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Here I would love to share with you our travels and adventures as international mushroom consultants. MEMOIRS about husband Pieter Vedder, who was a SCIENTIFIC PIONEER in Mushroom Cultivation Education. His practical handbook is in 8 languages and is called the MUSHROOM BIBLE: https://mariettesbacktobasics.blogspot.com/2018/03/1978-pjc-vedders-modern-mushroom.html

Thursday, July 30, 2020


This is some interesting history about how we came to COOLING IN MUSHROOM HOUSES, right from the pioneering times...
In Nature, mushrooms only develop during the cooler season. But by commercially growing them year round, we have to do something during summer time.
We should however, not make mushrooms feel miserable...
Although most people look longing for summer, a mushroom grower gets the fright of his life when the outside temperature rises to summer values. The mushrooms like to have a temperature of 15-17ºC and it becomes difficult to keep it cool inside the rooms at outdoor temperatures of 25-30ºC. This especially when the heat period lasts a bit longer and night temperatures also increase.
At temperatures in the growing rooms of 18-20ºC, the mushrooms grow quickly and open prematurely, so that the quality deteriorates greatly. At these higher temperatures and therefore greater activity of the mycelium and the growing mushrooms, the production of carbon dioxide becomes much greater.
It is known that with an increase in temperature of 1ºC, carbon dioxide production increases by 20%. This means that in a warm period with high temperatures in the growing rooms, additional ventilation should be done to keep the CO₂ content low enough. However, a lot of ventilation means that, especially during the day, warm air is brought into the rooms, which can increase the temperature even further. Non-ventilation during the day means that the CO₂ content in the rooms is too high, which greatly reduces the quality and can cause the buttons to die. At such a time, a mushroom grower is virtually powerless or he should have a cooling unit.
We in the Netherlands have little experience with the use of coolers in mushroom cultivation. We cannot therefore say from experience what capacity such a machine should have in order to keep the temperature at e.g. 15ºC. We have therefore started to calculate whether we could find out something this way.
Heat production
The starting point in this calculation was the production of carbon dioxide. Everyone knows that CO₂ is produced by the burning off of carbohydrates using oxygen and that heat is released. From all kinds of studies we know quite accurately how much carbon dioxide per kg of compost is produced. According to researchers, a maximum of 0.10 grams of CO₂ per kg of compost (e.g. in a second break) produced by the hour. 
If we claim that we use about 100 kg of compost per square meter in our growing rooms, CO₂ production would be 100 x 0.10 grams = 10 grams per square meter per hour. 
It is known ¹) how much Kcal. are released at the burning off of carbohydrates according to the
formula  C₆H₁₂O₆ + 6O₂→ 6CO₂ + 6H₂), namely 674 Kcal. We also know that during the harvest 
period 10 grams of CO₂ is released per square meter per hour. From this it can be calculated that per square meter per hour there is 10 : 264 x 674 = 25.5 Kcal. heat release. 
We have to bear in mind that not all energy released at the burn off (relief) of carbon is converted into
heat. Some of the energy released is recaptured when other formations are built. 
If we agree that 70% of the released energy is converted into heat, then 1 square meter bed with a heavy break would still deliver about 18 Kcal per hour. 
¹) 180 grams C₆H₁₂O₆ + 192 grams O₂   264 grams CO₂ + 108 grams H₂O + 674 Kcal.
For a growing room of 180 square meters of growing surface, this would mean a heat production of 180 x 18 = 3240 Kcal. by the hour. At higher temperature, activity increases and so does carbon dioxide production and heat production. 
This shows that one has to try to keep the temperature immediately low at the start of the heat period. Let's say the amount of heat released from the beds, however on average to 3300 Kcal. hourly per room.
This heat production of the beds can still be calculated in many ways, but even then one always comes close to this number.
Radiation (irradiation)
Besides the heat production of the beds, due to the activity of the living mycelium and the growing mushrooms, we also have to deal with a temperature increase in the growing room at high outdoor temperatures due to radiation.
We set the average ambient temperature at 25ºC for three room walls and the ceiling. It may be that a long room wall has a slightly lower temperature, if there is a harvest period room next to it. On the other hand, the temperature on the ceiling will be a bit higher. Furthermore, we can state that the temperature on one long side of the room is 55ºC, when pasteurizing in the adjacent room. We then come to the following calculation: 1 long and 2 short room walls:
{(15x3.20) + (2x5.20x3.20)} x
 (25-15)x 0.7                                                 =    569 Kcal.
1 long room wall, pasteurization side:
 (15x3.20) x (55-15) x 0.7                             =  1344 Kcal.
 (15x5.20) x (25-15) x 0.4                             =    312 Kcal.
                                                           Total       2225 Kcal.
There is, of course, the possibility that, in addition to the room to be cooled, in the adjacent room will not be pasteurized. On the other hand, the room to be cooled, perhaps has a long wall as an outer wall, so that the temperature on that side is higher. That's why we're keeping it at 2300 Kcal. for the irradiation.

