The Other Uses of Seaweed: Medicine, Farming, Materials and Three Centuries of a Scottish Shore

By Jayson Byles, forager & chef · September 2026

Seaweed is used for far more than food. It dresses wounds and thickens medicines, feeds crops and cattle, goes into supplements and skincare, sets puddings and grows the bacteria in every hospital laboratory, and is now being turned into packaging, textiles, battery parts and building insulation. Most of that starts with the same few compounds, made by the same few families of seaweed, several of which grow on the shore where we run our workshops. This is a plain, sourced guide to those other uses, from the kelp fires of the seventeenth-century Forth to the trials and start-ups of 2026, with a page of its own on each.

We write it as harvesters. East Neuk Seaweed cuts wild seaweed by hand on the East Neuk shore, between Elie and Kingsbarns, for our own kitchen, for chefs, and increasingly for people who need an identified Scottish species in modest, traceable quantities: a named plant from a named shore, cut on a known date. That last sentence turns out to be what most of these industries need first, and it is the thread through everything below.

The nine uses, at a glance

Three hundred years in one table

Where it all started: the kelp shore

The first industrial use of Scottish seaweed was as ash. Burnt in stone-lined pits on the shore, dried wrack and kelp gave a crude alkali for glass and soap, and later the raw material for iodine. The earliest Scottish records are on the Forth, where the Leith glassworks was buying kelp by 1664; organised burning is usually said to have begun in Fife in the 1690s, moved to Orkney in the 1720s and the Hebrides in the 1740s, and at its height put tens of thousands of people to work on the shore each summer. Its collapse in the 1820s, when cheaper alkali arrived from Spain and from the new chemical works, left communities that had been settled on the coast to gather weed with nothing to gather it for, and it is one of the forces behind the Clearances. The shore we cut today carries that history in its place names and in the ruined kelp kilns you can still find above the tideline. The full story, with the Forth and Fife beginnings that few histories mention, is on the history of seaweed in Scotland page.

Food first: what seaweed does for the people who eat it

Everything else on this page is downstream of the fact that seaweed is nutritious. A portion of dulse gives protein, iron, calcium and vitamins A to D; the kelps give fibre, potassium and a great deal of iodine; the greens give folate and a little of everything. Iodine is the point to understand. Adults need about 140 micrograms a day, according to the NHS, and it is the one seaweed nutrient with authorised health claims attached: it contributes to normal thyroid function, normal cognitive function and normal energy-yielding metabolism. Brown seaweeds can also deliver far more than that in a single serving, which is why kelp is a seasoning in our kitchen rather than a vegetable, and why the reds and greens can be eaten more freely. The benefits and nutrition page sets out the numbers portion by portion, and our guide to cooking seaweed puts them to use.

Supplements: the capsule end of the market

Kelp tablets, bladderwrack capsules and fucoidan supplements sell on the strength of the same iodine and polysaccharides, and the honest summary is that the label is the weak point. A 2023 University of Glasgow survey of UK seaweed products found the median single serving carried more than 400 micrograms of iodine and that some supplements exceeded the tolerable upper level; a separate analysis found the iodine declared on kelp supplements was unreliable for most products. We do not sell supplements. We sell the whole plant, and the supplements page explains what to look for on a label if you buy one, what the NHS says about safe amounts, and why the whole food is easier to judge.

Nutraceuticals: the compounds behind the claims

Behind the supplement shelf is a small chemistry. Fucoidan, a sulphated polysaccharide found only in brown seaweeds; fucoxanthin, the pigment that makes them brown; phlorotannins, the polyphenols that give the wracks their taste; alginate and laminarin, the kelps' structural and storage sugars. All are well characterised in the laboratory and heavily studied in animals, and the human trials are still small: a 2025 trial of fucoidan with resistance training, a UK gut-health study reporting in 2025, a Mayo Clinic fucoidan trial due in 2027. In Great Britain fucoidan extracts are authorised as novel foods only from two species and only up to 250 milligrams a day, and none of these compounds has an authorised health claim. The nutraceuticals page maps each compound to the species we cut, grades the evidence, and sets out the claims and novel-food rules for anyone formulating with them.

