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SeaCell: The Ultimate Guide

Ideal for sensitive skin and hot summer months because it’s comfortable, cool, and breathable.

SeaCell is a lyocell fiber spun from two plants: seaweed harvested from the Icelandic fjords every 4 years, and wood pulp from Forest Stewardship Council certified eucalyptus and beech. It is made in a closed loop that recycles 99% of everything used. The result is a soft, breathable, machine-washable fiber that we knit into lightweight summer sweaters.

Kelp growing just below the surface of an Icelandic fjord, the seaweed that goes into SeaCell yarn

SeaCell, What’s So Special About It?

Soft

Gentle and lush on even the most sensitive skin.

Breathable

Keeps you cool on even the hottest summer days.

Sustainable

Completely biodegradable and recycles 99% of all waste.

Durable

Stronger and more durable than both cotton and linen.

Moisture-Wicking

SeaCell remains 85% dry in wet conditions.

Machine Washable

Doesn’t shrink, wrinkle, or need dry cleaning.

Seaweed churning under a breaking wave: it grows in the ocean without using arable land or fresh water
Kelp fronds close up: the marine plant that gives SeaCell its name and its lush, lightweight hand

Summer Sweaters Made From Seaweed

We made our new limited edition summer sweaters, the Big Sur, from seaweed... as in the stuff that grows in the ocean! Towering underwater like redwoods, seaweed grows vastly without exhausting arable land and fresh water. The material from these marine plants is ecologically sustainable and 50% more breathable than cotton.

We spent the last year perfecting a summer sweater, and a big part of our time was testing new material blends. In our long search, we kept coming back to a seaweed-based material called SeaCell. It’s arguably the most sustainable material on Earth. We’ve got you covered if you’re curious how we can create a clothing material from seaweed. We answer all of your questions in this guide, and before you know it, you’ll understand why we choose SeaCell for our line of summer sweaters.

What Is SeaCell?

Technically speaking, SeaCell is a type of Lyocell, which we’ll get into a bit later in this guide, but generally, Lyocell has 2 defining characteristics:

  • It’s made by reconstructing cellulose (plant cells) and then spinning it into fibers that can be blended with other materials like cotton and wool or spun on its own into yarn.
  • It’s made in a “closed-loop.” Closed-loop means that the production process does not release solvents into the environment, unlike viscose. An organic solvent is used throughout the entire closed-loop process, and the Forest Stewardship Council has recognized the solvent as non-toxic.

SeaCell combines two different plant fibers, seaweed (obviously) and wood pulp harvested from eucalyptus tree farms.

An Icelandic harvesting vessel trimming only the tops of a seaweed bed, which is what lets the bed regrow
Knotted Wrack seaweed floating at the surface of a cold Icelandic fjord, the plant SeaCell is named for

Where Does SeaCell Come From?

Seaweed is harvested from the cool blue waters of Iceland every 4 years. Similar to how yaks graze, we only take the tops of the plant, leaving the lower sections to regenerate. The wood pulp comes from Eucalyptus and Beech Trees, two fast-growing trees that require little water. These trees are harvested in Europe from Forest Stewardship Council (FSC) certified tree farms. The FSC certification means that a newly planted tree must replace every tree used in the production of SeaCell. The resulting combination is a durable, silky, breathable fiber that’s gentle on sensitive skin.

Wood Pulp, Lyocell Explained

You’re thinking, what the heck! You said seaweed; now I’m to understand that’s there’s wood pulp in here? So what is it, seaweed or wood? The short answer is it’s both. We call it SeaCell and not WoodCell because the fiber’s magic comes from seaweed. It’s the secret ingredient for summer sweaters. While theoretically, we could make a Lyocell fiber using 100% seaweed, it’s not practical or as environmentally friendly.

The two materials, seaweed and wood, are better when they work together. Wood is denser than seaweed, which means that a bit of wood goes a long way, so we can use fewer resources to make more sweaters. Seaweed fibers are famously lush, skin-friendly, and lightweight, perfect for a summer sweater. Additionally, seaweed grows abundantly without needing fresh water or arable land. By blending seaweed into wood-based lyocell, we’ve made a sustainable fiber even more Earth-friendly. These two fibers are Simon and Garfunkel. Individually they are good, but when they work together, they have a profound gift of harmony.

Looking up through a eucalyptus plantation, a fast-growing hardwood that needs a tenth of the water of an average tree

Is Lyocell Eco-Friendly?

