Grain Storage techniques

1. Recent Advances in Grain Processing-
Storage and Handling of Food Grains
A. Poshadri
Reg.No: 2020T01P

2. Introduction
• Grains are one of the major food staples in the world. Rice, wheat, and
maize offer 60% of the food related energy input around the world.
• India produced 297.5 MMT of Food Grains (comprising wheat, rice,
pulses and coarse cereals) during 2019-20.
• Storage is an interim and a repeated phase during transit of agricultural
products from producer to processor and its products from processor to
consumer.
• Storage of grain and control of quality occur in three locations;
 on the farm,
 collection points serving a number of farms, and
 terminal points where grain is processed or moved forward in
larger bulks.

3. • All farmers store food grains for their own use as seeds or food.
• Quantity stored for the above purposes varies between 22 and 71 % of the total
production.
• Conventional storage methods employed for storage of grains, seem to be
totally inadequate for the preservation of the quality and prevention of their
wastage.
• Improper post harvest handling of grains is responsible for losses in the grains to
an extent of about 7%,
• Total 12 to 16 million metric tons of food grains were spoiled due to
unavailability of proper post-harvest handling of grains every year.
• Sufficient to feed the 33% population of India and total yearly grain losses has
been estimated near about INR 50,000 crores.

4. Need of Storage
• Feeding ever growing human population
• Fluctuation in price and market demand or shortage and famines
• Agricultural products need to stored for season to season and year to year
demand
• Off season requirements i.e., potatoes, onion, fruits etc.
• When a bumper production of particular commodity then storage is required
• Pilling/ provision for large scale processing
• Prevention of original varieties from extinction (Germ Bank)
• Preservation of nutritional quality

5. For best storage performance
• The produce must be thoroughly cleaned and graded,
• Dried to the safe storage moisture level of 10-12 % for food grains and 7-9%
for oil seeds (on wet basis) for a safe storage period of 6-12 months.
• Storage structures should to be properly repaired, cleaned and disinfected,
• Structures should bear the load of grain stored and do not permit
contact/exchange with outside humid air,
• Structures should be constructed in the coolest part of the house/ farm.

6. An ideal storage facility should satisfy the following requirements
• It should provide maximum possible protection from ground moisture, rain,
insect pests, moulds, rodents, birds, fore etc.,
• It should provide the necessary facility for inspection, disinfection, loading,
unloading, cleaning and reconditioning.
• It should protect grain from excessive moisture and temperature favourable
to both insect and mould development,
• It should be economical and suitable for particular situation

7. Food grain storage structures: recent trends
• Storage structures are playing key role to prevents the losses and keep the
grain safe during storage by minimizing the effect of rodents, microorganism
and environmental factors to feed the growing population of the world.
• Huge amount of grain up to long duration many modern grain storage
structures has been introduced which is generally used by different grain
processing industries, FCI, Grain mills and whole sellers.
• Advanced storage structures like ware house, silo, bin, cold storage, hermetic
storage system and controlled atmospheric storage system were used for
storing the food grain according to availability, suitability and acceptability for
particular types of food grains, durability of storage and place of storage.
• The storage structures like Pusa bin, PAU bin and Hapur tekka has been used
for small quantity storage

8. PUSA BIN - low density polyethylene” storage structure
• Consist of the floor and lower part of the walls
burnt with a layer of plastic sheeting inserted
between two bricklayers.
• This protects the grain from moisture and
prevents air from entering.
• A separate tached rook around on top provides
protection from sun and rain.
• The other design of Pusa bin is made of double
walls of masonary each 4.5 inch thick with
polythene sheeting in between.
• The outer layers have steel reinforcement and the
sides are plastered with cement.

9. PAU Bin
• Punjab agricultural university has been designed a storage structure called as
PAU bin, constructed with galvanized iron sheet.
• Capacity varies between 1.5 to 15 quintals depends upon the size of designed
PAU bin.