The third possibility that allows the temperature in the rooms to rise in hot weather is the necessary ventilation.
We assume that the air content of the rooms is refreshed on average 5 times per hour during a decent production. We also assume that the air outside has a temperature of e.g. 25ºC and should be cooled to 15ºC. If we set the contents of a room at approximately 230 m³, 5 x 230 = 1150 m³ of air must be refreshed and cooled per hour. When cooling, 1150 x (25-15) x 0.31 Kcal =  ± 3400 Kcal. must be removed from the ventilation air.
Altogether we now arrive at 3300 (heat production beds) plus 2300 (irradiation) plus 3400 (ventilation) = 9000 Kcal. by the hour. Now it can be said that by warm weather outside it is only a few hours a day 25ºC and the nights are much cooler. This is indeed the case, but on the other hand, the 9000 Kcal. referred to has no overcapacity in case it becomes 28ºC. Also, there is still no cooling from e.g. 25 to 15ºC after casing.
That 9,000 Kcal. cooling capacity is only needed to keep the temperature at a certain value during the harvest period. On the other hand, of course, one can allow a 1 degree increase during the day and gain something at night by cooling the beds and the space to e.g. 14ºC, so that one has some reserve during the day. 
If we want to reduce the temperature from 25ºC to 15ºC in two days after casing, this again requires a considerable extra capacity. Everyone understands that the heat production of the beds during mycelium growth and immediately after casing is enormous. However, we assume that the temperature increase of the beds can be controlled by the ventilation and that the cooling of the compost with casing must be done by the cooler. Let's say that there is 18 tons of compost in the beds with 5 tons of casing and we assume that the specific heat of this material is 0.7. In order to cool this quantity of material (apart from the racks, etc.) from 25 to 15ºC, it is necessary: 
23000 x (25-15) x 0.7 = 161000 Kcal. in 48 hours. This will be approximately 3350 Kcal per hour. In addition, the entire building mass, walls, floors, ceiling, etc. needs to be cooled down, but let's assume that a cooler night brings some relief to this.
Another question is also whether it is economically justified to install a cooler with a capacity that is tailored to some extreme days. Anyway, the amount of Kcal. that should be able to be taken away appears to be ever bigger than we initially thought. Last year we gained some experience at the Experimental Station with a General Electric cooler, with a capacity of 2800 Kcal. on a room of approximately 66 m² of growing surface. This machine could indeed keep the temperature rise within limits, but there was no question of cooling. 
For a commercial mushroom farm with rooms of about 180 m² of growing surface, it also shows that in order to maintain a certain temperature in hot summer weather, certainly a cooling capacity of 9000 Kcal. per room per hour will be necessary. In order to absorb that amount of heat, a fairly large amount of air is needed. This means that strong air movement in the room is necessary. The relative humidity of the air will go sharply down from cooling down and then warming up. A strong air movement with air of low humidity again causes problems with regard to drying out of the beds and the scaliness of the mushrooms. That may be next time.
We are aware that this case has been approached theoretically in the foregoing and that there is room for criticism on all sides. We hope that this criticism will also come, especially from people who can say something about this matter. We have made a start because practical experience is lacking. This theoretical approach may help us to have practical experiences more quickly.
P.J.C. Vedder
A. Oversteyns
Line art by: M.B. Oversteyns-Reynaerts
This is only of interest to those within the Mushroom Growing business...
Written 1966-5 for CHAMPIGNONCULTUUR


  1. Liebe Mariette,
    das ist ein interessanter Post
    Sonnige Grüße

    1. Liebe Elisabeth,
      Ja, alles was lebt und wächst auf unsere Erde versucht zu existieren!
      Liebe Grüße,

  2. Hello Mariette, Of course Pieter's writing is mushroom-specific, but ideal temperature conditioning is of overall importance, especially these days when people demand perfect produce, but fuel to cool and heat is increasing expensive, both financially and environmentally. I also am experimenting with ways to control the summer heat in my apartment, and regulating heat exposure and air flow for people follows the exact same rules.

    1. Dearest Jim,
      Because of the low cost of energy in the USA, people are not so much interested in saving energy. Keeping doors open, spending less on insulation, etc. In the mushroom industry it all is a question of money. ~Pieter

    2. Hello again, In Taiwan, the cost of energy is high to begin with, and it increases geometrically, so the cost of, say, air conditioning two rooms is a lot more than twice the cost of air conditioning just one room. It makes you very aware of using and wasting energy. --Jim

    3. Dearest Jim,
      Who knows has the energy cost played also a role in the development of Taiwan's (Formosa then) once leading position in the mushroom industry. We both know the differences between high cost in the Old World countries versus the USA, at least here in Georgia it is very cheap. That even includes water. Our home is very well upgraded to the maximum insulation capacity, that got instilled in us from our upbringing. We spend quite a bit of money into that but you save energy later on.

