The humble seaweed may best be known for its ability to encase morsels of sticky rice and raw fish (not to mention spa-goers), but this plant-like organism has slowly worked its way into an impressive variety of human industries over the past 15 centuries. Now one can find seaweed, or at least one of its many prized extracts, in everything from toothpaste to wound dressings.
What is seaweed
The term "seaweed" is a misnomer as the stuff we call seaweed is not a weed — in fact, it's not even a plant. Seaweed is actually one of three (occasionally four) broad groups of multicellular, marine algae. These ancient species are commonly sorted according to a 19th century taxonomy based on their colour: red, green, brown and blue-green.
Even though blue-green algae is actually colonies of cyanobacteria, given their tufted plant-like appearance, they are sometimes lumped in with the other three. Similarly, red and brown seaweeds are almost exclusively oceanic while green seaweeds are rarely found outside of freshwater. This wide range of habitats and stem from seaweed's ancient origins — it's among the oldest forms marine life and actually represents four of the six kingdoms of organisms.
While its difficult to accurately define what is and isn't a "seaweed", it's not hard to see the product's value to human society. Products employing seaweed and its extracts total about $US6 billion annually, $US5 billion of which comes from direct consumption of the algae as a foodstuff. The remaining billion bucks stems from the extraction of hydrocolloids from the plant matter for a variety of uses (which we'll get to in a second).
Current global estimates put seaweed harvests at around eight million tonnes annually, a vast majority of which is now cultivated rather than harvested from the wild. China is far and away the largest producer of cultured seaweed, raking in around five million wet tonnes of the stuff every year from hundreds of hectares of coastal nurseries.
The remaining three million tonnes or so comes from 34 other nations worldwide. And since seaweeds have adapted to grow in virtually any salty — or at least brackish — water, they can be commercially cultured virtually anywhere in the world from frigid subarctic waters to aquamarine Caribbean coasts. Roughly 90 per cent of the total annual harvest now comes from cultivated sources — largely because demand over the last half century has vastly outpaced naturally occurring supplies.
Don't call it a comeback, seaweed's been here for years
Seaweed has been a staple crop in east Asia for more than 2500 years. The earliest recorded references of seaweed exploitation date back to 6th century BC when Sze Teu wrote, "Some algae are a delicacy fit for the most honoured guests, even for the King himself." By the 8th century AD, a half dozen varieties of seaweed had made their way to Japan and, today, the island nation cultivates 21 separate species. The three most common of which are Nori (used to wrap sushi), Kombu (a ubiquitous soup stock ingredient) and Wakame (used largely in soups and salads).
Until recently, seaweed actually constituted as much as 10 per cent of the Japanese diet. Today, China, Japan and South Korea still consume the lion's share of seaweed, although the rapidly growing popularity of sushi has seen a spike in demand from the US, Europe and South America.
The nutritional value of seaweed cannot be understated. It's extremely rich in iodine, calcium, vitamin C (1.5 times as much as an orange), B12, even protein. It's high in fibre and low in fat. Seaweed was also a vital component to traditional Chinese cancer treatments and other medical treatments. The Romans were also big fans of the algae, using it to treat wounds, burns and rashes.
As were the Celts. It wasn't just East Asia that developed a taste for seaweed; it's been a cornerstone of traditional Irish and Scottish cooking for nearly 4000 years. Known as Dulse, a.k.a Irish moss, this red seaweed was most often eaten by monks and the indigent, which is why it has developed a strong stigma in both cultures as a food only fit for the most down and out — not unlike lobster.
Its ignominy as a foodstuff cemented in the last three centuries thanks to a series of governmental PR blunders — like the time it was famously fed to Scotland's poor when they were forcibly relocated from the highlands to coastal areas to make way for commercial sheep farming interests in the early 18th century and by starving Irish citizens during the 19th century potato famine. A second species, purple lavar (or "slake") is a key ingredient in Welsh lavabread and is greatly preferred to the third most common species, the green algae better known as sea lettuce.
Given seaweed's ability to harvest and concentrate a variety of valuable nutrients and minerals, they have often been used as traditional fertilisers the world over. In Scotland and Ireland, for example, nitrogen-rich and potassium-rich seaweed that washed up on shore would be collected, briefly composted, then dug into gardens as a fertiliser and soil conditioner to counter the region's thin, nutrient-poor soil.
Seaweed goes industrial
During the latter half of the 17th Century, seaweed made an important transition from product to precursor when Europeans — likely first in France and then spreading across the channel to the British Isles — discovered that burning seaweed produced an extremely alkaline ash consisting of soda and potash, two chemicals widely used in the day's glassware and glazing industries.
Soda ash — or as we know it sodium carbonate — is generally only derived from plants living in high-sodium soils like the Middle East while potash (potassium carbonate) is largely gathered from hardwoods. These chemicals are harvested by first collecting, drying, and burning plant matter. The ash is then dumped into a large open-top iron pot and soaked in hot water. The resulting alkali solution is then boiled and allowed to evaporate. The resulting white reside (hence "pot ash") was then collected and used in everything from glass-making to soap. Iodine can be extracted from seaweed in much the same way except that, after boiling, the alkaline solution is fixed through the addition of hydrogen peroxide which extracts the iodide ions rather than allowing the chemical to precipitate out like potash.
The bounty of seaweed along the British, Irish and Scottish coasts helped buoy the UK during its isolationist stint during the Napoleonic Wars when trade with Spain — which produced a similar product called Barilla ash (after the saltwort plant used in its production) — came to a halt.
By the start of the Industrial Revolution, iodine and alkaline extractions were old hat as the discovery of three molecules known as hydrocolloids — agar, alginate and carrageenan — proved to be of even more value. Derived from red and brown algae species (first accomplished in Japan, 1658 then again in the UK around the 19th century), these gooey, water-soluble molecules have the ability to thickening liquid — add just a little and you get a motor-oil consistency, add a bit more and its jiggle will put a bowl of jelly to shame.
By the 1930s these natural additives were widely used in industrial food and personal product production, from stabilising toothpaste (no more tooth powder, huzzah!) to inhibiting the formation of large ice crystals to keep ice cream's texture smooth. The commercial production of these algae species began just before WWII and really took off at the war's end. Today, some 55,000 tonnes of these three hydrocolloids are extracted from roughly a million tonnes of seaweed every year, a product worth $US585 million according to the FAO.
Agar is also widely used as a bacterial culture medium while sodium alginate is a ubiquitous part of the textile printing industry. What's more, the properties that make hydrocolloids so useful in gelling food products make them equally valuable in thickening a variety of other products found in the modern home — like soap, shampoo, lotions, skin creams and lube — that's right, many personal lubricants get their slide from carrageenan.
What's even more interesting is that this hydrocolloid appears to be a potent HPV inhibitor, according to this 2006 study by the National Cancer Institute, as it makes our cells too "slippery" for the virus to grab hold of.
Seaweed has made its way into more industrial arenas as well. The same process that allows seaweed to soak up nutrients makes it a viable method of extracting toxins from waste water — ammonia, ammonium, nitrate, nitrite, phosphate, iron and copper can all be extracted from water supplies through the power of seaweed's photosynthesis. [Drugs - Biomara - Seaweed - FAO - InTech - HuffPo - Wiki]