10. Hapur Tekka
• It is cylindrical in shape, locally constructed
on base of metal tube with the help of
bamboo and expandable clothes and
another hand in improved structure,
bamboos has been replaced with galvanized
iron or aluminum sheets for getting more
durable structure.
• Grain has been taken out with the small
circular or rectangular outlet provided in
the bottom of the structure
• Generally Hapur tekka can contain grains of
2 to 10 tons

11. Commercial grain storage structures
Covered storage
• The most popular storage system in India followed by the FCI, Central and
State Warehousing Corporations (CWC and SWC) is bag (jute bags) storage in
warehouses.
• The grain is packed in jute bags and stacked inside covered structures called
warehouses / godowns.
• The godowns are conventional masonry structures constructed on a raised
platform as per approved design and specifications of the Bureau of Indian
Standards

13. New trends in covered storage
• CAP Storage (Cover and Plinth) is a term given to storage of food grains in the
open with adequate precautions such as rat and damp proof plinths, use of
Dunnage and covering of stacks with specially fabricated polythene covers etc.
• The construction of brick pillars to a height of 14" from the ground, with grooves
into which wooden crates are fixed for the stacking of bags of food grains.
• The stacks are covered with 250 micron LDPE sheets from the top and all four
sides.
• Food grains such as wheat, maize, gram, paddy, and sorghum are generally
stored in CAP (cover and plinth) storage for 6-12 month periods.
• It is the most economical storage structure and is being widely used by the FCI
for bagged grains.
• These structures can be fabricated in less than 3 weeks.

15. Quality control during CAP storage of food grains
• Covered storage structures may be constructed as per approved specifications.
• Adopt scientific code of practices for storage of food grains
• Adequate dunnage materials, such as wooden crates, bamboo mats, polythene
sheets may be used to check the migration of moisture from the floor.
• Fumigation covers, nylon ropes, nets and insecticides for control of stored grain
insect pests may be provided in all the godowns.
• Prophylactic (spraying of insecticides) and curative treatments (fumigation) may
be carried out regularly and timely for the control of stored grain insect pests.
• The prophylactic treatment involves the use of pesticides like malathion (50%
ec), DDVP (76% ec) and deltamethrin (2.5% wp).
• Curative treatment involves use of fumigants to control infested stock or
godown in airtight condition.

16. Quality control during CAP storage of food grains
• Effective rat control measures, both in covered godowns as well as in CAP
storage may be used.
• Food grains in CAP storage may be stored on elevated plinths and wooden crates
used as dunnage material. Stacks are properly covered with specifically
fabricated low-density black polythene water-proof covers and tied with nylon
ropes/ nets.
• Regular periodic inspections of the stocks/ godowns may be undertaken by
qualified and trained staff.
• The principle of First in First Out (FIFO) may be followed to the extent possible,
so as to avoid longer storage of food grains in godowns.
• Only covered wagons may be used for movement of food grains, so as to avoid
damages during transit.

17. BULK STORAGE
• Processing industries are more inclined in favour of bulk storage structures for
food grains, as the operations such as loading/unloading, fumigation and aeration
of grain bulk can be mechanized.
• Bulk storages used by rice mills, oil milling units, roller flour mills store grain to
meet their processing requirements.
• There are two types of silos on the basis of design: hopper bottom silos and flat
bottom silos.
• The capacity of hopper bottom silos range from 10 to 1,500 tonnes, whereas flat
bottom silos are made to store up to 15,000 tonnes of grain.
• The galvanized iron corrugated (GIC) silos are quite popular in India among
industries.

18. Silos
• Silos are constructed either with metal or concrete but according to the
economical point of view metal silos are better than the concrete silos.
• Capacity of the silos depends upon the diameter and height of the silos.
• Approximately 25 thousand tons of food grain can be stored in this storage
structure and loading and unloading in the case of huge silos performed with
the help of elevators and conveyor.
• Silos are generally constructed with metals, aluminum, concrete and rubbers
used for long term storage of bulk quantity of food grains.
• Silo or bins are cylindrical in middle and top portion is conical in which augur
rotates for aerate the grains and prevents the chance of hot spot creation.
• Cone-bottom silos are easier to clean than flat-bottom silos due to their self-
emptying design, but are limited to capacities less than 300t.

