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Sub-Saharan milk cooler project awarded $1m grant

By Mark Astley+

Last updated on 11-Feb-2014 at 09:55 GMT2014-02-11T09:55:04Z

Kisaalita (right) working with an undergraduate student on the milk cooler.
Kisaalita (right) working with an undergraduate student on the milk cooler.

A US engineer has been awarded $1m (€735,000) to complete the development of a biogas-powered milk cooler for sub-Saharan dairy farmers that lack access to refrigeration.

William Kisaalita, a professor of biological and mechanical engineering at the University of Georgia College of Engineering, was awarded $1m by the US Agency for International Development (USAID) in partnership with Duke Energy Corporation, the Overseas Private Investment Corporation, and the Swedish and German governments, to continue his work on the milk cooler.

Thanks to the grant, Kisaalita expects the technology, which is powered using biogas produced through the collection of cow manure, "to be up and running in three years.”

Speaking with, Kisaalita said that once completed the cooler could boost the “quality and quantity of milk entering the cold chain” in sub-Saharan Africa.

Boosts "quality and quantity"

Small-scale dairy farmers in sub-Saharan Africa account for around 80% of the milk produced in the region, according to Kisaalita. The majority, however, do not have access to refrigeration units or the electricity to power them.

This, according to Kisaalita, means farmers in the region lose up to 59% of their milk to spoilage - particularly milk collected in the evening.

“Many times I have seen farmers lose milk, especially in the rainy season because they cannot sell it,” said Kisaalita.

“This development will help African smallholder farmers by preserving their evening milk overnight so it can enter the cold chain the next day.”

“It would give a boost by increasing the quality and quantity of milk entering the cold chain,” he said.

Evaporative cooling 

The refrigeration unit uses the principle of evaporative cooling to reduce the temperature of the milk.

Within the unit, a container of milk is surrounded by water. This cooler is then depressurized with a vacuum pump. A disk containing an absorbent material called zeolite captures the evaporating water, which is turn causes the temperature inside the cooler to decrease.

“It’s the same phenomenon that occurs when you jump into a swimming pool and then you come out on a windy day,” said Kisaalita. “If there’s water on your skin, you will feel cold. The same principle is applied in chilling the milk.”

Once chilled, the milk is kept fresh overnight and can be marketed the next day.

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