The most revealing part of a seafood processing line isn’t always what ends up on the plate – it’s what doesn’t.
Watch long enough and you start to see the hidden geometry of “yield”: fillets trimmed for uniformity, skins separated for texture, frames and bones pulled aside, shells piling up in bins that would look like waste anywhere else. In most food categories, those piles are a cost center. In seafood, they’re increasingly treated like inventory—raw material for a second (and sometimes third) product life.
Pacific Seafood uses an unvarnished term for this stream: “rest protein,” a catchall for the bones, skin, and shells left behind after primary processing. In its 2024 Corporate Social Responsibility (CSR) Report, the company says it operates with a “100% fish utilization goal,” transforming rest protein into “usable fish meals and oil, fertilizer, pet food, and much more.” The same section puts a hard number on the scale of that effort: Pacific reports it prevented 49,114,703 pounds of rest protein from entering U.S. landfills in 2024 by turning it into usable products.
That’s the thesis of the circular economy in seafood, stated plainly: the “waste stream” isn’t just something to manage—it’s something to design.
The Uncomfortable Truth: Byproducts Are Not a Rounding Error
A lot of people still think of byproducts as scraps—minor leftovers after the “real” product is made. Industry groups focused on marine ingredients argue the opposite: as processing scales up, byproducts can represent up to 70% of processed fish, depending on species and processing type.
Zoom out further, and you see why the stakes are global. FAO’s State of World Fisheries and Aquaculture (SOFIA) 2024 reporting notes that 11% (20.8 million tonnes) of aquatic animal production was destined for non-food purposes, and that about 83% (17 million tonnes) of that non-food share was reduced into fishmeal and fish oil. The headline isn’t “fish becomes feed.” The headline is that the sector has already built a parallel economy around what doesn’t get eaten directly.
This is where the circular-economy argument starts to harden into something measurable: even modest improvements in byproduct capture can shift millions of pounds away from landfill, while creating inputs for aquaculture, agriculture, pet food, and even materials science.
“Industrial Symbiosis”: When Your Leftovers Become Someone Else’s Inputs
The most mature version of waste-to-value is bigger than any one company. It’s what sustainability people call industrial symbiosis: one company’s byproducts become another company’s feedstocks, with the shared goal of keeping material out of landfill and extracting more economic value per pound harvested.
Pacific Seafood explicitly flags industrial symbiosis as a strategic focus, saying it has been working with legislators and local leaders to identify opportunities to collaborate with local businesses and “utilize our byproducts.” The CSR report notes that in 2024 its EHS Director traveled to Denmark to learn from industrial symbiosis experts, and that Pacific began “process flow mapping” to track materials and resources as a first step toward partnerships.
That mapping work is the opposite of glamorous—but it’s the backbone of circularity. You can’t “upcycle” what you don’t measure. You can’t build partnerships if you can’t describe your outputs with the same precision you use for your sellable product.
Turning Fish Into Fishmeal and Oil Without Making “Waste” Someone Else’s Problem
Fishmeal and fish oil sit at the center of the byproduct conversation because they’re both economically important and politically loaded. When they’re made from whole fish caught specifically for reduction, they raise hard questions. When they’re made from trimmings and frames that would otherwise be discarded, they look like resource efficiency.
Pacific’s CSR language is careful: it describes converting rest protein into “fish meals and oil” among other products. That aligns with the broader direction FAO and marine-ingredient groups emphasize: a growing share of marine ingredients is produced from processing leftovers rather than targeted catch.
The circular-economy win here is straightforward: if aquaculture and pet food demand exists (and it does), then using byproducts to meet part of that demand can reduce pressure to source additional raw material.
But the deeper win is operational: rendering (done well) is a stabilizer. It turns a perishable stream into shelf-stable ingredients, reducing odors, hauling frequency, and disposal risk—while also creating a product that can be sold.
Shells: From “Mess” to Habitat and Soil
Shellfish waste is the most visually dramatic byproduct category: mountains of shells, heavy and mineral-rich, often concentrated in short seasonal windows. It’s also one of the easiest for the public to understand—because shells can become reefs again.
