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Farm Design for Commercial Button Mushroom Cultivation

White button mushroom is a temperate mushroom requiring cooler climate for its growth. It is an indoor crop and is an ideal tool in
converting agricultural wastes in to proteinaceous food. In early days its cultivation was mainly confined to the hills. In the eighties
growers realized the potential of this crop and started its cultivation in the northern plains in the winter when the climate was suitable
for its growth. Many entrepreneurs in the plains further ventured and started its cultivation round the year by employing artificial
cooling facilities (chilling stations). Today its cultivation is done through out the country Some are doing it seasonally while many of
them have preferred to go for round the year cultivation. Today India boasts of having world�s biggest farm, the Agro Dutch Foods
Ltd, Lalru Punjab and many more environment controlled units exit in different parts of the country cultivating this mushroom round
the year.

Mushroom being an indoor crop does not require arable land, except for some nonagricultural land to build the infrastructure for
preparation of substrate, raising of crop preparation of spawn and postharvest handling. As mentioned above this mushroom is grown
seasonally and in environment controlled cropping houses and both require building of basic infrastructure. Seasonal growing is done
for 3-4 months when outside temperatures are favourable for the crop, i.e., during winter months in N.W. plains and from September
to April in the hills .

Seasonal cultivators of this mushroom are using traditional methods of its cultivation and are mainly cultivating this mushroom in the
thatched structures employing long method of composting. They usually take single crop in the entire season and are harvesting 12-15
kg mushrooms/ 100 kg compost. Environment controlled units are cultivating this mushroom round the year by having suitable
infrastructure at their disposal which includes a modern composting yard having bulk pasteurization facilities. Of late few of them
have shifted to indoor composting while new upcoming units have chosen to produce their compost entirely by indoor method.
Besides these facilities they are having insulated cropping rooms and other ancillary structures required for mushroom cultivation.
Few of the bigger units are having their own spawn lab and processing unit as well. An entrepreneur can start mushroom cultivation
modestly using seasonal growing houses and after gaining sufficient experience can shift to round the year cultivation employing
suitable climate control facilities. Suitable infrastructure including different machineries are required at the farm to carry out different
operations to govern the whole process of cultivation in such a fashion so that one gets optimum returns from his farm in this
competitive environment. The one who designs the farm in most scientific manner looking to the need of the crop and easy
accessibility to the different infrastructure for their operation convenience in less space, utilizing less money will gain handsome
returns in the years to come. Present chapter would deal in detail the infrastructure and machineries required for the seasonal and
environment controlled units.

A. Selection of Site and Pre-Requisites

Before selection of site, the following points have to be taken into consideration for greater operational efficiency and cost effective
production of mushrooms at the farm:

1. Chosen site should preferably be away from the municipal limits and entrepreneur should purchase sufficient land in one go
looking to the future expansion.

2. The site should be serviced by a motorable road, or nearer to a road head to reduce costs on transportation of raw materials to the
farm/finished product to the market.

3. Plentiful availability of water at the site either through a perennial source or should have sufficient underground water.

4. Easy availability of raw materials especially straw and poultry manure around the chosen site at cheaper rates in the area.

5. Availability of cheap labour in abundance.

6. Uninterrupted proper power supply at the chosen site.

7. Nearness to the market for the proper disposal of the produce.

B. Components of a Mushroom Farm

For round the year cultivation of this mushroom employing environment-controlled conditions a medium size plant would require
under mentioned components.

1. Spawn unit

For producing in-house spawn for self requirement and for sale to other units. This will have under mentioned major components.

a Cooking/autoclaving room: For boiling the grains and sterilization of the bottles/pp bags.

b Inoculation room: For inoculation of the sterilized bottles/ pp bags

c Incubation room: For incubating the inoculated bottles. Insulated and provided with AC.

d Cold Store: For storage of prepared spawn for its further disposal

Besides above some ancillary structures like office, small lab space, delivery area, etc. may also be required.
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Machineries required: Air conditioners, Laminar flow system, Autoclaves, BOD incubators, Boiler, Boling cattles, Refrigerators,
racks, pH meter, gas stoves, etc.