22. • Warehouse constructed with bricks, concrete-cement and metals and height of
foundation floor always kept nearly 0.45 to 1 meter from ground level which
prevents the frequent entry of rodents.
• Within the structure, wooden pallets are used for stalking the sacks of grains
which prevent the moisture migration from floor to food grain.
• Adequate facilities of protection like proper sealing of the doors, maintenance
of inspection doors, and ventilation controlled, etc. has been very necessary.
• Proper stack formation with maintaining the standard distance between two
consecutive stacks (nearly 1.7 meter3 for 1 ton of food grains) is important for
easy handling operations.

23. • Damp proof floor construction
• 15 cm thick layer of gravel and sand well rammed at the bottom
• 12.5 cm thick layer of stone or brick ballast or double layer of brick
• 10 cm thick layer of cement concrete (1:4:8)
• 1.25 cm thick bitumen mixed with sand
• 4 cm thick layer of cement concrete (1:2:4)
• 2.5 cm thick layer of cement concrete (1: 1 1/2: 3)
• The walls are made of bricks or stone laid either in lime mortar (1:2), cement
mortar (1:6)
• Thickness of the wall is either 37.5 or 45 cm
• The height of the walls on which trusses are kept: 5.5 m

24. • Roof construction
• Either gabled or flat roof
• Gabled roof is covered with
corrugated sheet
• Flat roof is more durable – either
reinforced brick or concrete – 10 to
12.5 cm thick
• The terracing on the roof is made of
brick ballast, surkhi, and lime ( 3.5:
1:1)

26. Hermetic Storage
• Oxygen level was lowered down up to 1–2% due increasing the carbon dioxide
level or creating vacuum.
• Large hermetic storage called as Bunkers commonly used from last decades of
20th century and constructed with different capacity range from 10 -30
thousand tons.
• Researchers stated that hermetic bunkers have been suitable for storing the
wheat of 12.5% moisture content for four years without any qualitative
degradation.
• Hermetic storage structures are frequently used for storing the food grains and
provide easy portability, avoid the insect-pest infestation and retain the
qualitative characteristics during storage period.

27. • Hermetic storage containers are very efficient to protect the food grain and
reduces the losses up to 0.15% as well as increased the shelf life with the
destruction of mould and other micro-organism (up to 99.9%).
• Construction of hermetic storage structures:
0.59–1 tons known as Super grain bags
5–30 thousand tons grains - bunkers and Cocoons.

29. Grain Bunker
• Grain Bunker is world’s most cost-effective scientific solution to store grain for a
short to medium duration.
• Capacity of a Grain Bunker may range from as small as 500 MTs to as big as
30,000MTs each.
• Grain bunkers are designed to put an end to the traditional skyscraper grain silos
and are fast gaining popularity amongst grain handlers who are looking for
sturdy, flexible, cost effective but scientific method of grain storage.
• Geometrically Grain Bunkers are like Cover & Plinth (CAP) Storages of India with
a difference that, CAP stores grain in bagged form on the ground whereas Grain
Bunker in bulk form.

30. Grain Bunker Construction
• It consist of modular components inclined corrugated steel walls of approximately
0.5 to 1.5 Mtrs in height, supported with steel support members.
• It is constructed over a compacted earth pad with rainwater drainage slope so as
to save grain pile from getting wet.
• The floor area of the storage space is covered by durable plastic sheet and the
stored grain then covered with a rodent proof, UV resistant, and waterproof
tarpaulin.
• Covering tarpaulin is tightly sealed to protect the grain from pests and weather, as
well as to allow for effective fumigation.
• Grain Bunkers are equipped with Aeration System with Axial and centrifugal fans,
to expel the moisture, dust, and foul smell from the grain pile.
• Aeration can be used for in-store drying or in-store hydrating of grains.
Fumigation systems too are installed to prevent grain from infestation.

32. Facilities where bunkers can provide rapid, convenient, and inexpensive
solutions are:
• At grain silo terminals when silos are filled to the capacity and additional
storage space is required to occupy surplus grains during bumper crop
situations.
• At rice mills, flour mills or dal mills where most of the grain is milled within 6
months.
• At mandis to avoid bagged storage and to make system fast and effective.
• At farms or collection center where grain is to be held on a temporary basis in
anticipation of higher prices.
• As buffer stocks for food security under emergency situations.