Pacific’s CSR report describes a striking example of shells-as-infrastructure in its Chesapeake Bay restoration project. The company says years of harvesting and exporting left the public oyster fishery short of shells needed for reproduction and growth, so Pacific partnered with Madison Bay Seafood and Wittman Wharf Seafood to move “millions of Pacific oyster shells” from its South Bend, Washington facility to Maryland, where the shells will be used to create new oyster reefs. The report quantifies the logistics: 84 truckloads and 25,000 miles traveled from South Bend, WA to Toddville, MD.
Even the “inside baseball” detail is telling: the report notes the project faced skepticism from Maryland’s Department of Natural Resources over introducing Pacific oyster shells, and that research led by a Virginia Institute of Marine Science pathologist supported safety and compatibility for regulatory approval. The message is implicit but important: circular economy isn’t just engineering—it’s governance and ecological risk management.
Shells also have a second life on land. Pacific’s public materials for its bio-products division describe making fish- and shellfish-based organic fertilizers and ingredients for feeds and pet food. A Pacific page on organic fertilizers (captured in search results) notes crustacean shells such as Dungeness crab and Pacific pink shrimp shells contain polysaccharides associated with plant growth and stress resistance.
And the independent market around this is real: multiple agricultural suppliers describe fish hydrolysate fertilizers made from processing residuals that include crab and shrimp shell.
The “High Value” Frontier: Chitin and the Materials Economy
If fishmeal and fertilizer are the established end uses, chitin is where the byproduct story starts to feel like the future. Chitin is the structural polymer in crustacean shells, and when it’s processed into chitosan it shows up in everything from biodegradable materials to water treatment.
A 2025 peer-reviewed paper on chitosan from crustacean shells reports shell chitin content “typically ranging from 14 to 35%,” underscoring why shell waste is treated as a feedstock rather than mere trash. A separate research review notes the crustacean processing industry generates shell waste at scale and that it can be utilized to produce chitin and chitin nanomaterials for a wide range of applications.
This matters because it reframes “waste to value” from a disposal workaround into a materials pipeline. The same shells that can become reef substrate or soil amendments can also become industrial inputs—if the economics and processing infrastructure line up.
What Makes a Circular Program Credible (And What Still Needs Sunlight)
The most persuasive “waste to value” programs tend to share a few traits:
- They quantify output, not just intent. Pacific’s landfill-diversion figure—49,114,703 pounds of rest protein repurposed in 2024—is exactly the kind of metric that makes a circularity claim testable.
- They name the pathways. Rest protein becomes fishmeal/oil, fertilizer, pet food, and more—not “reused” in the abstract.
- They show the awkward parts. Shell recycling across the country isn’t a cute sustainability photo; it’s 84 truckloads and 25,000 miles—plus a regulatory conversation about ecological compatibility.
What’s still often missing in corporate circular-economy stories (Pacific included, at least in the passages cited here) is a more detailed accounting of the downstream split: how much goes to feed vs. fertilizer vs. other uses; the carbon/energy footprint of processing those streams; and how the company evaluates tradeoffs (for example, when a higher-value pathway demands more processing energy). Pacific does describe early-stage “process flow mapping” work for industrial symbiosis, which suggests that more granular resource accounting is on the roadmap.
The Takeaway
Seafood processing will always generate byproducts. The circular-economy question is whether those byproducts become a liability—or a second harvest.
In Pacific Seafood’s telling, the goal is to treat rest protein as a resource stream with multiple destinations, backed by a measurable landfill-diversion result (49,114,703 pounds in 2024) and tangible, place-based projects like shipping shells across the country for reef restoration (84 truckloads, 25,000 miles). Add the broader context—byproducts can represent up to 70% of processed fish and a significant share of global aquatic production already routes into non-food uses with fishmeal and fish oil as dominant pathways —and the “waste to value” story stops being niche.
It becomes one of the main ways seafood tries to square growth with stewardship: use more of what you already took from the water, and make every pound count twice.