2. Composting unit

This will have under mentioned main components for production of compost

a Pre wetting area: For dumping of raw materials and their pre wetting (uncovered).

b Composting yard: For making piles out of the wetted materials (covered)

c Phase-I bunker: For phase -I composting (incase indoor composting is employed).

d Phase -II tunnels: For performing pasteurization and conditioning of the compost.

e Casing soil chambers: For pasteurization of the casing soil.

f Spawning area: For spawning of the prepared compost

Besides above certain ancillary rooms like boiler room, underground service room, store room, workers room, etc. would also be
required Machineries viz., boiler, blowers, air handling units, gratings, digital thermometers, compost retaining boards, ventilation
system for phase -I bunkers would be required by a medium size farm (up to 200 TPA). Large farm besides above may require a front
end loader (Bobcat) and other compost handling equipments including turner, filling line, etc.

3. Cropping unit

A cropping unit will have series of insulted rooms of designated size depending upon the production targets. Besides rooms there will
be AC/ compressor room, packing room, central corridor housing air handling units and pipelines.

Machineries required: Insulted doors, central chilling station (ammonia or freon based), air handling units, computer based controllers
(optional), racks, and trolleys, harvesting trays, etc. would also be required. For continuous electric supply to phase-I, phase- II
tunnels and cropping rooms, generators of desired capacity would also be needed.

4. Post harvest handling unit

It will have under mentioned components:

a Pre-cooling chamber (cold room): For storing the mushrooms before canning

b Canning hall: For housing the canning line for processing

c Laboratory: For quality control of processing

d Store: For housing the processed can

e Office: For sitting of the staff

f Machinery required: Canning line of desired capacity

5. General Layout/Location of various Units

The layout is so planned that all the infrastructures required to be built are accommodated in least possible land without over looking
mushroom cultivation requirements. The general layout of a mushroom farm has to be carefully planned after selection of the site,
keeping in view the several factors including accessibility of road to the composting yard as raw materials are to be dumped here for
their processing to the compost. Wind direction is also kept in mind for choosing the location of the composting facilities. During
most of the time of the year wind should flow from cropping area to the compost yard and not vice versa. Phase-I bunkers are
constructed in line nearer to the phase -II tunnels for their operational convenience and also to avoid heat losses. The bulk chambers
are built nearer to the phase-I bunkers. Both these structures are preferably built away form the road at the distant end of the yard so
that the distant end of the phase -II tunnels opens nearer to cropping rooms and away from composting yard (Fig. 8.1). The cropping
rooms are built away from composting area for reasons of cleanliness and avoiding contamination by pests and pathogens. The casing
pasteurization chamber is built nearer to the composting yard or within the composting yard with small platform for preparing the
casing soil (Fig. 8.1). Enough space for future expansion of composting yard, construction of more phase-I & II chambers and
growing rooms should be left vacant for planned development of a mushroom farm in a phased manner. Spawn unit is built far away
from the composting yard and nearer to the cropping area. Processing unit can be a separate entity or can also be built within the
building housing cropping rooms.

The foundation of the buildings is dug on the firm ground. The underground water pipes, electrical cables and sewers are laid well
before the actual construction starts. The entire site area should preferably be fenced or brick walled for security reasons. In areas
where land is scarce, double story cropping houses can be built to economize on space. The cropping rooms are generally built in
double rows with a path/gully in between for various operations and services.

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Fig 1. General layout of the farm

a. Composting unit

The components of composting unit will depend upon the method of compost production chosen. If one is going for indoor compost
production, in such a case requirement of composting yard will be greatly reduced and it will be 1/3 of the normal yard required when
one has chosen SMC. Now a days trend is for indoor compost production due to environment legislation. In such a case a small pre
wetting area, and small covered composting yard would be required with minimum of two-phase-I bunkers and one phase-II tunnel.
Size of all these structures would depend upon the production targets of the unit and size and numbers of the tunnels.

b. Prewetting area (PWA) (lagoon)

This area is constructed nearer to the road. It is a simple cemented structure having a saucer like depression in the center so that it
looks like a lagoon and water remain collected during the prewetting of the compost ingredients (Fig. 8.1). Center of the lagoon
should be around 1 ft deep. Excess water of the lagoon is collected in a goody pit built specially for the purpose at a convenient place
around PWA for its reuse. Floor of the PWA should be such that it can withstand the load of the front-end loader while performing the
wetting operations. It is usually not covered and is open to the sky. PWA terminates in the composting yard. Water connection with
2"-3" dia. pipe should be available in PWA permanently with additional portable hosepipe for use during pre-wetting. One dewatering
pump with a hose should be installed in the goody pit to pump out the run-off water for its reuse during pre-wetting. Water in the
goody pit may be aerated continously to avoid foul smell.

