Seaweed, shrimp & bioplastics

Also: reflections on 5 years of seaweed reporting

It was at the end of 2024 I felt I finally had a grasp of how seaweed markets function. A long-awaited visit to Tawi-Tawi, the birthplace of tropical seaweed aquaculture, capped off a five-year journey.

I condensed my findings in a series of articles and talks. For tropicals, I wrote about the markets for carrageenan and sea moss, and for cold waters, a broad overview of current markets and possible futures for temperate species for a Springer book on temperate phyconomy (to be published later this year).

I had moved a stone in the river, and thus delivered proof of my existence. But what was I supposed to do next? Of course, there is always more to say, new developments to cover. But at the same time, the questions that loomed large in 2020 have, to a large degree, been answered.

The potential for seaweeds as a climate change solution is now considered to be mainly in mitigation, not sequestration. The contours of the markets for seaweed-based agri-inputs became increasingly well defined over the past few years, while biomaterials and other new applications showed themselves to be much further away from mainstream adoption than was hoped, regardless if made from seaweeds or other biomass. Meanwhile, keeping track of developments on the cultivation side is a bit like watching grass grow.

The dearth of news had already led my fellow seaweed reporters to pivot. The Paxtier Report went on hiatus in August as Peter Green turned to blue carbon, while Fed Degobbi’s seaweed podcast rebranded to The Ocean Age.

Seaweeds attach, seaweeds drift. Time to trade in my terrestrial obsession for fixity and assuredness for the fluctuating rhythms of what Kamau Brathwaite called a tidalectic world view? With no answers forthcoming, I entered a pelagic phase.

From shrimp…

Bạc Liêu, in Vietnam’s Mekong Delta, is shrimp country - but will it remain so? At the moment, it’s GIGO (garbage in, garbage out). While the industry is not on a clear path to collapse, it is in dire need of significant improvements in sustainability if it wants to avoid continued instability and long-term contraction.

I saw some different takes on the problem: Dragos from Good Tom tries to apply science-backed management practices to revive collapsed shrimp farms, while Nick from Halophilic Marine Agriculture grows samphire in ponds already abandoned. CK at Rongbient wants to co-culture Gracilaria and shrimp, and then feed it back to the shrimp as a feed supplement.

Growing seaweeds and shrimp together is nothing new and the science is clear: it helps with water quality and disease, and both shrimp and seaweeds productivity shoot up, boosting profits massively. Add in milkfish and productivity increases even more.

In Indonesia, where polyculture is quite common already, adoption could be increased by a focus on the least educated farmers, who are the least likely to embrace new ideas. In other countries, there is little point in growing more seaweeds without first finding buyers for the crop.

Processing the seaweeds into a shrimp feed supplement is one idea to create a new market in a place like Vietnam. Once again, the science is pretty clear: it works, more shrimp survive. But a chance encounter with a hydrolysate producer in Saigon made me understand the challenge companies developing seaweed shrimp feed supplements face.

First off, the feed mills who you need to include your supplement in their formulation will take some convincing: years of field trials and relationship building await. Secondly, similar to biostimulants, there is a huge range of options for the feed mills to choose from: prebiotics, probiotics, synbiotics, enzymes, organic acids, amino acids, fatty acids, hydrolysates, yeast extracts, squid liver powder, … the list goes on. A lot of competition.

So I wasn’t completely taken aback when I bumped into Nelson from Sea6 Energy at Seagriculture in Australia and he told me they had paused development on their shrimp supplement product despite positive trial results. “We walked that long road once before with our biostimulant product - we didn’t feel like doing it all over again. We decided to focus instead on our bioplastics range.”

…to bioplastics…

What kind of bioplastics, Nelson? “Well, coatings is something we’re working on.”

Glad you mentioned it. While Searo, Plantsea, Flexsea, B’Zeos, Sway and others have a variety of (mainly) films and (some) rigids on offer, none of them are being sold in large quantities at this time. Instead, the most successful seaweed bioplastic product - Notpla’s meal container with 75 million units to be delivered over the next 3 years - is 99 percent cardboard with a little seaweed coating.

The meal containers are taking the opportunity (growing awareness of the negative consequences of PFAS and other petrochemical coatings), playing to the material’s strengths (solid grease barrier properties) and niftily circumventing its weakness (high price) by only having to add a tiny bit.

Other biomaterial companies have made a similar pivot. Soarce started out making textiles from seaweeds, but last year turned to enhancing the properties of industrial materials by adding a nanocellulose coating.

It makes sense. Most biomaterials (regardless of the source of biomass) struggle to break into the mainstream because of higher prices and lower material properties than incumbents. Seaweed-derived coatings instead add little to the price and have similar or improved properties compared to less sustainable legacy products. Here is an opening to build industrial capacity and create demand for seaweed cultivation.

….which leads us back to shrimp.

Back to shrimp? Yes, because while a variety of seaweed fractions and derivatives are used to create bioplastics, agar is central to many formulations at the moment. And almost all of the seaweeds used to make agar are dragged out of a pond somewhere in Indonesia.

So if co-culturing shrimp and seaweeds can improve productivity and profits, could this potentially lead to a lower agar price and thus improve the value proposition of certain seaweed bioplastics?

I’m not sure if that is how it works. Nonetheless, I would not be surprised if the near future sees more biomaterial companies copy Uluu and move further upstream to make their own ingredients: lower-grade, cheaper versions of what they are currently buying, tailored to their own needs. This will then get them one step closer to the raw material, with more power to influence the farmers to adopt best practices like IMTA.

Truth? No. Ideas, theories, fragments of lore. In the end, the sea is wide, and the far shore calling us is distant, behind the wave, beyond the blue horizon. So we continue to drift -seaweeds, plastics, keeper of the tale- away from the siren call of sureness, on tides we fail to name, hoping, sometimes for harbour, sometimes, for wind.