What KALARVO showed, and the next steps

01 · Findings

What the trials showed

The last piece in the KALARVO series: what three trial rounds showed, and what comes next before Kainuu fish side streams can feed black soldier fly larvae in production.

Three rounds and 70 recipes showed that all three fish side streams can technically be turned into larvae. There was no single best raw material or recipe; each side stream found its role: the lake-fish side stream as the base raw material, rainbow trout gut mass at a low share and in a dry mix to lift larval size, and the filleting side stream, once crushed, as a co-substrate.

On the process side, moisture in the mix was the most important common factor, and each fish side stream needs its own water setting. A seven-day cycle works when food and moisture last until day seven.

The recipe questions are answered: no new broad screening is needed, so the next phase can be small and focused.

02 · Route

The route to use

Raw fish side streams are not currently a permitted rearing substrate in Finland for insects grown for feed or pet food: the Finnish Food Authority's guidance and the EU list allow fishmeal, but not raw gutting or filleting side streams. The first step is therefore a route confirmed in writing for the exact product, raw-material and facility chain, or a move to a permitted substrate.

A side stream is valuable to a grower when it is consistent, ready to process and delivered nearby. Real delivery terms settle who collects, stabilises and crushes, and who carries the batch risk.

03 · Checklist

Before a fish side stream becomes a BSF raw material

What is needed

A written authority route

Why

A technical result is not a permitted use

Next step

Confirm the exact product, raw-material and facility chain with the Finnish Food Authority, or use a permitted substrate
Confirmation trials

Why

The winning recipes are known

Next step

One or two trials per raw material
Moisture windows

Why

The same water suited one material and drowned another

Next step

A measured moisture range per raw material at loading
Crushing

Why

Heads and bones limited mixing and yield

Next step

A practical crushing step to about 1–2 cm; grinding below about 2 mm reduces bioconversion
Mercury screening

Why

Mercury in the lake-fish larvae exceeded the feed-material limit

Next step

Screen raw-material batches and their species mix
Hygienised frass

Why

Frass needs heat treatment for fertiliser use

Next step

Hygienise and analyse the treated product
A local replacement for wheat bran

Why

Wheat bran is not available in Kainuu

Next step

Test a local moisture and structure ingredient
Recipe-specific climate

Why

Each raw material likely has its own optimum

Next step

Tune temperature and humidity for each winning recipe

04 · What this means

What this means

KALARVO gives a strong technical basis for a focused follow-up pilot once a permitted use is confirmed. The order matters: first the route, then a few confirmation trials and fixed moisture windows, and only then investment in pre-processing.

In KALARVO, the biology was solved before the permit, the logistics and raw-material consistency. That is worth remembering with any new side stream: much of its value is decided before the larvae eat their first gram.

The results of the whole project are in the summary report; the rest of the series covers each finding.

If you have a side stream of your own that you would like evaluated for larval rearing, get in touch with Manna Insect.

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.