c. Composting yard

Fig. 2 Composting yard including Phase-I bunker

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The composting yard (Fig.2) is required for phase-I of composting. It is a prerequisite when one is going in for short method. The
composting yard should necessarily be a covered shed with 2-3 ft sidewalls on the two sides (length wise) where rain will not interfere
in the normal process of composting. The foundation of the composting yard should be laid on a firm ground and it should necessarily
be reinforced if mechanization of the composting yard has to be done as it has to withstand the load of heavy machines. The floor is
given a run-off of 1 cm per running meter away from the bulk chamber and towards the goody pit end.

The roof of the outdoor composting platform is built on tresses or RCC pillars 16 ft high with a GI or any other suitable
roofing. The covered The composting yard should be big enough to hold maximum compost stacks for phase-I of composting.
When adopting indoor compost production wetted ingredients are just made up into a heap for 3-4 days and do not require rick
formation in such a case a small platform can suffice the purpose.

Fig 3. Low cost composting yard

However, a large composting yard would be required if SMC is adopted. On an average one ton compost occupies about one meter
length of the composting yard, with an extra space of 2-3 m left on each side for turning with machines. Two bulk chambers will have
a platform with 10-15 m width. For two bulk chambers of 25 tons capacity each, a composting yard of 25 m x 13 m should be good
enough to concurrently run phase-I operation at a time for both the chambers. A drain should run on the two sides of the platform to
facilitate periodic cleaning. A few three phase 15 amp. power connection should also be provided at the composting yard for operating
machines like hopper regulator, compost turner, filling lines, etc. The yard should be well lighted with tube lights and strong
searchlights to facilitate round the clock operations at the composting yard

An overhead water tank is necessary, particularly where water is scarce, to store water for timely operations. The floor of the
composting yard for long method of composting should be simply cemented/brick layered with a low cost roofing of high-density
polythene fixed on iron tubular structure or it can also have thatched roof (Fig. 3). In practice (90%) of the farms cultivating this
mushroom seasonally are preparing their compost in the open fields and do not have any specially built composting yard built for the
purpose. However, such growers are facing lot of disease and pest problems. We recommend that the compost by long method by
seasonal growers should at least be prepared on a cemented platform- let it be open to the sky.

d. Phase-I tunnels (bunkers)

This facility is required when indoor composting is employed at the farm. These are specially built non-insulated tunnels having full
width opening at the front (Fig. 4). Dimension of the bunkers would depend upon the output of the compost required. Generally the
bunkers are 1.5 times more the size of the phase -II tunnels. It has a plenum (ventilation duct) constructed below the actual floor. A
perforated concrete floor having around 1 cm openings at a distance of 1ft each to the entire floor area is constructed above the
plenum or it has simple RCC /steel gratings having 20% opening to the entire surface area of the tunnel (Fig. 5) which is serviced by a
centrifugal fan having 1/4th the capacity of phase two blower which means that a ventilator having air displacement of 50 m3 per hour
ton of compost at 50 mm WG water pressure would suffice the purpose. A plenum floor involves pressurizing the entire airspace
beneath the concrete floor, allowing the air to move up into the substrate through the holes or through series of slates.

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Fig. 4. Bunker Fig. 5. Gratings over the plenum

Alternatively the bunkers have no plenum and several pipes (5-15 cm dia) are buried in the floor along the full length of the bunkers
having small holes (5-10 mm dia) at a distance of 15 to 30 cm each (Fig. 6). These pipes converge into a manifold, which in turn is
connected to a high-speed blower fan (around 1000 Pascal). A timer is usually attached to the blower, which pulsates the air in the
bunker periodically as per the setting of the timer. A minimum of 2 such phase-I tunnels (bunkers) are required.

