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How is seaweed harvested and used as a food, fertilizer, and industrial material?
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commercial fishing
Worker in the Tsukiji fish market, Tokyo.
Seaweed is harvested through both wild collection and aquaculture. Wild seaweed is often gathered by hand from intertidal rocks or collected after storms, while farmed speciesāsuch as Porphyra (nori)āare grown on nets or ropes suspended in marine environments and harvested by hand.12
Uses of Seaweed
- Food: Seaweed is a staple in many diets, particularly in East Asia and the Pacific. It is consumed directly as salads, in soups, or pressed into dried sheets. Additionally, phycocolloids extracted from seaweed, such as alginates, agars, and carrageenans, are widely used as thickeners and stabilizers in products like ice cream, puddings, and dressings.1
- Fertilizer: Seaweed has been used as an agricultural fertilizer for centuries. Farmers spread collected seaweed directly onto soil, or use commercial extracts that provide essential macronutrients and micronutrients to promote plant growth.13
- Industrial Material: Seaweed extracts are vital in manufacturing cosmetics, medicines, and shampoos. Historically, kelp was processed for soda, iodine, and potash, and during World War I, it was used to produce acetone for gunpowder. Experimentally, algae are also being explored as a sustainable source of energy.13