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Cocoon being closed in Sri Lanka |
Special PVC plastic bags with a barrier
zipper allow for an air tight or hermetic seal. This effectively prevents water
and water vapour penetration which will reduce grain loss due to moisture.
Insect pests, which will always be in the food, will help deplete available
oxygen replacing it with carbon dioxide, and therefore result in the pests
‘suffocating’. Additionally this atmosphere should inhibit the growth of
mould and aflotoxin, which can cause serious health risks. Roughly 10 days are
required for the atmosphere to be sufficiently altered by natural processes to
kill the insects and to stop mould activity—the exact number will depend on
the extent of the infestation with the heaviest infestations dying off the
fastest.
Rodents are also said not to be able to penetrate the PVC and
consume the contents. The GrainPro Cocoon is closely related to the Volcani Cube
which was developed in the late 1980s at the Agricultural Research Organisation
in Israel, by a design team led by Dr Laurence Simon, GrainPro’s Chairman.
Pesticides avoided
Examples of pesticides often used in grain storage,
and therefore avoided with this system are: bioresmethrin, bromophos, carbaryl,
chlorpyrifos, dichlorvos, fenitro-thion, lindane, malathion and pirimiphos
methyl. The GrainPro Cocoon would also provide an alternative to the fumigant
methyl bromide.
PVC concern
A special PVC formulation is used because it is the
only formulation found to combine the high degree of impermeability,
flexibility, long-life, non-toxicity and easy repair. In the long-term,
environmental concerns are being raised about PVC production (see page 3). There
is sensitivity to this, according to Joseph Axelrod, President of GrainPro who
says the company is actively seeking an alternative, but will not be able to
deploy one until field trials ensure that the new material would be reliable.
Rodent attack
The Grain Marketing Board of Zimbabwe expressed
concern about the effectiveness of PVC against rodent attack, which would
consequently affect moisture levels and lead to rotting conditions. If, however,
the plastic is stored properly in the supplied storage bag or is filled and is
under tension, rodents will not chew through it. As a precaution, a field patch
kit is supplied, containing extra PVC and solvent. Repairs can be made on the
spot with no special expertise.
Cost effectiveness
Post-harvest losses have been estimated to be less
than 1% with the GrainPro Cocoon, according to the manufacturers. This compares
with 15-20% losses often experienced with other forms of storage. Sri Lankan
farmers using the GrainPro had a net income increase of 30% by allowing better
control of the time of sale with less fear of storage loss. The cost of
insecticides and fumigants are eliminated and there are very little labour or
operating costs. When used in emergency relief, GrainPro Cocoons greatly reduce
the 40% losses that professional emergency relief managers claim occur in
feeding operations.
The GrainPro Cocoons are available in a variety of sizes (5
metric tonne [MT] to 50 MT capacities). There is also a silo shaped model (50 MT
to 1,000 MT) which handles bulk commodities in addition to bagged ones. This is
important because communal and national level buffer stock storage needs can be
met (where pesticides are also heavily used potentially affecting large
populations) in addition to on-farm and village level needs.
Contact: Joseph Axelrod, President
GrainPro, 304 Newbury Street, Suite 302, Boston, MA 02115-2832, USA, tel: (1)
617 859 4885 fax: (1) 617 347 1740.
[This article first appeared in Pesticides News No. 23, March 1994, page 19]