Mushroom Production Equipment: Mixing, Bagging, Sterilisation and Room Climate

One line, one chain of duties

Bag or block mushroom growing runs as a chain: ingredients are screened and weighed, mixed with water, filled into bags, sterilised, cooled and inoculated, then incubated and fruited in climate-controlled rooms. Each machine must keep pace with the one after it, so the mixer, the bagger, the steriliser and the rooms are best specified together. The mushroom-equipment range on the site covers the mixing and climate ends of that chain.

Start with three facts about your own operation: the species, the recipe, and the number of bags per day. Every figure below follows from those.

What the recipe asks of the mixer

Supplemented sawdust recipes are written as percentages of dry weight. A University of California example uses 76 percent oak sawdust with 12 percent millet and 12 percent bran, wetted to 65 percent moisture; others add gypsum or calcium carbonate at a few percent [2]. Because each ingredient arrives with its own moisture, the water to add has to be calculated from the moisture content of every component [2]. The same guidance suggests coarse sawdust mixed with wood chips at about two parts to one [2], and an orchard branch chipper is one way growers produce hardwood chips from prunings.

For the mixer this means two jobs: blend a small share of fine supplement evenly through a bulky base, and bring the whole batch to a target moisture without wet lumps. Upstream, a vibrating cleaning sieve and a magnetic separator keep stones, wire and oversize pieces out of the screw feeders, and a screw or scraper conveyor or a mobile belt conveyor moves bulk sawdust to the mixer. Guangchang builds such handling equipment for grain plants, and the grain-processing machinery section lists more.

Specifying a substrate mixer

Ask first whether a quoted volume is the vessel or the working batch. The Guyou 6 m³ substrate mixer is a good example of why: turning cubic metres into kilograms of wet substrate needs the bulk density of your recipe and the maker's permitted fill level. Give Longquan Guyou your recipe, moisture target and bags per shift, and ask for the working batch in kilograms.

Then ask for the mixer type and drive power, the full cycle time from loading to empty, how water is added and metered, how uniformity is checked, how much material is left behind after discharge, and where the outlet sits relative to your bagger or screw feeder. Stainless contact parts and easy cleaning matter, since residue left in a wet mixer spoils between batches. Batch output per hour should exceed the bagger's rate so the filling line never waits.

Bagging and sterilisation

Added nitrogen in supplemented sawdust raises the risk of contamination, so these bags are sterilised rather than pasteurised [2]. UC Extension sterilises at 121 °C and 15 psi (about 1 bar gauge), autoclaving sawdust-filled bags for 90 minutes or more depending on volume and the number of bags; larger sawdust loads may need 2 to 4 hours [2]. Straw for oyster mushrooms can instead be pasteurised in water held at about 160 °F for one to two hours [2].

This makes bag size and filled mass the link between bagger and steriliser: they set how many bags fit a cabinet load and how long heat takes to reach the core. Guyou sells bagging and sealing units, sterilisation cabinets and a biomass boiler, so ask for the load per cycle, the temperature and pressure programme, and the heat source as one package.

Autoclaves, boilers, steam pipework and refrigeration plant are all pressure systems in the eyes of the UK Health and Safety Executive. Its guidance asks for equipment built to recognised standards, known safe operating limits, working safety valves that discharge to a safe place, written operating instructions, trained operators and a maintenance programme [3]. Ask the maker which pressure-equipment standard the vessel is built to and which documents ship with it.

Growing-room climate targets

Climate needs change through the crop, and the climate unit must reach every stage. UC Cooperative Extension gives these figures for oyster mushrooms: spawn run at 90 to 100 percent relative humidity, with carbon dioxide tolerated up to 20,000 ppm and no fresh air; pinning at 95 percent humidity, 55 to 60 °F, CO2 below 600 ppm and four fresh-air changes an hour; cropping at 85 to 92 percent humidity, 60 to 64 °F, CO2 below 600 ppm and four to six air changes an hour [1]. Shiitake crops at 85 to 90 percent humidity and 59 to 68 °F with CO2 below 1,000 ppm [1].

Colonising substrate also makes its own heat. UC notes that bags self-heat during incubation, should be spaced about an inch apart, and become prone to contamination as they approach 100 °F, while the incubation room is held near 75 °F with fresh air [2]. That heat is a real cooling load on the unit, on top of the building and the incoming outside air.

Specifying a climate unit

Size fresh air from the CO2 target first: room volume times the air changes per hour gives the fresh-air flow, so a 200 m³ cropping room at four to six changes needs roughly 800 to 1,200 m³/h of outside air. The unit then has to cool or heat that air, remove substrate heat, and hold humidity, all at once.

When you ask Ferdlis New Energy or any other supplier for a selection, send room size, number of rooms, substrate mass per room, species and stage programme, and your hottest and coldest outdoor design conditions. Ask for one duty sheet showing cooling and heating output in kW at room conditions, recirculation airflow at stated external static pressure, the fresh-air share, the humidifier type and output, and the CO2, temperature and humidity sensors. Ferdlis lists FAEH units with direct refrigerant circuits and a FAZK series on water or glycol for button mushrooms, which follow their own casing and cropping programme; ask for a design to yours.

Smaller rooms often add recirculation fans from makers such as Sanxin and simple misting. UC's small-farm example ran low-flow misters on overhead PVC lines from a timer [1]; an eight-station irrigation controller and solenoid valves can zone the same idea across several rooms, using parts from the irrigation section.

What to send with the enquiry

For the mixer: recipe by dry weight, ingredient moisture, target moisture, bags per shift, bag size and filled mass, and how material arrives and leaves. For sterilisation: bag count per load, heat source, utilities and the pressure-equipment documents you need. For climate: room drawings, insulation, stage programme with temperature, humidity and CO2 targets, and outdoor design conditions. A single specification sheet sent to every supplier makes the quotations directly comparable.

Source notes

[1] University of California Cooperative Extension, San Benito and Santa Clara Counties — Cultivating Mushrooms on Small Farms, M. de la Fuente (2011 (upload date)) [2] University of California Agriculture and Natural Resources — Sawdust as Substrate (recipes, sterilisation and incubation notes) (2011 (upload date)) [3] Health and Safety Executive (UK) — Pressure systems: A brief guide to safety (INDG261 rev2) (2012 (page updated 2025))