Fig. 6. Bunker with aerated pipes

A bunker for 20-25 ton compost output at the time of spawning may have thedimensions 45 x 10 x 8 with 9 pipes of 2.5 m dia. at
distance of 1 ft. (6� from the wall). To equalise the pressure either the pore size may be increased or distance between the holes
may be gradually decreased from 1.5 ft. to 9�. These 9 pipes are linked to a bigger pipe of about 6� dia. which inturn is linked to
a centrifugal blower.

i. Pasteurization facility

A modern farm employing either indoor method or SMC essentially requires this facility. The bulk pasteurization chamber is
principally used for phase-II of composting for pasteurization and conditioning of the compost. For this purpose, an insulated chamber
is built with facility for steam injection and controlled recirculation and fresh air entry in the tunnel through a blower. The insulated
chamber is built with purpose of cutting off the external environment and simulating a desired environment inside for controlled
fermentation of the compost ingredients.

In Bulk pasteurization chamber compost is handled in bulk inside the tunnel or chamber and hence the name bulk chamber. The
compost after phase-I is filled into specially built chamber, which is properly insulated and provided with steam connection and air
blowing system for re-circulation. The compost is filled in the chamber on top of its grated floor built over the plenum. The plenum
has an air circulation duct used during pasteurization/conditioning (Fig. 7).

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Fig. 7. Cross-section of the bulk chamber (45� x 9� x 13�)

The bulk chamber should be constructed on one end, (away from road) of the composting platform. One end of the bulk chamber
should open into the platform and the distant end in the clean spawning area. The foundation of the bulk chamber should be dug on a
firm base ground. The floor must be laid with a good run-off provided with a drain to facilitate cleaning. It is pertinent here to note
that this floor is given a slope towards the service area end (blower end). A large tunnel will be around 90 cm deep towards the blower
end while it will be around 15 cm deep towards other end (filling end).

Floor should be properly insulated with thermocol/glass-wool 5 cm thick (15 kg/m2 density). The insulation is covered with isolating
membrane of PVC sheeting followed by 5 cm cement floor and finally the finish. Such floor is constructed for both cropping room
and the chamber. The walls should be 9" thick (one brick lengthwise) built over the concrete foundation. The length and breadth of the
bulk chamber will vary, depending upon the amount of compost to be treated in the chamber, with the height of 13 ft, the roof is made
of 4" thick RCC. The walls, ceiling and the floor below the plenum are insulated with 5 cm thick insulating material (15 kg/m2
density) necessary for effective insulating effect during pasteurization and conditioning of the compost. Required K value of the
insulating material should be around 0.5-0.6 kcal/ m2/h. Air leakage in bulk chamber must be prevented at any cost. The bulk
chamber has two floors one is real insulated floor while another false or grated floor, which is laid above the actual floor or plenum
over the ventilation duct. The grated floor must allow the air to pass through, for which approximately 25-30% of the floor area is left
in the form of gaps for ventilation/circulation of air and steam. The plenum is divided with a perforated brick wall (one or two) in the
centre for supporting the grated floor. The gratings can be made of wood (painted with bituminous paint), coated iron strips mounted
on angle iron frame or with concrete beams. Alternatively a concrete floor can be poured over the plenum as in case of phase -I
tunnels having openings. If nylon nets are to be used for mechanical filling and emptying, then cemented grated floor with appropriate
RCC strength is built specially for the purpose. The doors of the bulk chamber are made of angle iron or wooden frame with 2-3"
insulation in the middle and covered on both side with aluminum sheets, else they can also be made up of puff panels. The chamber
will have two exhaust vents, one for recirculation exit and the other for exhaust of gases on introduction of fresh air via dampers.

The steam line is also connected at the entry point of the blower. The walls and ceiling can be damp proofed by coating bituminous
paint on inside over the cemented surface, which will also serve as an effective vapour barrier. The grated floor inside and the work
floor outside should be of the same height for operational convenience especially when tunnel has to be filled mechanically.

Two types of tunnels (bulk chambers) are in use, two door bulk chambers and single door bulk chambers. In the single door bulk
chamber, the same door is used for filling and emptying and the other end is utilized for fixing installations (blower, etc.). In double
door bulk chamber, one door is used for filling (which opens into the composting yard) and the other for emptying (opening into the
sterile spawning area).

The bulk chamber can be filled/emptied manually or by conveyer belts. The uses of machines for filling/emptying are labour saving,
time saving and ensure homogenous filling as well as maintenance of absolute cleanliness during operations. For mechanical
emptying two nylon nets are used, one fixed over the RCC grated floor (gliding net) and the other moving over the lower net (pulling
net). The compost when brought out is fed into the spawn-dosing machine where requisite amount of spawn is mixed with the
compost and the seeded compost is then poured into clean polythene bags for transport to the growing rooms.