    4. Pieter also mentioned that shade helps a lot! We have huge trees around our home.

  3. Hello dear Mariette!
    Great post and very interesting informations about the mushrooms and the ideal temperature they need to grow!
    Thank you for sharing! Have a lovely weekend and a happy August! Take care! Stay safe! Hugs!

    1. Dearest Dimi,
      Well, this post also shows that it is not that easy for growing quality mushrooms that look happy and sell thus for high market value.
      Hard to believe that July is gone... Happy August to you as well.

  4. Honestly Mariette I had no idea how complicated the mushroom industry is. The uncertainty of the weather each day must be a problem. Here in Perth in summer it can be 36C one day and more than 10 degrees cooler the next, even we get confused, I can imagine hard the mushrooms would find that! Happy weekend to you both ✨

    1. Dearest Grace,
      You seem to be a keen observer and good reader. Yes, growing mushrooms is a very complex crop and demands constant accurate interaction with keeping the optimum growing conditions. Yet, lots of turn key project companies talk others into building a big facility, and promising an easy production with the help of the technique. They forget to mention how demanding it is and how knowledgeable a grower must be for constantly adjusting and fine tuning the optimal growing conditions. Growing quantity is easy but growing quality is not easy at all. Quality is the outcome of a happy mushroom that grew under optimum conditions and on a perfect substrate with the right nutrition.

  5. Wow, it gets really complex. Sounds like considering various elements is important and necessary. I thought the relationship between temperature and wall length was interesting!

    Love the cute illustration :-)

    Have a great weekend, Mariette!

    1. Dearest Tamago,
      Yes, it indeed is a rather complex science and a grower ought to have some basic understanding of it all, for being able to correct timely and in a positive way.
      Yes, she did a wonderful job in creating some stressful expression.
      Happy weekend and hugs to you,

  6. You do a greate job with the mushrooms,
    thank you for the comment on my blog,
    Have a lovely day,

    Hugs, Ida

    1. Dearest Ida,
      Thank you for your visit here.
      Mushrooms have been a life long passion for both of us!

  7. Interessant Mariette, daar denk je als consument niet altijd over. Dan waren de grotten waar een constante temperatuur heerst een goede plek voor de champignonteelt.
    Fijn weekend en lieve groet.

    1. Beste Willy,
      Ja, je beseft soms niet half wat er aan vooraf gaat om iets te kweken en op de markt te brengen voor de consument. De grotten waren perfect maar het was een trage cyclus met langzame groei en dus niet rendabel om van te kunnen bestaan.
      Fijn weekend ook aan jullie en liefs,

  8. Hoi Mariette, ik volg je blog nu al een aantal maanden. Heel interessant! Vooral de rol van de NL champignonsector wereldwijd. We zijn nu, samen met de NL champignonsector, bezig om een Dutch Mushroom Center te realiseren op de Brightlands Campus Greenport Venlo. Een plek waar kennis ontwikkeld wordt en bezoekers worden meegenomen in de wondere wereld van de champignon(sector). Kevin, Mushroom Valley

    1. Beste Kevin,
      Als je mijn blog al een aantal maanden volgt, dan heb je ook wel gelezen dat mijn Pieter, de oprichter van het zeer succesvolle Centrum voor Champignonteelt Onderwijs (CCO) was. Met hart en ziel heeft hij dit eigenhandig opgericht en het was nogal bitter te moeten zien dat zo'n prachtige praktijkschool aan de grond ging.
      Waarom was er na hem niemand meer die dit kon voortzetten, met hetzelfde enthousiasme? Het is nu per 1 augustus net 37 jaar geleden dat we vertrokken naar de USA.
      En dan begint men met de resurrectie van een nieuw champignon centrum?
      Over de jaren hebben we al heel wat artikelen van 'famous' experts gelezen die allemaal de verkeerde vaktermen gebruiken. Een trouwe vorm van plagiaat van Pieter's Engelse boek, dat door een niet champignon-kundig persoon is vertaald. Die kon je zoiets niet kwalijk nemen maar iedereen, die voor geeft de vakkennis meester te zijn, wel.
      Men vergeet ook dat het legale copyright levenslang is + 70 jaar.
      Goed dat je uit de marketing sector komt, dat is nog altijd een erg belangrijk onderdeel. Je kunt onder mijn Label: Mushroom Quality Criteria (onder mijn blog staan ze allemaal) nog e.e.a. vinden.
      Ook kunnen jullie nog veel leren van Mushroom Canada, zie o.a. mijn post: https://mariettesbacktobasics.blogspot.com/2020/07/techniques-for-harvesting-quality.html
      Wij beiden wensen jullie veel success!


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