33. Problem in bag and bulk storage and their control
Two methods of grain storage
1. Bag storage
2. Loose in bulk storage
The choice based on the local factors
• Type of grain
• Duration of storage
• Value of grain
• Climate
• Transport system
• Cost and availability of labour
• Cost and availability of bags
• Incidents of rodents and certain types of insects

36. Grain Handling
• Grain handling and conveyor systems should be designed to minimise damage to
grain.
• Pulses are more susceptible to impact damage than cereals and should not be
moved in pneumatic grain conveyors, as the impact speed of grain is higher than
the critical 12m/s.
• Augers smaller than 125mm in diameter should also be avoided with pulses.
• Augers should be run full, and preferably slowly, to reduce grain damage.
• It is easier to modulate auger speed if driven by petrol/diesel engines, than by
electric motors.

38. Grain receivable hoppers
• A high capacity receival system is needed for
efficient transfer of grain from trucks, or tractors
and trailers.
• Ideally, it should be possible to deposit a trailer
load and pull away from the unloading area within
minutes.
• An in ground receival hopper is typically fitted
with a screw conveyor, or auger, to raise grain for
conditioning or storage.

39. Grain conditioning and metal detection
• Foreign materials and dust must be removed to eliminate problems further
down the grain storage and handling system.
• A grain conditioner, or scalper, removes foreign particles, weed seeds, small
size grain, straw and husk.
• A dust extraction and collection system prevents dust entering the
environment.
• All foreign metal objects must be detected and removed before they can cause
damage.
• A permanent - or electro -magnet can be located in the chute that feeds the
grain conditioner, but needs to be checked and cleaned regularly.

41. Belt and bucket elevators
• Bucket elevators are used mainly to lift grain vertically to silos or other storages.
• Deliver the grain directly into silos using diverters that direct grain into a gravity
chute to the selected silo, or by using belted conveyors to transfer grain
horizontally to the various silos.
• A flat belt between crowned pulleys at the top and bottom of the casing has
small buckets attached at regular intervals to carry the grain from the elevator
bottom to the top.
• The capacity depends on the volume of the buckets, the spacing and the speed
of the belt.
• Bucket elevators are self-cleaning by design and are typically fixed in position.

43. Auger (screw conveyors)
• Auger elevators are one of the cheapest methods of elevating grain and can be
fixed or portable.
• These are available in a wide range of lengths and capacities and are usually
powered by an electric motor.
• They are comparatively light in weight, dependable in operation and popular
due to good portability.
• Long augers may be mounted on wheels for easy transport.
• The angle of operation is adjustable, but the capacity declines as the auger is
raised.
• High moisture content in grain also reduces the capacity of the auger.
• Old augers with worn flighting can damage split-prone grain.

45. Belt conveyors
• Belt conveyors are typically used
to transfer grain horizontally.
• Inclines up to 15° are possible -
and even up to 30° with ribs
fitted to the belt.
• Belt conveyor capacity is high and
grain can be loaded or unloaded
anywhere along the belt.
• Belt conveyors do not damage
the grain and raise little dust.

46. Drag chain conveyor
• Drag chain conveyors, or paddle conveyors, use a series of paddles fixed to a
loop of chain moving inside a fully enclosed conduit.
• The circular paddles are sized to fit snuggly in the conduit.
• This fully enclosed system prevents dust in a building or other space
• Drag chains can move grain at any angle, including horizontal, and are largely
self-cleaning, although corners of the chain loop will typically require attention.
• Drag chain conveyors are a permanent installation, but can be easily extended
for facility expansion.

48. FACTORS INFLUENCING SAFE STORAGE

50. • The storage life of grains depends mainly on two physical factors: temperature
and moisture content
• Stored-product insects can live at temperatures from 8°C to 41°C and RH 1 to
99% and development and multiplication are optimum near 30°C and 50–70%
RH. but stop at 18°C.
• Mites can live at temperatures from 3°C to 41°C and RH from 42 to 99% with
the optimum for development and multiplication near 25°C and 70–90% RH.
• Fungi can develop at temperatures from 2°C to 55°C and R.H from 70 to 90%
with the optimum temperature near 30°C, and RH around 80%.

51. • Effect of micro-organism and insects-pest can be controlled up to certain extent
with development of adequate condition within the storage structures and
most suitable temperature was considered 21°C and moisture level nearly 9%
within the bin.