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The dimension of the tunnel for producing 20-25 ton of compost are 36� x 9� x 13�. One may replace the plenum with plastic
pipes fitted with spigots (Fig..8). The centrifugal fan can be placed at the bottom as well as on the roof (Fig. 9) depending upon the
space and design.

Fig. 8. Plastic pipes ready for spigot fitting Fig. 9. Line drawing of Phase-II tunnel for 20-22 ton compost
output
(Source: http://www.21food.com/) (Source: http://www.agaricus.ru )

e. Air handling units of the tunnel (AHU)

For effective pasteurization and conditioning of the compost in the tunnel specific requirements of air and ventilation are to be met,
which are generally met by providing/installing AHU in the tunnels (Fig. 10). Effective pasteurization and conditioning is attained
when 150-200 m3 air per ton of compost per hour is blown through the compost mass. For this purpose high speed centrifugal fan is
chosen and is placed on the slope end of the ventilation duct in the underground service area. Compost is spread over the plenum on
the grated floor in about 2-2.2 meter thick layers. Nylon nets are generally placed under the compost if mechanization is necessary.
These together give a resistance of around 60-65 mm WG during pasteurization taking together the resistance of the air ducts, the in
and out openings, the perforated floor, etc. the static pressure of the blower fan should be around 100 mm WG at 150-200 m3 air per
ton of compost per hour. Blower fan must be well protected internally and should be made up of sheet steel. Aluminum is ideal for air
ducts and should at least be 2 mm thick and there should not be any leakage in the duct system. Ducts are generally insulated with
glass wool or any other suitable material. Fresh air is regularly required in the tunnels and since this air is drawn from the open
atmosphere, chances of fungal spore�s contamination are likely and hence the incoming air in the ventilation duct should be filtered
and should pass through 2 mm fungal spore filters. The pre filters and filters should be washed at regular intervals. The inlet and
exhaust openings must be fitted with a flap valve, which opens only when positive pressure is created inside the tunnel. The
dimensions of inlet and exhaust openings should be the same.

Since, India is a tropical country where temperature during summer months goes above 45�C. Cooling of compost for spawning
during this period becomes difficult by simple introduction of fresh air. Special cooling arrangements are therefore required to be
made in the AHU of the tunnel for this purpose. A ten ton capacity cooling equipment or cooling coils from the central chilling plant
is installed at the top of the AHU or such coils can be fitted in the blower section of the AHU. This arrangement is very effective in
cooling of the compost in tropical areas during summer months. Installation of such facilities however requires heavy investment.
Compost during these months can satisfactorily be cooled during nights when the temperature is low.

f. Casing pasteurization chamber

Casing pasteurization chamber is just a mini bulk chamber. It has all the necessary components as required for the tunnel. Only
difference is that the plenum is not having any slope and capacity of the blower for proper steam injection and its uniform distribution
inside the casing mass is around 1/4 the capacity of the tunnel (Fig. 11). The size of the chamber will depend upon the size of the
compost chamber and the size of the growing rooms. One chamber load should provide casing for one compost lot from each tunnel.

The casing inside the chamber can be treated in the bulk and in such case it is filled up to the height of 90 cm only as against the
tunnel where compost is filled upto the height of 2-2.2 meters. Else casing after wetting is filled into the perforated wooden/aluminum
trays which are stacked one over the other inside the chamber and steam treated at 65�C for 6-8 hours. This chamber can be built
near to the composting yard or within the composting yard with a separate casing mixing platform.

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Fig. 10. Tunnel with air handling unit Fig. 11. Casing pasteurization chamber

g. Spawn unit

The layout plan of a spawn laboratory is given in Fig. 12. A total built in area of 60� x 30� x 12� should be good enough to
house the entire spawn unit. This area will be divided into different work areas like boiling/autoclaving room, inoculation room,
incubation room (insulated and with AC), cold room (heavily insulated with chilling facilities), store, office and delivery area.

h. Cropping unit

Since mushrooms are grown indoors under simulated environment specially created for mushroom growth, the cropping rooms are
required to be built specially for the purpose Two types of cropping rooms are built suiting to particular requirement - those required
for seasonal growing and those for environment controlled growing round the year (Fig. 13).