In making SeaCell, we use a combination of eucalyptus and beech wood certified by the Forest Stewardship Council (FSC). We use these two species because they are sustainable hardwoods that grow abundantly worldwide in many different climates. They also grow on land that otherwise wouldn’t be used for food production. These trees also require a minimal amount of water compared to other plants. Eucalyptus, in particular, is remarkably water-efficient, requiring 1/10 of the water of the average tree to grow. Also, eucalyptus is fast-growing, making it a highly regenerative resource and one of the most sustainable materials in the yarn world. The fiber yield per acre from eucalyptus is 10x higher than cotton.

How Is SeaCell Made?

Let’s dig into how we get from seaweed and wood to a fiber ideal for our lightweight summer sweaters. The first step is turning wood into fiber using a process known as NMMO or closed-loop technology. Then, within the closed-loop, we create SeaCell while reusing the solvents. The NMMO transforms the wood into a liquid pulp. To make SeaCell, ground seaweed is blended like a cake batter. Then, we take this “batter” and force it through tiny holes called spinnerets to create long thin fibers that we spin into yarns. Fun fact: a spinneret machine is a mechanical copy of a spider’s silk-spinning organ.

  • Step 1: seaweed growing underwater in a clear Icelandic fjord, with small fish among the fronds
  • Step 2: the harvested seaweed dried into dark green flakes
  • Step 3: the dried seaweed milled into a fine pale green powder
  • Step 4: the other raw material, a Forest Stewardship Council certified eucalyptus plantation
  • Step 5: eucalyptus and beech cut into wood chips ready for the closed loop
  • Step 6: the wood chips dissolved into soft white cellulose pulp
  • Step 7: the pulp forced through the spinnerets and drawn out into long fine white filaments
  • Step 8: the finished SeaCell fiber, soft and pale, ready to be spun into yarn and knitted

How Is The Seaweed Harvested?

The seaweed used to make SeaCell is technically an algae called Ascophyllum nodosum, also known as Knotted Wrack, a strain of seaweed found in the Icelandic fjords and northern Atlantic. Harvesting in the Icelandic fjords means there is no pollution and waste from ship traffic, so the seaweed is extremely clean and without pollutants. Local Icelandic sea farmers gently harvest the abundant seaweed beds once every 4 years using large floating conveyor belts that remove the tops of the plants. The harvesting process ensures that each bed can naturally regenerate without disrupting the ecosystem. Solely trimming the upper portion of the marine plant also encourages healthy growth, like cutting the split ends of our hair. Once cut in Iceland, it’s transported to manufacturing facilities in Austria. The seaweed is entirely untreated, retaining all its natural properties.

A SeaCell crew neck worn outdoors: smooth fibers next to the skin, an open knit for heat, and machine washable

What Are SeaCell’s Properties And Benefits?

We only use high utility sustainable materials. While khullu is the undefeated champ of wools, SeaCell is the best plant-based material.

How much more breathable SeaCell is than cotton
50%
The water it needs compared with cotton
<1%
How long each Icelandic seaweed bed regrows before it is cut
4 years
The water and solvent recovered every time the fiber is spun
99%
  • Anti-Irritant: SeaCell fibers are smooth, unlike wool and cotton. The silky fibers don’t irritate sensitive skin. SeaCell is efficient at moving sweat and moisture away from your body, discouraging bacteria growth that causes skin irritation.
  • Breathability: Seaweed aside, Lyocell fiber also has some remarkable properties that make it perfect for a summer sweater. For example, compared to cotton, Lyocell is 50% more breathable.
  • Moisture-Wicking: SeaCell fibers retain 85% of their dry tenacity in wet conditions... this means that SeaCell moves moisture away from your body and into the air keeping you cool in the heat.
  • Protection: The fibers effectively catch free radicals, which we are exposed to daily and can damage our skin cells. It’s hard to find a more soothing material to wear directly on your skin than SeaCell, protecting against the sun with a UPF 50+ rating that comes from how tightly we knit it.
  • Durability: SeaCell is durable; even the most durable synthetic fibers are only 20% stronger than SeaCell. SeaCell is also 2x stronger than cotton and viscose while dry and 3x stronger while wet. Being strong while wet exhibits how you can machine wash it many times over the years while retaining the shape of your go-to sweater.

How Does SeaCell Compare To Others?

How does SeaCell stack up against other materials such as yak wool, cotton, viscose, and other synthetics?

