Agri Article: Absorbent Beads- Seed Drying
Raja Vadlamani: Head of Supply Chain-Asia at Seedworks International Pvt. Ltd.
Seed storage a major problem because the majority of the world’s poor countries are located in the tropics, where the combination of high temperature and high relative humidity causes rapid deterioration of seed quality. In South Asia, seeds harvested before or during the monsoon season need to be dried and stored until the next planting season. The relative humidity of the air for most of the period between harvest and planting often exceeds 75% and temperatures remain above 30°C, causing seeds to deteriorate rapidly. Seeds absorb water from the ambient air when they are stored in humid environments and lose water when stored in low relative humidity. Generally speaking, a seed’s longevity is reduced by approximately half for every 1% increase in seed moisture content (water content as a percent of fresh weight) or 5°C increase in temperature, and the effects are additive. Thus, seeds stored at 10% moisture content and 30°C will last only one-quarter as long as seeds stored at 9% moisture content and 25°C. This principle implies that seed storage life can be enhanced considerably by lowering both moisture and temperature. However, moisture content is the key factor that can be lowered for successful seed storage in tropical countries. Cold storage is expensive and difficult to maintain because electricity supplies are often inconsistent and unreliable. In addition, seeds that are dried to low moisture contents are more tolerant of storage at warm temperatures. However, even prolonged sun drying in high humidities cannot reduce seed moisture content to the levels low enough to assure long-term viability.
These problems can be overcome by drying seeds to low moisture contents using inexpensive hermetic containers and drying beads, a recently developed desiccant technology. Using drying beads, seeds can be quickly and efficiently dried to safe storage moisture contents, and storing seeds in hermetic containers not only maintains low moisture contents, it also prevents losses to rodents, insects and molds. Seed desiccant drying beads provide a simple, inexpensive and reusable method for seed drying in humid climates. In addition, the beads can also be used to dry herbs, vegetables, fruit, nuts, medicinal plants, or other horticultural products.The beads are made from zeolites, a class of porous minerals that readily bind with certain materials. In this case, the pores were engineered to be just the right size and shape to trap water molecules. Bradford, a professor of plant sciences at the University of California, Davis, estimates they could cut the energy used in large-scale drying operations in half and, in humid parts of the world, greatly reduce the loss of crops to rot and fungal toxins.
The beads were developed by Rhino Research in Thailand. Bradford and his collaborators there have spent several years testing and refining the technology with local farmers in that country as well as in India, Nepal, Kenya, and other tropical nations, where as much as a third of crops are lost before reaching consumers. In those areas, the beads are placed alongside, say, harvested rice or maize seeds, separated in mesh sacks or screened-in compartments within containers. They then capture water from the air, significantly reducing the moisture that leads to rot and fungal infections.
Now the researchers are working to bring the technology to richer nations at the industrial scale, exploring its use to dry harvested almonds, walnuts, rice, and grains. Typically, farming operations blow hot air through harvested crops as they pass through drying towers or silos. But experiments show that ambient air can work just as well, if it’s first dried by passing it through the beads. The researchers also believe this approach can improve the quality of the end product, because uneven air heating frequently scorches parts of the batch, ruining the taste of nuts and other foods.
The beads themselves still need to be heated in the end, in order to remove the water so they can be reused. But that can be done in a compact space like an oven, which is far more efficient than blowing around heated air.
Source : Absorbent Beads Could Save Energy—and Lives
Zeolite beads are a better, more efficient way to prevent crops from rotting in humid parts of the globe.
by James Temple February 13, 2017, MIT Technology review.