Fig. 12. Layout of plant of a spawn lab

Seasonal cropping rooms: Seasonal cropping rooms are simple rooms with modifications for maintaining various growth
parameters. These cropping rooms will have a cemented floor, cemented walls, cemented ceiling or a false ceiling with arrangement
for forced air circulation inside. The seasonal cropping rooms are built of simple brick walls with roof made of asbestos sheets and a
false ceiling. The room is more or less made air tight to make the air handling system work effectively for obtaining necessary air
changes during growing. No insulation is required for seasonal growing rooms, as it will not allow heat dissipation from the room
efficiently. These simple rooms are used for seasonal mushroom growing, coinciding various phases of growth with prevailing outside
temperatures. No energy is generally used for heating/cooling of the rooms under seasonal growing conditions. However few units in
plains have installed heavy-duty coolers to bring down the temperature in summer conditions. The cropping rooms for seasonal
growing can also be made with a thatched roof and a false polythene ceiling. The door is installed on one end and the exhaust vents on
the opposite end of the door (Fig. 14). The mushrooms are grown on beds made out of bamboo sticks and sarkanda stems (a plant

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abundantly growing as a weed in North western plains of India). These growing rooms can also be built as low cost structure, steel
pipe frame with highdensity polythene covering from outside. The real low cost growing houses built in rural areas are made of walls,
roof and door of sarkanda.

Fig .13. Cropping section of the mushroom unit Fig. 14. Cropping section of the
mushroom unit
The mushroom houses made with bamboo frame and synthetic fiber cloth material, both inside and outside, with paddy straw
insulation in between has also given good results under hill conditions for seasonal growing.

. Environment controlled cropping rooms

i

The environment controlled cropping rooms are built like hermetically sealed chambers where the air movement is controlled either
manually or semi automatically with mechanical control systems. These cropping rooms are appropriately insulated and the
dimensions of a cropping room are determined by the amount of compost to be filled into the room. Rooms with greater length and
narrower width gives better results as far as air handling inside the room is concerned. A cropping room, with a capacity to take
compost from one bulk chamber, is considered advantageous as one bulk chamber load can straightaway be filled into one cropping
room. Further, cropping cycles to be taken will determine the numbers of growing rooms in the unit. Now a days 60 days cropping
cycle is generally taken and in this manner a minimum of six crops are taken / room in a year. In such conditions a minimum of 12
rooms are required to have constant supply of mushrooms from the unit round the year. In this case every room is filled with the
spawned compost every after 5 days. Both bulk chamber and cropping rooms of 20-25 tons compost capacity are considered to be
operationally efficient, as the filling/emptying operation and spawning can conveniently be done in one day when machines are not to
be used. However, bigger units may have the growing rooms handling compost to the tune of 60 tons or more. Growing rooms are
such designed that maximum compost can be accommodated in least possible area without over looking to the mushroom growing
requirements. To give an example a room size of 60 x 17x 13 ft can easily accommodate 20-25 tons of compost when cultivation is
done in shelves or bags. The foundation of growing rooms should be laid on dry and firm ground. The floor is laid as explained for
bulk chamber. The walls will be made of one brick thickness (9"thickness) and ceiling made of 4" thick RCC. The growing rooms will
have a single insulated door and 2 vents for exhaust on the back wall 2-3 ft above ground level. One opening is provided on top of the
door for entry of the Air Handling Unit (AHU) delivery duct or for fresh air intake inside the room through AHU. The walls, ceiling
and floor should be insulated with 5 cm thick insulating material. The room should be made airtight and all leaks closed to prevent
ingress of heat from outside. The cooling, heating and forced air circulation in the growing room is done via AHU installed for each
cropping room individually. The floor and walls of the cropping rooms should have a smooth finish.

j. Structural details special to cropping rooms

i. Floor

The floor must be well laid out and should be strong enough to take the heavy load of metal racks to be kept inside for growing
mushrooms. The floor should be insulated with insulating material 5 cm thick (sheets of thermocol or glass wool or polyurethane).
The insulation should be protected by a PVC sheeting, below and above, against moisture. It is then covered with wire mesh and
finally 5 cm thick concrete floor is laid on top, which is given a smooth finish. The floor should have slight slope towards the entry
point for discharge of cleaning water and placement of formalin trough for foot wash. The trough is connected near the wall to an
exhaust drain to carry washings from the room. The water discharge hole is protected at this point to prevent leakage of air from the
growing room. PUF pads can also be used specially in place of wall between rooms.

