Getting milk from cow to customer is a fairly straightforward proposition: milk the cows, collect the milk from a bunch of different animals, transport it to a processor to get it ready to consume, package it and distribute it for sale to consumers.
At least, that’s how it goes in the developed world. But even with dairy cows dotting the landscape of countries like Uganda and India, the fresh milk supply often breaks at its earliest stages, leaving a void that can deprive children and adults of valuable nutrition, energy and food security.
The problem is refrigeration—not for consumers but for the farmers who milk their cows in the morning and evening. Morning milk can be punctually dispatched to a chiller, which slows bacterial growth in the fluid by dropping its temperature. But without proper cooling, the evening’s milk turns bad by the time it could be transported to a bulk collector and then on to a processor. Along with the waste, poor farmers miss out on valuable lost income.
It’s a big issue for a place like Uganda, where up to 80 percent of the dairy sector is made of small farmers who must chuck as much as half of their daily milk production because of spoilage.
“I’ve known this problem for many, many years,” says William Kisaalita, a University of Georgia engineering professor originally from Uganda.
He says the issue goes beyond just installing refrigerators at farms and dairies. In fact, it’s more an infrastructure problem—most farmers don’t have access to electricity, and other power sources like kerosene and solar are too expensive or difficult to operate.
Similar roadblocks to a stable milk supply are rife around the world. The average human consumes almost 28 gallons of milk a year, according to the U.S. Agency for International Development (USAID). But in Africa, consumption stands at less than 11 gallons a year. Indians, meanwhile, consume around 18 gallons of milk a year on average, according to 2009 Food and Agriculture Organization data.
The importance of keeping milk cold to prevent spoilage is such an important development issue that USAID recently offered funding to several alternative energy refrigeration technologies that show promise. Under the agency’s Powering Agriculture: An Energy Grand Challenge for Development, 12 winners will split $13 million to advance clean tech for the agricultural sector in the developing world. The program is being run in partnership with the Swedish and German governments, Duke Energy and the Overseas Private Investment Corporation.
Evaporation and manure cools milk
Kisaalita and the University of Georgia Research Foundation earned one of the awards for a two-part refrigeration system. For the cooling component, a large container of milk is placed inside a second unit holding water. A vacuum creates suction above the water, which vaporizes it. Like droplets on a person who has just come out of the pool, this water vapor pulls heat out from the milk using a phenomenon called evaporative cooling. The vapor is then absorbed in porous plates made out of minerals called zeolites. Kisaalita says milk can be cooled to its target temperature within two hours.
The second component is called the regeneration unit, which is basically an oven that dries the wet zeolite so it can be reused. A substance that dairy farmers have plenty of access to—biogas from cow manure—powers the oven, which can reach a temperature of around 400 degrees Fahrenheit. “The farmer can produce enough biogas to power the oven and for cooking and lighting,” he says. “That’s a very good side benefit.”
The system, which will likely cost around $350, can currently hold more than 26 gallons of milk at 46 degrees Fahrenheit for up to 70 hours. That temperature is enough to meet African standards, though he hopes to get it working well enough that it meets international norms of 39 degrees F so dairy can be exported.
He says it will go a long way to saving the half of milk that rural producers must throw out. “If these farmers can keep their evening milk until the next morning so it can enter the supply chain, they automatically double their income,” Kisaalita says. “Plus, this empowers the farmer to wait for the best deal they can negotiate from bulk buyers because they can hold their milk.”
He says he’ll use the USAID grant to construct 50 units and give them to farmers to monitor and improve how they work.
USAID also awarded Boston- and India-based Promethean Power Systems a grant for the company’s thermal energy battery pack, which charges on a few hours of electricity. The system is designed for rural conditions in India, where grid electricity may be available but highly intermittent.
“In India, they have such unreliable power that it’s virtually impossible to get milk to the market without dangerous levels of bacteria,” said Sam White, Promethean cofounder and director, during a July 2013 TedX talk. “And every Indian knows as soon as they get that pouch of milk, the first thing they do is boil it. And, yeah, it does take away a lot of that nutritional value that Indians depend on.”
Many rural farmers and dairies have been forced to rely upon diesel generators to make up the energy deficit to cool their milk, but this is expensive and spews exhaust into the environment. Farmers must motorbike their milk to distant collection points, which pushes the average time it takes to chill it enough to slow bacterial growth to six hours. That’s a full two hours later than the internationally accepted limit for chilling.
To answer this problem, Promethean over the course of six years developed a 264-gallon milk chiller with a 132-gallon thermal battery. The device uses occasional grid electricity to cool a mix of fluids and phase-changing materials to below freezing. The unit doesn’t store electrical energy; it holds thermal energy by efficiently making ice. This process rapidly chills milk from 95 degrees F to 39 degrees F. As of July 2013, 50 villages had installed the system and were chilling their milk immediately after it came out of the cow.
But the problem goes beyond just dairy spoilage. Keeping agricultural products from spoiling before they get to consumers is a major focus of the USAID grants and of those who won them. Exacerbating the issue is the fact that more of the world’s population is moving into the middle class, where they are demanding an increasing supply of higher quality food. Eight of this year’s awardees have technologies that could potentially improve cold storage and power availability for agricultural processing.
“Here’s a statistic to give you an idea of how large this problem is,” said White. “In the United States, 80 percent of food that’s grown on farms gets processed. In India, just six percent makes it to the cities in a quality-enough state to get processed. Every year alone, $13 billion of food gets spoiled, and a good percentage of that spoilage is milk.”