The optimal temperature for mycelium growth is 24 -25 degrees Celsius. With lower temperatures mycelium develops slower at higher temperatures competitor moulds have the advantage. To approximate the optimal tunnel temperature over the entire compost layer a delivery temperature of around 23-24 degrees Celsius is recommended with a compost temperature in the upper layer of around 26 degrees Celsius.
With normal filling weights and sufficient fan capacity reaching these temperatures should be no problem. Problems only start to occur in the period that outside temperatures start to rise at night (in other words: the heat content).
Cooling is often not applied rigorously enough - particularly in the second week of mycelium growth when activity increases. This means the incubated compost is supplied to the grower too warm - with all the associated disastrous consequences.
To prevent this problem cooling systems should be installed in tunnels.
As relatively high delivery temperatures are used a variety of cooling methods can be applied. Cooling systems are also available in many shapes and sizes: fixed and mobile well water cooling cold water cooling freon cooling misting through the fan running water under the tunnel and even dry ice and nitrogen cooling when compost is delivered.
An effective and economic method is installing a sprayer pipe work underneath the tunnels.
Con Hermans, AdVisie ‘The mushroom cultivation advisors’