ii. Walls

The walls are made of brick 22.5 cm thick, which are given a smooth finish with cemented plaster. The insulation sheets are fixed on
the walls (5 cm thick thermocol, glass wool/polyurethane), with the use of hot coal tar. Holes are drilled on four corners of the
sheet/inside the cement wall for expansion fasteners which are fixed by screwing in the nail with 4"-5" long steel wire tied on its head.
The wire hangs out of the sheet to be used for tightening of wire net fixed on top of the insulation. The layer of cement plaster is then
applied (2 cm) on top of this and given a smooth finish. Bituminous paint is applied on cement plaster as a vapour barrier. The
painting can be avoided in cropping rooms if the cook out is not done by steam. This wall will be good enough to give a Kvalue of
0.5-0.6 kcal/m2h, even lesser and will facilitate proper control of climate inside the cropping room.

iii. Roofs

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The roof is made of RCC (1 : 2 : 4) 12-15 cm thick. The inside is given a cement plaster finish for application of insulation (as
explained for the wall). The roof on the outside is protected by tarring it on top, followed by 10 cm thick loose soil, 5 cm thick mud
capping and finally the tiles. This will protect the roof from weathering effects of rain and will ensure longer life of insulation and
prevent seepage of moisture into the room in rainy season. In hilly areas with a high rainfall index, slanting GI sheet roof over the
insulated RCC roof will be excellent and in that case mud capping/tiling of the roof is not required.

iv. Doors/vents

The doors of the bulk chamber and the cropping room are made of wood or angle iron frame covered on inside and outside with
aluminum sheets/GI sheets with insulation of 5-7 cm in the middle. The doors will have a rubber gasket lined on inner periphery so
that the door becomes air tight when closed. The door will operate on hinges, with a strong locking latch for opening and closing of
the door. The exhaust vents are fitted with wire net, louvers and insulated lids. The louvers allow the CO2 laden air to exhaust under
positive pressure created by the blower inside the air handling unit.

v. Lighting arrangement

There should be a provision for tube lights and a mobile strong light for inspection in each cropping room. The tube lights should be
protected with water proof housing. The tube lights should be fitted on all the walls vertically at various heights to facilitate lighting
of all beds. There should be provision for a few electric points (5 and 15 Amp.) for operation of water spraying equipment and CO2
measuring instruments.

vi. Water connection and sewers

One clean water pipe line (1" or 1.25") with tullu pump installed to it for delivering clean water for spraying should be provided in
each room. Underground drainage line for carrying the washings from the room and wash basin discharge should be laid before
construction of the building. This waste water line should be connected to the common sewer. In H.D. polythene cropping rooms,
sunkun traps on the floor for fresh water and drainage water are provided inside the growing house with each trap of 1� x 1� x
1� dimension fitted with an iron lid on top. It is desirable to lay underground drainage in the central gallery in advance of erecting
the structure for carrying away the waste water/washings from the cropping rooms.

vii. Gallery

The gallery between the rows of cropping rooms should be wide, (12-15 ft) to allow efficient performance of various operations. The
height of the gallery should be same as for the growing rooms alternatively it may be about 8' with a false ceiling, leaving another 5 ft
above for pipeline and space for AHUs.

viii. Racks

Racks are made up of the angle iron for horizontal and vertical support with iron mesh strips used for the shelves for housing compost.
Length (vertical axis) of the racks is generally made up of 5 cm thick angle while horizontal support is made up of 3.5-4 cm thick.
Width of the each shelf on the racks should not be more than 135 cm in any case as width more than that creates hindrance in
performing various operations during cropping and most important of that is harvesting. Cultivation can be done in bags or in shelved
beds. Five to seven rows of shelves (depending on height of the room) can be provided one above the other in the racks keeping a
minimum distance of 60 cm in between. This distance can slightly be narrowed down if cultivation is employed in shelved beds. In
such a case all the four sides of the shelf should be provided with 15- 20 cm high iron sheets for housing the compost in the beds. If
more than 5 shelves on each rack are kept in the room than there should be provision of trolley running in between two rows of racks
just above the fourth shelf for carrying out the various operations. Depth of the compost in shelves is generally kept at 15-20 cm while
bags can be filled up to the maximum height of 30 cm. A room of standard size (60 x 17 x 12 ft) can accommodate 2 rows of racks
each 4.5 ft. (135 cm wide). This will absorb 9 ft (270 cm) of the room and the rest 8ft can be used to have one central path of 3 ft. and
2 side paths of 2.5 ft. Length of each rack would be 52-55 ft.

