The best place to start with a new material is often the trash can. For Julia Marsh, the Californian designer behind Sway, the starting point was the polybag, the thin, crinkly plastic sleeve that protects a new shirt or a pair of shoes on its journey from factory to closet. It is a single-use item designed to last centuries, and it is everywhere. Marsh, inspired by a lifelong affection for the ocean, wondered what would happen if you made it from seaweed instead, and designed it to disappear in a backyard compost pile [Prime Brown University, undated] [The Helm, undated].
Sway, founded in 2020 and based in Oakland/Berkeley, is betting that the answer is a viable business. The company has developed a line of home-compostable packaging films derived from seaweed, aiming to match the performance of conventional plastic while slotting into existing manufacturing equipment [F6S, undated] [Designer Fund, 2023]. It is a classic climate tech wedge: find a ubiquitous, problematic product, and replace it with something that performs the same job without the eternal environmental cost. The ambition is not to reinvent the packaging line, but to feed it a different feedstock.
The Regressive Resource
The core of Sway's pitch is the resource itself. Seaweed grows quickly, requires no freshwater, fertilizer, or arable land, and actively sequesters carbon while improving ocean health [Parley, undated]. It is, in the startup's framing, a regenerative input rather than an extractive one. This is the foundational unit economics of their climate claim. If you are going to make billions of flexible films, you need a feedstock that scales without competing with food crops or adding to deforestation.
Sway's technical challenge has been to turn that seaweed into a thermoplastic resin that behaves like the plastic brands and manufacturers already know. The company says it has developed a patented seaweed-based biopolymer that works as a drop-in solution within traditional plastic infrastructure [The Helm, undated]. Their first commercial product is a home-compostable polybag, printed with ink derived from algae. Sway's February 2024 press release names J.Crew, Burton, and others as brand partners. Crunchbase additionally lists Dr. Bronner's and Faherty as customers [Author note, May 2026]. The target customer is any brand or retailer looking for a regenerative alternative to plastic waste, particularly in sectors like fashion and beauty where packaging is both essential and a reputational liability [F6S, undated].
Validation Before Volume
For a pre-revenue materials startup, credibility is currency. Sway has been aggressive in collecting it, not through disclosed sales figures, but through awards and high-profile recognition. This is the startup's traction signal in lieu of shipment tonnage.
- Prize money. The company was a winner of the Tom Ford Plastic Innovation Prize in 2023, receiving $600,000, which included a direct equity investment from Trousdale Ventures [Packaging World, undated] [Author note, May 2026].
- Industry challenge. It previously won the Beyond the Bag Challenge run by the Closed Loop Partners consortium in 2021 [F6S, undated].
- Media landmark. In late 2024, Sway and founder Julia Marsh were profiled in Oprah Daily, a signal of mainstream cultural reach [Oprah Daily, Oct 2024].
- Invention list. Most recently, Sway Seaweed Packaging was named one of TIME's Best Inventions of 2025 [Sway TIME, 2025].
This track record has helped attract an estimated $7.5 million in total funding from a mix of impact and venture investors, including Valor Siren Ventures, Alante Capital, BAM Ventures, The Helm, and Third Nature [Sway Funding, undated] [Author note, May 2026].
The Team's Creative Bent
The founding team reflects the product's origin at the intersection of design, brand strategy, and environmental science. CEO Julia Marsh is a designer focused on scaling regenerative technology with consumer brands [PatSnap, undated]. Her life and business partner, Matt Mayes, serves as COO, with a career centered on improving sustainability practices within large organizations [The Org, undated]. Leland Maschmeyer, an early creative contributor, is the Chief Creative & Strategy Officer at Chobani, bringing a deep understanding of how major brands build narrative and consumer trust [PatSnap, undated] [TechCrunch, 2020]. This is not a team of PhD polymer scientists; it is a team built to translate a material innovation into a brand proposition.
| Founder | Role | Background |
|---|---|---|
| Julia Marsh | CEO & Co-Founder | Designer, scaling regenerative tech with brands. |
| Matt Mayes | COO & Co-Founder | Sustainability operations for large organizations. |
The Scaling Equation
The road from a prize-winning prototype to a commodity-scale material is long, expensive, and littered with the skeletons of promising bioplastics. Sway's most immediate challenge is proving it can manufacture consistently, at volume, and at a cost that brands can swallow. The company has not disclosed any production capacity figures or per-unit pricing. The other looming question is the actual end-of-life performance of "home-compostable" in a world of variable backyard compost piles. Industrial composting standards are one thing; convincing a consumer that a bag will break down in their bin is another.
They are also not alone in the seaweed packaging arena. Competitors like Notpla (UK-based, focused on rigid and flexible coatings) and Loliware (US-based, making seaweed-based straws and cups) are chasing similar markets with different product forms [Private candid take]. Sway's bet is that its focus on thin films for fashion and its drop-in manufacturing compatibility will carve out a specific and valuable niche.
Back of the envelope: The global polybag market is vast, but consider just the fashion sector. If Sway could replace the polybags for, say, 10 million garment shipments annually, and their material carries even a modest premium, the revenue potential quickly enters the tens of millions. The real calculation, however, is in carbon and plastic waste avoided. Replacing a fossil-derived polyethylene bag that persists for 500 years with a seaweed-based film that composts in months changes the entire lifecycle math of a shipped product.
For Sway to succeed, it must ultimately beat the incumbent not on feel-good branding, but on cold, hard unit economics. It must become the polybag that works just as well, doesn't cost too much more, and lets everyone,from the brand to the end customer,feel a little better about the transaction. The early validation suggests they have the story. The next twelve months will be about proving they have the supply chain.
Sources
- [F6S, undated] Sway company profile | https://www.f6s.com/company/swayinnovation
- [Designer Fund, 2023] How Sway is Turning Seaweed Into Plastic | https://designerfund.com/blog/sway-julia-marsh-interview
- [Oprah Daily, Oct 2024] Seaweed-Based, Home-Compostable Packaging Is Here: Meet Sway | https://www.oprahdaily.com/life/a70226222/julia-marsh-sway-startup/
- [Parley, undated] Material Revolution: Sway Seaweed Plastic | https://parley.tv/journal/material-revolution-sway-seaweed-plastic
- [Prime Brown University, undated] Julia Marsh profile | https://prime.brown.edu
- [The Helm, undated] Sway company profile | https://thehelm.co
- [Packaging Dive, undated] Sway develops seaweed-based polybags | https://www.packagingdive.com
- [Packaging World, undated] Tom Ford Plastic Innovation Prize winners | https://www.packagingworld.com
- [Sway TIME, 2025] Sway Seaweed Packaging Named TIME Best Invention of 2025 | https://swaythefuture.com/press-release-time
- [Sway Funding, undated] Sway Unveils New Tech, Closes on $5M in Funding | https://swaythefuture.com/sway-unveils-new-tech-closes-on-5m-funding
- [PatSnap, undated] Sway company discovery profile | https://discovery.patsnap.com/company/sway/
- [The Org, undated] Matt Mayes profile | https://theorg.com
- [TechCrunch, 2020] River, the latest venture from Wander founder Jeremy Fisher, launches | https://techcrunch.com/2020/10/15/river-the-latest-venture-from-wander-founder-jeremy-fisher-launches-with-10-4-million-in-funding/