SeaCell compared with yak wool, cotton, viscose and polyester on five properties, as published in the Oliver Charles SeaCell guide
Property SeaCell Yak Wool Cotton Viscose Polyester
Anti-Irritant Yes No Yes No No
Breathability Yes Yes Yes No No
Sustainability Yes Yes Yes No No
Durability Yes Yes Yes Yes Yes
Moisture-Wicking Yes Yes No No No
  • SeaCell Vs Lyocell: SeaCell is a type of lyocell. All Lyocell fibers are made through closed-loop production from natural cellulose (plant) fiber. SeaCell comes from both seaweed and wood cellulose.
  • SeaCell Vs Yak Wool: SeaCell and yak wool are different. One comes from an animal, and the other comes from plants. In direct comparison, yak wool is about 2x more breathable than SeaCell. Yak wool is also higher performing in keeping odors at bay. The crimps in yak wool provide greater insulation and warmth as well. Yak wool is the undisputed champion of wool fibers (and, therefore, all materials). However, SeaCell is the undisputed champion of plant fibers, providing the best sustainable wool alternative. In addition to performing at the top of its plant fiber peers (cotton, viscose, linen, hemp), SeaCell is a better option than yak wool for sensitive skin.
  • SeaCell Vs Cotton: SeaCell requires less than 1% of the amount of water as cotton. Organic cotton is primarily watered by rain and is closer to SeaCell in water consumption. However, only about 1% of all cotton grown is done so organically. SeaCell is also 2x stronger than cotton while softer due to its silky-smooth fibers.
  • SeaCell Vs Viscose: SeaCell is 2x stronger and more sustainable than viscose. Viscose is not sustainable in clothing due to its toxic and wasteful production method. Viscose factories emit nearly 90,000lbs of carbon disulfide into the air, which is poisonous. Also, 50% of the world’s viscose production comes from threatened forests, and 70% of the wood used in viscose production is dumped or incinerated due to inefficiency. SeaCell, alternatively, uses non-toxic solvents and recycles 99% of everything used in manufacturing.
  • SeaCell Vs Polyester: SeaCell is in a different league than any plastic-based synthetic. SeaCell is more breathable, has better moisture management, and doesn’t depend on fossil fuels for production. Beyond performance benefits, SeaCell is 100% biodegradable, unlike synthetics. Every time you wash a synthetic article of clothing, it loses up to 2,000 non-biodegradable microplastic fibers, eventually ending up virtually anywhere on the planet.

How much moisture each fiber can pull off your skin

The share of its own dry weight the fiber itself absorbs as water vapor, then releases into the air.

  • SeaCell 12%
  • Cotton 8.5%
  • Polyester 0.4%
A fiber that can hold and release moisture is a fiber that feels dry against the skin. Polyester holds almost none, which is why a synthetic top feels clammy in the heat and a SeaCell sweater does not.

SeaCell’s lyocell base can hold around 12% of its own weight as moisture and give it back to the air, cotton about 8.5%, and polyester almost none at 0.4%. That is roughly a thirty-fold gap between SeaCell and polyester in how much sweat the fiber itself can take off your skin, which is what you feel as cool and dry.

A single kelp frond lit from above in clear water: a regenerative crop that grows back without land, irrigation or plastic

How Sustainable Is SeaCell?

Even sustainable brands can’t break their addiction to plastic-based synthetic fibers. Companies are tempted to make clothes from synthetic fibers because they are soft, strong, and globally abundant. But plastic-based synthetic fibers are massive polluters through their manufacturing and leaching non-biodegradable microplastics into the world. We can replace plastic-based synthetic fibers with SeaCell! It’s soft, abundant, and strong. However, unlike plastic polyester, SeaCell is made from regenerative resources and 100% biodegradable.

SeaCell compared with organic cotton, viscose and polyester on four sustainability attributes, as published in the Oliver Charles SeaCell guide
Attribute SeaCell Organic Cotton Viscose Polyester
Natural Fiber Yes Yes Yes No
Organic Yes Yes No No
Biodegradable Yes Yes Yes No
Resource Efficient Yes Yes No No

Seaweed grows abundantly in its natural saltwater ocean habitat. Eucalyptus proliferates without irrigation or pesticides and can be grown on extremely dry land. Both ingredients, seaweed and eucalyptus, use renewable energy in their production processes, and neither raw material needs additional fresh water to grow. The Lyocell production process used to make SeaCell conserves 99.5% of all waste and water in a closed-loop system that doesn’t leak toxic chemicals into the environment or require additional fresh water.

The Big Sur coastline the summer sweater is named after, the kind of warm day a SeaCell knit is made for

World’s Most Sustainable Material

SeaCell has earned over 16 environmental certifications. These are the ones we name, and each one can be checked by name with the body that issues it.

  • OEKO-Tex Standard 100 mark: SeaCell is tested to contain no harmful substances OEKO-Tex Standard 100

    SeaCell is tested not to contain any harmful substances. The strict requirements of this certification go beyond US and international standards.

