Using local containers
Hermetic storage or sealed storage involves enclosing the grains in an air-tight container that minimizes gas exchange from the surrounding air with the inter-granular atmosphere inside the container. Benefits of hermetic storage include insect control without pesticides, high germination rates of seeds even after one year of storage and high milling quality.
Why use locally available containers?
There are commercial hermetic storage products like the Cocoons™ and the IRRI Super bags. However, in rural settings there are often no supply chains yet allowing farmers access to these commercial solutions. In local markets there are often containers available that can be easily converted into a hermetic storage system and thus allowing farmers to benefit from hermetic storage even if they can not buy the commercial solutions yet.
Examples of hermetic storage using local containers
On principle any solid container that can be sealed air tight can be used. If the material is porous like that of a clay pot it needs to be sealed e.g. using latex paint in the inside and the outside.
CAUTION: Plastic film (plastic bags) are very thin and have high oxygen permeability. Normal plastic bags, e.g. polyethylene bags (PE bags, polybags) that can be bought for various purposes let too much oxygen pass through the material. They are therefore not hermetic in the sense of hermetic storage. The IRRI Super bag is made from a special plastic composition that minimizes the oxygen permeability.
How to store your grain hermetically using local containers
Make sure to follow the steps below. If you use a container that contained chemicals or oil before clean it thoroughly. Make sure that the container does not have any holes or cracks.
- Clean the seed or grain and dry to the correct moisture content. (seed 12%, grain 14%).
- Place seed or grain in the clean container.
- Fill the container completely with seeds to avoid dead air space, the more air is inside the slower the oxygen drops.
- Seal the container air tight:
- When using a container with a screw top or press fitted closer use grease or silicon to seal the opening.
- When using clay pots or vessels made from porous material, paint inside and outside of the container with latex paint.
- Store the containers either undercover or in the shade.
- Keep the container closed until you need to use the grain/seeds. Use it all at once.
While the technology is simple users sometimes still have bad experiences when the oxygen levels are higher than expected. This is often due to poor management. The following points are important.
Intermittent opening and closing allows oxygen re-entry which can lead to the rapid re-infestation of insects that hatch from eggs or larvae.
In containers that are only partially filled, the large air space to grain ratio may not allow oxygen levels to reduce to a level that will control insects
Comparison of commercial and locally available containers
There is no ideal solution since both systems have disadvantages. The choice of a hermetic storage system depends on availability and local conditions. The table below compares both systems.
|Commercial hermetic storage systems (Super bag and Cocoon™)||Hermetic storage using locally available containers||Regular PE bags|
|Insect control||Yes||Yes (limited if not filled completely)||No|
Convenient in usage, easy sealing
Volume adjusts to load, limited dead air space
Can be re-used many times
Guaratee of manufacturer
Does not need a supply chain
|Provides moisture control at low cost|
Requires supply chain reaching farmers
Can be percieved as being expensive
Often inconvenient usage (small openings)
Sealing can be difficult
Is not hermetic.
No insect control.
Since hermetic properties are build in guidelines for proper usage are sufficient.
Transfer of a principle
Users need to fully understand the prinicple to ensure hermetic properties.
Price depends on margins in supply chain and order volume
in March 2011:
Super bags (50kg): US$ 1-4
Cocoons: US$ 175-60/t capacity. Examples:
Depends on price of local containers
Cheap investment but if insect attack high follow-up cost from losses.