Medicine: the seaweed you have already taken

If you have ever taken a raft antacid for heartburn, the raft was sodium alginate from brown seaweed. If you have had a leg ulcer or a surgical wound dressed, the dressing may well have been calcium alginate fibre, in clinical use since the early 1980s and standard on NHS formularies. Carrageenan and agar carry and set drugs; agar is the jelly in every culture plate. These are the established uses, and the argument in that world is about grade and supply, not evidence. The research end is livelier: fucoidans that blocked SARS-CoV-2 in cell culture in 2024, carrageenan nasal sprays in human trials, fucoidan microneedles delivering an anticoagulant through skin in animals. The seaweed in medicine page tells the story from Courtois's violet vapour to the trials now running, and draws the line between the two plainly.

Skincare and cosmetics

Seaweed has been rubbed on skin for as long as it has been eaten, and around 1900 there were some 300 seaweed bath houses in Ireland alone. Today phlorotannins, fucoidan, ulvan and the sunscreen-like amino acids that red seaweeds make for themselves all appear in cosmetic formulations, and two Scottish brands built on Hebridean seaweed have made the clean northern shore an ingredient in its own right. The clinical evidence is real but modest: moisturising and anti-pigmentation effects in small studies, long-term data lacking. The skincare and cosmetics page reviews what the studies show, names the compounds and the brands, and explains how to run a seaweed bath at home with a bag of fresh bladderwrack.

The garden and the farm

The oldest use of all is on the land. Crofters built their lazy beds with seaweed for manure, and cast weed from the strandline is still one of the better things you can put on a Fife vegetable bed: potassium, trace elements, and growth-promoting compounds that the biostimulant industry now extracts and bottles. The James Hutton Institute in Dundee is testing sugar-kelp extracts that help crops take up nutrients when fertiliser is short; WWF-UK and Cefas have been measuring the footprint of seaweed biostimulants. On the livestock side, a red seaweed called Asparagopsis cut methane from grazing beef cattle by around 38 per cent in a 2024 trial, with a bromoform safety question still being worked through by regulators, and Queen's University Belfast has found native UK seaweeds that manage a smaller cut without it. The garden page covers how to use seaweed at home and the law on collecting it; the farm page covers crops, soil, feed and the Scottish policy behind it.

Materials and the future: packaging, batteries, textiles, carbon

The newest uses are the ones that make headlines. Notpla's seaweed-coated boxes and edible drink capsules had replaced 21 million single-use plastic items across Europe by June 2025. Researchers at Bristol built a battery separator from seaweed nanocellulose; Marine Biopolymers in Ayr and the University of Glasgow made alginate binders that lengthen the life of silicon anodes; a 2026 paper reports an alginate binder holding 94 per cent of capacity in a sodium-ion anode. Kelp yarn walked the Stella McCartney runway. Seaweed farms are being measured for the carbon they draw down. The seaweed materials page covers both halves: the chemistry underneath, from hydrogels and bioprinting inks to seaweed-derived carbon, and a kept-current account of which packaging, battery, textile and carbon stories are on sale, in pilot or still in the laboratory.

Why a single Scottish shore matters

Read across those nine pages and one requirement repeats. The supplement maker needs to know the iodine in the batch. The pharmaceutical formulator needs a defined species with a certificate of analysis. The skincare brand wants a named northern shore on the label. The researcher needs ten kilograms of one plant, cut on a known date, three times a season. None of them is served by a mixed bale of unidentified weed, and all of them are served by what a small hand-harvester does as a matter of course. We cut above the growing point on a rotation and never pull, so the bed is there next year; we harvest under the licence rules explained in our guide to the law; and the same shore feeds our workshops, where you can stand on it and see the plants for yourself. Scotland's case in this industry, against France and Portugal, is clean water, cool seas and identity, and the Scottish Government's own sector study models bioactives as its fastest-growing part. A single source on a single shore is not a limitation. It is the product.

