Prevention is better than cure

Points of attention with incubated compost in bulk

The bulk production of incubated compost is a rapidly growing business worldwide. At first sight, it may appear to be the simplest process of all the production phases in the mushroom chain, but the results often fall short of expectations. This is sometimes due to the wrong type of tunnel design, but the main causes are more often lack of expertise and less than perfect discipline regarding hygiene. The most important points to be considered are summarized below.

By Rudi Joris, Dalsem Mushroom

As with many things, good groundwork is the key to success. This also applies to the production of incubated compost. During the design stage of the tunnel it is very important to consider the various construction aspects, such as good separation of the individual tunnels. One of the ways to achieve this is by placing double walls and sealing the plenums correctly, even with higher pressures.

Other components that add up to a good tunnel construction are the quality of the concrete with correct expansion joints and good water seals in the drainage system. In practice however, far too often the first mistakes are made here and the production of good quality incubated compost is doomed to fail before it has even begun.

Rotate tunnel use

When designing tunnels, it is important to bear in mind that rotating use of tunnels is preferable. This means that a tunnel must suitable for multi-functional use and not just for pasteurisation (phase-2) or incubation (phase-3).

After incubation it is always better to pasteurise the tunnel to effectively destroy as many infections as possible. This means that cook out can be omitted, which will not only save wear and tear to the tunnel but also energy costs. This method is not often used, particularly if there is only a small number of a tunnels. But sometimes, in spite of cook out, infections will often crop up after a period of time.

If possible, we advise flooding the plenum under the slatted floor before starting to steam. This method avoids a layer of cold air hanging just above the surface of the floor, which would otherwise prevent thorough disinfection.

Work discipline

It is vital to give clear instructions to personnel, so that each employee knows his or her responsibilities and is aware of the importance of good hygiene. Ensure one person is designated to make sure that personnel remain motivated and comply with the regulations. A hygiene checklist can be used to call attention to general organisation and logistic processes. Personnel must remain alert at all times, and clean clothing and disinfected boots are essential during spawning. Entering and leaving the spawning area during spawning should be absolutely forbidden.

Carry out spore pressure measurement two or three times each year to trace any possible sources of infection and allow preventive measures to be taken.

Hygiene in the tunnel

Don't use too much formalin when disinfecting. It is better to make plentiful use of water. Ensure that all compost residues, even in the smallest corners and gaps in the machinery, have been removed. Each tiny piece of compost can be a potential source of disease.

Then the hall must also be meticulously disinfected, closed and overpressure applied using an overpressure unit with enough filtering capacity. The same rules apply when loading compost into the trucks; make sure all equipment is perfectly clean and kept clean!

The air conditioning system is also highly important. Leaks or incorrect pressure in the tunnel can allow unfiltered air - and infections- to enter the tunnel.

Use good quality fine filters and ensure these are regularly checked and replaced as necessary.

If supplements are used make sure they are thoroughly mixed through the compost, and only use new sacks that are completely closed. Never use supplement from half-open or damaged sacks.

Flies are also a major carrier of diseases, so make sure there are none in the tunnels. Anti-fly spray or other products can be used on the compost before the doors are closed. Also ensure adequate filtering on e.g. overpressure openings.

Hygiene in the growing room

Attention to hygiene doesn’t end in the incubation tunnels. When the growing rooms are filled the same aspects of hygiene awareness should be observed. Disinfect machinery before use. Don't walk through the work corridor when the rooms are being filled and don't enter ‘dirty' growing rooms. Make sure that employees always wear clean clothing and footwear.

If the following guidelines are not taken seriously by all involved, the first signs of infection will develop within a matter of time  - a nightmare scenario for the composter. Greenish moulds in particular are the greatest hazard, as they are easily spread by all types of carriers such as clothing, machinery, pallets, etc.

To sum up, a well-thought out design for the tunnels and installations, but above all inspecting and observing strict hygiene regulations are essential to keep the risks of infection in and around the incubation tunnels under control. The result will be improved compost quality and better working conditions for all concerned at the tunnel facility.

During the design stage of the tunnel it is very important to consider the various construction aspects, such as good separation of the individual tunnels.