ix. Air Handling Unit

This unit is employed for creating proper weather inside the growing room specific to white button mushroom. Air handling unit is
generally installed in each room at the top of the door, which is made up of aluminium or G.I. Sheets. In certain cases it can also be
placed on the top of the floor of the growing room or in the corridor. Indirect cooling of air through chilled water (5-60C) is generally
employed in mushroom cultivation. Mushroom generally require 225 m3 of air per hour per ton of compost. To meet this requirement
a high speed centrifugal fan of required capacity having working pressure around 50 mm WG is generally mounted in the body of
AHU (Fig. 15). Alternatively if the capacity of the growing room is to accommodate around 20-25 tons of compost, then a fresh air
fan of 600 mm dia of low pressure can also be chosen for this purpose, but in such case a booster fan of 375 mm dia will also required
to be mounted in AHU for extracting fresh air from outside (Fig. 16). In AHU cooling coils, humidifiers, heaters, eliminators and
other components of AHU are mounted on the back of the supply air fan. Cooling coils are generally connected to the chilling unit via
insulated ducts, which supply chilled water at 5-60C to these coils. This water is generally chilled in an insulated tank or by cooling
unit comprising of a compressor, condenser, evaporator and a cooling tower. Heating unit of AHU can employ strip heaters or steam
through a low-pressure boiler. Humidifiers can use free steam

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Fig .15. Mdoified AHU with fresh air fans Fig. 16. A standard AHU with centrifugal blower and ducts inside the
growing room

from the boiler to generate required humidity in combination with air pressure or can employ fine jets, which produce fine mist of
water in the humidifier section of the AHU. PVC eliminators, eliminate the free water going inside the growing room. Booster fan in
combination with supply air fan supplies fresh air inside the AHU through fresh air dampers. Since fresh air coming from outside
atmosphere may contain fungal spores, which may contaminate the crop, this air is generally passed through pre filters and a HDPE
micro filter section (2-5 um). The AHU has a mixing chamber with recycling dampers, which can regulate supply of fresh air or room
air inside the growing room. Out let of the AHU is connected to the distribution duct in the growing room, which is generally made up
of PVC sheeting having its end month closed. It hangs below the ceiling in the central corridor of the room. This duct has ports (5 cm
dia) facing downward at a distance of around 50 cm each. When the air is blown inside the room via AHU a positive pressure is
created and CO2 laden air of the growing room is expelled in the atmosphere through an outlet. In such cases back vents are not
provided in the growing rooms. Alternatively AHU can be so fabricated having provision to exhaust CO2 laden air of the growing
room in the atmosphere through an out let. In such cases back vents are not provided in the growing rooms Central cooling unit can
employ ammonia, freon or vapour absorption machine (VAM) for cooling purpose. If size and capacity of growing unit is small, say
250 MT per annum employing around 12 rooms then cooling employing evaporator, inside the AHU can also be chosen. In such a
case each AHU will be a self contended cooling unit,

Fig..17. An automatic canning line

employing, compressor, condenser and an evaporator. This unit will also have heating and humidifying arrangements.

k. Processing unit

Design of the processing unit with its various components is given in the Fig..17 & 18. Utmost strict hygienic conditions are required
to be maintained in the canning hall and hence special care has to be given at this front while designing/ constructing canning unit.
The floor must be well laid off preferably having kota stone having slope at one end. Walls should have ceramic tiles up to the height
of 5-6 ft. Height of the canning hall should be not less than 14 ft in any case. Surrounding where this facility is built should be clean
and away from the composting yard. Floor of the canning hall should have enough strength to support the weight of different utilities
to be installed required for the canning operation. Canning hall should be big enough looking to the future requirements or processing
of other items. All the doors and windows should have wire mesh shutters to prevent the entry of insects and flies. Three-four exhaust
fans should be installed in the hall at the appropriate places.

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Cold room should be properly insulated with minimum of 10 cms insulating material and separate product cooler of required tonnage
should be installed to it. FPO license is required for processing purpose.

Fig. 18. Design of a canning unit

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