Sources

Each spoke page carries its own full source list. The figures quoted directly on this page come from:

• Sifting through the remains of Scotland's kelping industry (The Past)
• History of Scottish seaweed (Scottish Seaweed Industry Association)
• Bernard Courtois and the discovery of iodine (Britannica)
• Seaweed at SAMS in wartime and today (Scottish Association for Marine Science)
• Kathleen Drew-Baker, Mother of the Sea (Science and Industry Museum)
• Iodine (NHS)
• Great Britain nutrition and health claims register
• Seaweed products on the UK market and their iodine content (British Food Journal, 2023)
• Novel food authorisation: fucoidan extracts (Food Standards Agency)
• Fucoidan for chemotherapy-related fatigue, Mayo Clinic trial (ClinicalTrials.gov)
• Alginate dressings: a history (Journal of Tissue Viability, 1997)
• Fucoidans and rhamnan sulfates against SARS-CoV-2 (2024)
• Irish seaweed bath houses (Voya)
• Seaweed to improve crop fertiliser use (James Hutton Institute)
• Asparagopsis and methane in grazing beef cattle (PNAS, 2024)
• Native seaweeds and methane (Queen's University Belfast)
• Oceanium biorefinery and fucoidan launch (2024)
• Seaweed is taking plastic out of stadiums and sandwich boxes (Euronews, June 2025)
• Seaweed-based battery separator (University of Bristol)
• Scottish seaweed alginate binders for EV batteries (Envirotec, 2023)
• Cross-linked alginate binder for sodium-ion anodes (Advanced Functional Materials, 2026)
• UK Seaweed Network launched (UCL, 2026)
• Understanding the potential scale for seaweed-based industries in Scotland (Scottish Government, 2022)

Questions we get asked

What is seaweed used for besides food?

Medicine (alginate wound dressings, raft antacids, carrageenan and agar as excipients, agar culture plates), supplements and nutraceuticals, skincare, garden fertiliser and farm biostimulants, methane-reducing cattle feed, and a growing list of materials: packaging, textiles, battery components, insulation and bioinks. Iodine itself was first extracted from seaweed ash.

What products contain seaweed?

Raft antacids such as Gaviscon (sodium alginate), alginate wound dressings, many ice creams, plant milks and toothpastes (carrageenan and alginate), culture plates in laboratories (agar), liquid garden feeds, kelp and bladderwrack supplements, a wide range of skincare, and seaweed-coated food packaging. Most use extracted compounds rather than the whole plant.

Why was seaweed so important in Scottish history?

From the 1690s to the 1820s burnt seaweed, or kelp, was Scotland's source of industrial alkali for glass and soap, and later of iodine. Tens of thousands of people worked the shores each summer, and the trade's collapse when cheaper alkali arrived helped drive the Clearances. Its earliest records are on the Forth, and it is usually said to have begun in Fife.

Which seaweed compounds are used in industry?

Alginate from kelps and wracks, carrageenan from carrageen and its relatives, and agar from other red seaweeds are the three hydrocolloids that underpin the food, pharmaceutical and materials uses. Fucoidan, fucoxanthin, phlorotannins and laminarin from brown seaweeds are the compounds behind the supplement and nutraceutical trade.

Can I buy Scottish seaweed as a raw material?

Yes. We supply identified, hand-cut species from the Fife shore, fresh in 5 kg lots or dried in small bespoke batches, with the species, shore and harvest date recorded and testing available on request, to kitchens, producers, makers and researchers across the UK.

This guide describes how seaweed is used and studied. It is not medical, nutritional or regulatory advice; each spoke page carries the specific caveats for its subject.