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The crate debate is the wrong question
One thing I like about Manna is that we are involved in so many different types of projects and discussions.
01 · The debate
Trays, belts and racks
Lately, one recurring topic has been trays vs. belt systems vs. racks.
Even though we can hardly call our industry mature or old, trays are the proven standard. Most of our CAPEX and OPEX calculations, recipes and estimates are based on concrete field data from 600 × 400 mm trays.
Belt systems are newer, but rearing BSF larvae in long beds—made from concrete or placed on racks—is not an entirely new concept. The difference is that with a belt, the rearing surface moves. This creates new advantages, but also the disadvantage of added complexity.
02 · Costs
CAPEX and OPEX per tonne
From a business point of view, profitability starts with finding the right combination of a) usable biowaste, b) local customers and c) a workable regulatory route. Production technology is therefore not the first decision in a high-level evaluation of a potential BSF business.
However, when the business case works, you want to keep the total CAPEX and OPEX per tonne of biowaste handled as low as possible. This is not as straightforward as it seems. Dozens of parameters affect the result, and different systems offer different ways to lower the cost.
To make things even more complex, you can decrease CAPEX but then pay for it through increased OPEX. The right compromise differs by region depending on electricity prices, wages and other local factors. Belt systems are interesting because they offer a potentially different balance between automation and manual labour.
03 · Capacity
Where belt systems fit
What is the best design and architecture at different production capacities? That is another important question.
With trays, you can start with one tray holding about 8 kg of wet substrate. The rest can be done manually. But when you start loading 500 trays per day—roughly 4–5 tonnes of substrate—you should re-evaluate the best approach. I don't know at what capacity the advantages of belt systems are greatest, or what the optimal tonnes-per-day module size is for modular scaling. This is what we need to understand better in practice.
04 · The verdict
Too few comparable cases
The verdict is still out, and I don't dismiss any of the approaches at this point. Each may find its place in different regions and at different production capacities. At the moment, however, we have too few successful cases and too little transparency to evaluate them on an apples-to-apples basis.
My wish for all BSF technology suppliers is that they start emphasising and demonstrating the benefits of their approach with metrics that we can compare across systems, as in other industries. We should not make systems difficult to compare. We should clarify their advantages so that buyers can make decisions with more confidence and avoid bad choices—increasing the number of successful BSF cases overall.
That is my two cents on this matter for now. More to follow.
Keep exploring
Related topics and pages
- BSF production course — the course that covers production stages and measurements
- BSF technology course — the course on climate control, facility design and Manna MIND
- Article library — the practical guides this post joins
Read next
- Modular or centralised is the wrong question — why facility architecture follows the waste, not the technology
- CAPEX in BSF production: What you actually pay for — the capacity chain from structure and climate control to harvest
- OPEX in BSF production: What really drives €/kg output costs — why feedstock, energy and yield consistency decide the operating cost
- FI practical AI series opener — a Finnish-language field note on phasing AI adoption for non-technical entrepreneurs
Next step
Compare the systems on one cost per tonne
Manna can help compare trays, belt systems and racks against the real biowaste, capacity and local costs of a case.