Technically yes, legally not yet

01 · The question

KALARVO showed that all three Kainuu fish side streams it tested can be turned into black soldier fly (BSF) larvae. Whether that becomes a business depends on two things outside the rearing container: the legal route, and the condition in which the side stream arrives.

This article is part of the KALARVO results series; the summary report covers the whole project.

02 · Technical result

Technically yes

Three rounds and 70 recipes showed that lake-fish side stream, rainbow trout gut mass and rainbow trout filleting side stream can all be converted into larvae. The lake-fish side stream was the most reliable, with no failed batches in three rounds. There was no single best raw material or recipe; each stream has its own role and its own fish share.

03 · Legal position

Legally not yet

The Finnish Food Authority's current guidance and the EU list of permitted animal-origin substrates for farmed insects (Regulation (EU) 2017/893) include fishmeal, but not raw fish or the side streams from gutting and filleting. Raw, frozen or acidified fish side streams are therefore not a permitted substrate today for insects reared for feed or pet food. For lake fish there is a second gate: the larvae's mercury exceeded the general limit for feed materials: the mercury findings

The route forward is to confirm the exact product, raw material and facility chain in writing with the Finnish Food Authority before commercial use. A use outside the feed chain needs its own assessment. This is the report's reading of the rules, not legal advice.

04 · Value

The value is set before the larvae

The trials show which properties make a stream an asset for the grower and which make it a handling task.

Side stream

Lake-fish side stream

Shown in the trials

Most reliable raw material; no failed batches

Handling challenge

Biggest crushing need; larval mercury above the feed limit

In-principle reading

Can be valuable if consistent, process-ready and delivered nearby
Trout gut mass

Shown in the trials

High larval-size potential

Handling challenge

Moisture and batch risk

In-principle reading

Value is conditional; wet or variable material may need a handling fee
Trout filleting side stream

Shown in the trials

Works as a co-substrate; larvae below heavy-metal limits

Handling challenge

Crushing, clumping, odour risk

In-principle reading

Depends on pre-treatment and on who handles crushing and logistics

In short: collection, stabilisation, crushing, moisture control and batch risk decide whether a side stream is valuable to the grower or needs a reception fee.

05 · Process needs

What the process needs

Crushing. Fish parts such as heads and bones need real mechanical crushing before mixing, but not to powder: grinding too fine weakens bioconversion. Scaling needs a proper pre-treatment step.
Moisture per raw material. Recipe moisture is the main control, set for each stream. One shared water setting does not suit all.
Temperature second. Around 33 °C shortens the cycle; a few degrees lower lengthens it. Keep air humidity at 70 % or higher to slow surface drying.
Consistency and logistics. A stream that arrives at a steady quality, ready to process and from nearby is worth more than one that varies batch to batch.

06 · What this means

What this means

No broad new recipe screening is needed. The next stage is a written confirmation of the permitted route, one or two confirmation trials per fish raw material, a locked moisture window for each stream, a practical crushing solution, mercury screening for lake fish, and real supply, cost and use terms. The technical base is strong. The route and the raw-material terms now decide the business.

If you have a side stream you want evaluated, get in touch.

Kajaani University of Applied Sciences (KAMK) procured black soldier fly larvae rearing trials on Kainuu fish side streams as part of the KALARVO project (Processing fish side streams into value products). Manna Insect carried out the trials as the contractor, responsible for the trial design, measurements and analysis. Co-funded by the European Union.