Bulk Milk Coolers: A Cool Way to Chill for Dairies and Farmers

Published Feb. 23, 2017

By Garima Rakesh Mishra for The Indian Express

In 2013,
Promethean Power Systems
(United States) received a Powering Agriculture award for the
Market Growth (Stage 5) of
Energy Efficiency
Solar Photovoltaic
solutions for
Cold Storage
in the production of
Dairy
in
India

About Powering Agriculture

Powering Agriculture: An Energy Grand Challenge for Development supports the development and deployment of clean energy innovations that increase agriculture productivity and stimulate low carbon economic growth in the agriculture sector of developing countries to help end extreme poverty and extreme hunger.

Milk is best when fresh chilled at source — and it can be done even with erratic rural power supply.

The near-quadrupling of milk procurement by dairy cooperatives in Gujarat over the last 15 years — from an average of 45 lakh litres to about 170 lakh litres per day — has been attributed no less to a single factor: 24-hour power in rural areas, including guaranteed three-phase supply for eight hours, enabling village-level societies to install bulk milk coolers (BMC). These, with capacities ranging from 1,000 to 10,000 litres, chill the milk to around 4 degrees celsius at the primary collection point itself, inhibiting microbial growth that can lead to undesirable quality/taste changes and expedite spoilage.

But maintaining the freshness of raw milk sourced from farmers isn’t all that the BMCs have done.

In the pre-BMC era, the milk collected by the society had to reach the dairy plant by 8:30 am or so, before day temperatures rose. It required procurement to start by 6 am and farmers undertaking milking at least an hour earlier, so as to not miss the tanker. The sheer need to hurry through the process, moreover, limited the number of animals that could be milked. With BMCs, the milk was chilled at source and remained fresh, which gave farmers the flexibility to deliver even at 9 am. They could now afford to expand their herd size and supply more milk. Today, an estimated 80 per cent of milk collected by Gujarat’s dairy unions comes through BMCs and it is not difficult to see the link between these and higher procurement volumes.

Not every state, unfortunately though, is Gujarat — where farmers have assured electricity supply allowing milk to be chilled not very long after it has left the udders of cows or buffaloes. In much of rural India, power supply is irregular, which means even BMCs cannot do without the backup of diesel generators.

This is where an innovation by Promethean Power Systems, a Pune-based company founded by two men from Boston has made a difference. In 2011, Sorin Grama and Sam White built the final prototype of a Rapid Milk Chiller (RMC) based on a proprietary Thermal Storage System (TSS) technology. At the heart of it lay a thermal battery, which drew and stored electricity from the grid as and when available. This stored energy it then released to rapidly chill the milk collected from farmers at ambient temperatures — say, 35 degrees — to 4 degrees Celsius.

The duo initially sought to establish the feasibility of a solar-powered milk chilling solution. While the trials were successful, their prospective customers, however, wanted a system that was less bulky (solar panels take up too much space), more cost-effective (which was not the case with solar technology in 2010), and easier to operate. Further, solar-based chilling wasn’t seen to be necessary in places where there was at least intermittent power supply, even if unreliable. The thermal battery could be charged whenever electricity was available; the trick was to decouple supply of power from chilling. From this emerged the alternative TSS technology, which was more economical and better-suited to general Indian rural conditions.

Grama and White launched the TSS-based RMC as a pilot project six years ago near Goa. In 2013, Promethean Systems began commercial operations in India. “We have so far sold over 500 units in the country and these have already chilled more than 150 million litres of milk supplied by 25,000-plus farmers,” says Jiten Ghelani, CEO of the company.

The system’s main advantage is the flexibility it gives for chilling milk at village level, even without consistent grid power or diesel generator backup. “Typically, BMCs run on gen-sets for 50 per cent of the time, resulting in both high operational costs and 25-30 per cent more carbon emissions,” notes Jofi Joseph, Director of Sales & Marketing.

Chilling at source is a win-win for both dairy plants and farmers. Milk is a good medium for growth of microorganisms. Chilling within about an hour of milking basically prevents the build-up of bacteria converting the lactose or sugar in the milk into lactic acid, which curdles the proteins and causes souring. Dairies, then, get access to milk with less microbial load and spoilage possibility, while farmers, too, benefit from flexibility with regard to delivery time and increased herd size. Besides, they can expect to fetch a quality premium in terms of price per litre.

“The buyers of our RMCs aren’t individual farmers. The processors sourcing milk from them are the ones investing in the equipment, costing Rs 5-6 lakh each, and installing these in their respective village-level collection centres”, explains Ghelani, whose company claims to have developed a customer base across Tamil Nadu, Maharashtra, Andhra Pradesh, Telangana, Rajasthan, and Uttar Pradesh.

Amul dairy currently has a collection centre at Pahad Dhara, a village in Pune’s outskirts, where it has put up an RMC. “Earlier, we had a regular BMC that used to operate most of the time on diesel, entailing a monthly expense of Rs 35,000 a month. With the RMC, which was installed roughly a year ago, we are now spending only Rs 5,000 on electricity”, notes Devadnya Dilip Wagh, a coordinator at the chilling centre that procures an average 600 litres per day of milk from 20 farmers in the village.

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Promethean's system allows for chilling milk at source, which is a win-win for dairy plants and farmers. Dairies get milk with less microbial load and spoilage possibility; farmers benefit from a more flexible delivery time and increased herd size. They can also expect to fetch a better price.

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Word is spreading about the transformative impact of Promethean's milk chiller technology. The company has sold over 500 milk chilling units to its dairy partners in India, Sri Lanka and Bangladesh. Retailers are also using Promethean’s system for refrigerating produce.

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Sorin Grama and Sam White of Promethean Power are finding their stride in India, where their thermal energy storage technology is making a real difference in the lives of Indian dairy farmers—without using a single drop of diesel.