Algae: What properties are exploited?


Many kelps are largely indigestible. Inert material for delivery of medicinals.


Diatom fossils used embalming compounds, enamel polishes. Diatomaceous bricks ordered by Emperor Justinian to build the dome of the church of Hagia Sophia in Istanbul in AD 532.
Reduces glossiness in paint.


Diatom fossils (Bacillariophyceae Limestone – diatomaceous earth) used to filter sugar cane liquors since 1914; to filter sewage in UK since 1976; pet litter. 68% of product used in filter aids, especially water purification.

Nobel stabilized nitroglycerine. Used in match heads, to control cigar burning, and as anticaking agents in dried foods.

Colloidal form:

alginates, agar and carrageenans are thickening agents (fruit drinks and salad dressing), colloid stabilizers in food (ice creams, sherbets and cheeses), textile, cosmetic, pharmaceutical, paper and welding industries. Carrageenan preferred over agar to stabilize emulsions in paints, cosmetics and dairy products. Improves quality of soups, salad dressings, sauces, fruit drinks, etc.. Clarifying and stabilizing agent for beer. Assists in suspension of cocoa particles in milk chocolate. Used in ice cream to prevent migration of colours in multi-coloured ices. Known for a long time as a constituent of jellies and desserts.

Forms gels:

water retention and absorption, agar for capsules for medication, dental impressions, cosmetic base, microbiological medium, biochemistry – electrophoresis, anti- drying agent in bakery goods, rapid-setting jellies and desserts, temporary meat and fish preserved in tropics. Desserts, sauces, soups and jellies in Europe, North America, Japan and China. Thickening agent emulsifier and stabilizer for sauces mayonnaise, cakes, beer cheese, ice creams and candies. Agar’s first use discovered by Frau Franny Eilshemius (a physician’s wife) whose husband told Robert Koch, who is credited with the discovery!


Soil amendment: – Records as animal manure substitute since 5th century AD. Charles II allowed people to collect for fertilizer. Easement of ox-cart’s width allowed and show in records of Rhode Island. Chlamydomonas and other soil algae make mucilages that loosen compacted soil. Used on compacted ash of Mt. St Helens to restore farming.

Chemical composition:


Spirulina – blue-green used for food in old (Lake Chad) and new world (Aztecs before conquistadores) – protein supplement (72% of dry weight). 10 tons per acre (wheat – 0.16 ton per acre; cattle 0.16 ton per acre. A bit low in S- amino acids but superior to all plant protein sources and equal to meat or dairy products. Christopher Hills (UK) – dried alga for chicken feed with high protein and high carotene. Imperial Valley California and Kona coast of Hawaii using ponds in saline soil


Harvested for ash Na, K.; Vitamin C can equal citrus. Rich in vitamins A, D, B, B12, E, riboflavin, niacin, and pantothenic and folic acids, Table on page 622 of Simpson contains food values of commonly eaten algae, Undaria (qundai-cai – China; wakame – Japan) enhances calcium uptake from gut, promotes bone formation


Fertilizers: – rich in potassium and nitrogen but low in phosphate. Good complement to animal which is high in phosphate, equal in N and only 1/3 as rich in phosphate. Some liquid fertilizers are prepared from kelps and mixed seaweed collections. Some field tests have shown that these liquid fertilizers may increase legume yield.

The poor digestibility, including by microbes, makes bulk seaweed useful as a soil conditioner. In addition it is largely free of terrestrial weeds and fungi.

Anabaena sp. (Cyanobacteria) form a symbiotic relationship with the aquatic fern, Azolla. The cultivation of this symbiosis in rice paddies is the so-called “green manure”. Inoculation of 0.2 kg of Azolla per hectare is equivalent to 30 kg/hectare of commercial nitrogen fertilizer. Not as popular now because Azolla growth is limited by phosphate, which is non-renewable. Next break is low-phosphorus requiring Azolla.

Chlorella is reported as the only microscopic green alga used commercially (uses not recorded in my sources). The mucilaginous properties of Chlamydomonas have been exploited to loosen compacted soil. Used on compacted ash of Mt. St. Helens to restore farming.

The alkaline properties of crushed calcareous algae have been exploited in Europe and N. Africa as a means to reduce soil acidity.

Biochemical activity:

Details of waste treatment (see Simpson, page 641) . Tertiary treatment can use algal – bacterial culture + light + sewage leads to bio-oxidation. Produces precipitated organic material (sludge) plus oxygen which maintains aerobic bacteria. Organisms absorb N and P from sewage for their own use. With photosynthetic oxidation BOD drops 90% and P drops 80% . Get some examples (check Iona, but Simpson quotes Hollister, CA.

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