The site is close to housing
Enclosed fermentation with treated exhaust is usually the only way to hold an odour limit inside a residential or commercial area.
01
Vessel types and what each suits
| Type | Configuration | Best suited to | Engineering notes |
|---|---|---|---|
| Vertical tank with central agitator | Cylindrical or square tank, 5–150 m³, automated discharge | Small and medium plants, farms, sludge volumes up to about 30 t/day | Even filling and discharge, compact, needs careful agitator maintenance |
| Horizontal cylindrical reactor | Rotating or paddle-agitated drum | Continuous, uniform feedstock; medium capacity | Filling rate must match rotation or the process stratifies |
| Tunnel / channel reactor | Long concrete channels with moving agitator and aeration floor | Industrial plants, 20–200 t/day | Higher capital; excellent control and emissions management |
| Combined vessel + curing bays | In-vessel for thermophilic phase, covered bays for curing | Most commercial plants | Balances capital and control; curing bay volume sized on 2–4 weeks |
02
What the control system actually does
- Temperature control — probes at two or three depths drive blower speed and, where fitted, vessel agitation. Below 45 °C the blower runs less; above 65 °C it runs more to shed heat and protect the microbial population.
- Oxygen or CO₂ trend — the practical indicator of whether the air rate matches demand; it is what distinguishes a controlled process from a vessel that is merely closed.
- Aeration profile — intermittent or continuous air supply matched to the degradation rate, which is highest in the first three to five days.
- Exhaust treatment — exhaust air passes through a biofilter, acid scrubber or a combined system, because a closed vessel concentrates odour rather than removing it.
- Leachate handling — condensate and leachate collected and recirculated to moisture correction or treated.
- Records — vessel fill weight, temperature and air volume per cycle, so that a batch can be traced to the product it became.
03
Loading discipline — the reason vessels succeed or fail
A vessel that is filled with material outside its design range behaves worse than an open pile, because it has no tolerance to spare. Three rules decide the outcome: the moisture of the feed must be within the range the aeration design assumes, the mix must be consistent from batch to batch, and the batch weight must match the vessel's designed daily throughput — over-filling a reactor pushes residence time down and the material leaves immature.
For that reason an in-vessel plant usually includes a mixing and buffer section sized for two to three days of feed, and a batch record system that links the feed to the vessel cycle. Where the plant handles sludge or food waste, a shredder and a magnetic separator upstream are effectively part of the vessel scope.
04
When in-vessel is the right answer
Land is scarce or expensive
One fifth to one third of the footprint of an open windrow system for the same tonnage.
The climate is extreme
Cold winters and monsoon seasons are handled by the vessel rather than by the pile.
The feedstock is wet or odorous
Sludge, food waste and pig slurry are far easier to control inside a vessel with forced aeration.
Specify an in-vessel system
Send the daily tonnage, feedstock moisture and the odour constraint at the site; we return the vessel sizing, aeration demand and exhaust treatment scope.
FAQ
Plant engineering questions
How long does in-vessel fermentation take?
Seven to twelve days for the thermophilic phase in a controlled vessel, followed by two to six weeks of curing outside it. Plants that discharge material and bag it immediately usually find it re-heats and forms condensation in the bag.
How is vessel size calculated?
Daily volume of fresh material divided by bulk density, multiplied by residence days, plus 10–20% headroom for filling and discharge. For 20 t/day of manure at 0.7 t/m³ bulk density over 10 days, that is roughly 320–380 m³ of working volume.
Does in-vessel composting need a biofilter?
Almost always, where the site has neighbours. The vessel concentrates exhaust into a small volume, which makes treatment feasible and cost-effective; without treatment the odour leaves through one stack instead of a whole field.
Can a vessel be added to an existing plant?
Yes — the most common configuration is a retrofit where an under-performing open pile is replaced by one or two vessels feeding the existing processing line. The layout needs space for the buffer and discharge conveyors.
Send us your design basis
Tell us the feedstock, the daily tonnage and the product you want to sell. The engineering team replies with the plant configuration, the equipment scope and the information we still need before layout drawings start.
- Feedstock profile — type, moisture, contamination, seasonal peaks
- Capacity — t/day fresh material or t/h finished fertilizer
- Product — powder, granules, bagged retail, bulk compost
- Site — available area, power supply, water, access road
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