  • Forest Stewardship Council mark: a tree is planted for every tree used to make SeaCell Forest Stewardship Council

    The FSC ensures that companies responsibly manage forests. They help prevent over-harvesting by requiring that a tree be planted for every cut.

  • USDA Biobased mark: SeaCell is made from renewable plant material rather than petroleum USDA Biobased

    SeaCell is certified as biobased and derived from renewable materials. Biobased products displace 300M gallons of petroleum per year in the US.

  • Vincotte composting mark: SeaCell breaks down in composting rather than persisting as microplastic Vincotte Composting

    Guarantees biodegradability. SeaCell is certified as compostable in both higher temperature industrial facilities and lower temperature home gardens.

  • Organic certification mark covering the seaweed harvested in the Icelandic fjords Certified Organic

    Certification of sustainable practices in agriculture, in the case of SeaCell the sustainable harvesting of seaweed in the cold waters of Icelandic fjords.

  • EU Ecolabel mark covering the full production lifecycle of the SeaCell fiber EU Ecolabel

    Label of environmentally friendly goods, awarded to SeaCell for meeting high standards for sustainability throughout its entire production lifecycle.

  • Intertek eco-certification mark held by the producer of SeaCell fiber Intertek Eco-Certification

    Certificate of quality assurance on incoming materials, ensuring no harmful substances are introduced through the production lifecycle.

Why SeaCell Is Perfect For Summer Sweaters

It should be pretty obvious by now as to why we decided to use SeaCell in our summer sweaters. But, just in case, let’s go through and check the boxes, starting with the most important...

  • Is SeaCell Sustainable? YES! It’s hugely sustainable every step of the way, from the collection of the raw materials to manufacturing fibers; SeaCell is arguably the world’s most sustainable yarn.
  • Is SeaCell Breathable? SeaCell is naturally moisture-wicking, keeping you cool on even the hottest summer days.
  • Is SeaCell Irritating On Skin? No! In fact, it’s one of the softest, most skin-friendly materials out there!

Additionally, our new summer sweaters are 3D-knit using an extremely fine gauge, meaning they are light as a feather.

Sweaters are not the only thing we knit from it. Our SeaCell t-shirt, made in America, has a post of its own.

SeaCell FAQ

Are Your Sweaters 100% SeaCell?

No, we use a blend of SeaCell and organic cotton. SeaCell yarn is extremely fine, making it ideal for blending with other plant fibers for comfort.

Is SeaCell Machine-Washable?

Yes, SeaCell is machine washable and will not shrink on a normal cycle.

Why Isn’t SeaCell More Popular?

It’s still a “rare” fiber; we can only harvest the seaweed once every 4 years, meaning production will take a while to catch up with demand, which is a good thing! That’s the whole point of the slow fashion movement.

Where Is SeaCell Made?

Smartfiber produces SeaCell in Austria in the Lenzing AG facilities. Lenzing AG is the inventor of the Lyocell process and the leading fiber producer (they make TENCEL).

Does SeaCell Use Toxic Chemicals?

The seaweed-based yarn we use is more sustainable than viscose rayon. Seaweed is turned into SeaCell with a Forest Stewardship Council-recognized organic, non-toxic solvent and recycles 99% of everything used in manufacturing. Unlike SeaCell, viscose rayon has a toxic and wasteful production method.

Viscose rayon factories emit nearly 90,000lbs of carbon disulfide into the air, which is poisonous. Also, 50% of the world’s viscose production comes from threatened forests, and 70% of the wood used in viscose production is dumped or incinerated due to inefficiency.

Is SeaCell Sustainably Harvested?

The seaweed used to make SeaCell comes from Icelandic fjords, where there is no pollution and waste from ship traffic. Local Icelandic sea farmers gently harvest the abundant seaweed beds once every 4 years using large floating conveyor belts that remove only the very tops of the plants and do not cast nets that capture faunae. The harvesting process ensures that each bed can naturally regenerate without disrupting the ecosystem. Solely trimming the upper portion of the marine plant also encourages healthy growth, like cutting the split ends of our hair.

Is SeaCell Economically Sustainable?

Harvesting seaweed is economically sustainable for farmers. Growing seaweed does not require expensive pesticides or dwindling farmland, making it inexpensive to grow. However, seaweed has quickly increased in demand over the last several years for use in products such as clothing, food, and fertilizer creating a profitable market for farmers selling the commodity.

Stop wearing plastic. Oliver Charles knits summer sweaters from seaweed.

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