyes, food, fertilizers, bioplastics, chemical feedstock (raw material), protein-rich animal/aquaculture feed, pharmaceuticals, and algal fuel,[6] and can also be used as a means of pollution control and natural carbon sequestration.

[8][9] This increase was the result of production expansions led by China, followed by Malaysia, the Philippines, the United Republic of Tanzania, the Russian Federation.

[10] Research suggests there are large potentials and benefits of algaculture for the development of a future healthy and sustainable food system.

[7] Australian scientists at Flinders University in Adelaide have been experimenting with using marine microalgae to produce proteins for human consumption, creating products like "caviar", vegan burgers, fake meat, jams and other food spreads.

[53][54][55] Cultured microalgae is used in research and development for potential medical applications, in particular for microbots[56] such as biohybrid microswimmers for targeted drug delivery.

In a typical algal-cultivation system, such as an open pond, light only penetrates the top 3 to 4 inches (76–102 mm) of the water, though this depends on the algae density.

Paddle wheels can stir the water and compressed air coming from the bottom lifts algae from the lower regions.

Glow plates made from sheets of plastic or glass and placed within the tank offer precise control over light intensity, and distribute it more evenly.

The odor associated with bogs, swamps, and other stagnant waters can be due to oxygen depletion caused by the decay of deceased algal blooms.

Under anoxic conditions, the bacteria inhabiting algae cultures break down the organic material and produce hydrogen sulfide and ammonia, which causes the odor.

These chemicals are detectable at very low levels – in the parts per billion range – and are responsible for many "taste and odor" issues in drinking water treatment and distribution.

Silica and iron, as well as several trace elements, may also be considered important marine nutrients as the lack of one can limit the growth of, or productivity in, a given area.

The seven most cultivated taxa are Eucheuma spp., Kappaphycus alvarezii, Gracilaria spp., Saccharina japonica, Undaria pinnatifida, Pyropia spp., and Sargassum fusiforme.

Eucheuma and K. alvarezii are attractive for carrageenan (a gelling agent); Gracilaria is farmed for agar; the rest are eaten after limited processing.

For instance, Dunaliella salina grow in extremely salty water; these unusual media exclude other types of organisms, allowing the growth of pure cultures in open ponds.

Open culture can also work if there is a system of harvesting only the desired algae, or if the ponds are frequently re-inoculated before invasive organisms can multiply significantly.

The chain diatoms are held in the bag and feed shrimp larvae (in Eastern hatcheries) and inoculate new tanks or ponds.

Seaweed farming industry serves commercial needs for various products such as food, feed, pharma chemicals, cosmetics, biofuels, and bio-stimulants.

Open sea cultivation method involves the use of rafts or ropes anchored in the ocean, where the seaweed grows attached to them.

First, a suitable site in the ocean is identified, based on factors such as water depth, temperature, salinity, and nutrient availability.

Once a site is chosen, ropes or rafts are anchored in the water, and the seed pieces of seaweed are attached to them using specialized equipment.

The pond is typically lined with a synthetic material, such as polyethylene (HDPE) or polyvinyl chloride, to prevent the loss of water and nutrients.

[75] High-Rate Algal Ponds (HRAPs) are a type of open algae cultivation system that has gained popularity in recent years due to their efficiency and low cost of operation.

The ponds are equipped with a paddlewheel or other type of mechanical agitation system that provides mixing and aeration, which promotes algae growth.

Virtually any translucent container could be called a PBR; however, the term is more commonly used to define a closed system, as opposed to an open tank or pond.

V-shaped plastic bags are effective for growing a variety of algae species, including Chlorella, Spirulina, and Nannochloropsis.

Operation of plastic bags is tedious as they need to be replaced after every use to maintain the sterility, which is a laborious task for large scale facility.

In this method, oils from the algae are extracted through repeated washing, or percolation, with an organic solvent such as hexane or petroleum ether, under reflux in a special glassware.

In this method, CO2 is liquefied under pressure and heated to the point that it becomes supercritical (having properties of both a liquid and a gas), allowing it to act as a solvent.