Milk Chilling Live Q&A with Coolsense

Milk Chilling Live Q&A with Coolsense

1 August 2022

In the final installment of our Farm Source Seasonal Focus Live Q&A series on milk quality, we talked to Farm Source Projects Manager Paul Mulligan and Allan Steele of Coolsense, a Hamilton-based company offering refrigeration and thermal energy storage systems. The session focused on the importance of milk chilling to retain product value, as well as recent and upcoming regulation changes in this space.

Recent changes in the milk cooling and refrigerant space

It has become clear, Paul Mulligan says, that a class of gases called HFCs (hydrofluorocarbon), which were designed to replace CFCs (chlorofluorocarbon), have very high global warming potentials (GWPs). Steps are being taken to phase down these gases.

"From a New Zealand farmer perspective, one of the most common gases, R404a, which is in use in 50-60% of on farm refrigeration systems, has a very high GWP and has been subject to phase down since 2020," Paul says. "We're expecting that gas will become increasingly expensive over the next five years and practically unavailable in that time frame. In the past five years, we've seen around 1000% increase in the cost at the farm gate for that gas, for the purposes of recharging farm refrigeration systems."

"It's also become apparent that farmers are largely unaware of the details around this. So we're trying to highlight those issues," Paul says.

Recent changes in the milk cooling and refrigerant space

Preparing your farm to prepare for gas changes "The age of your system is an important parameter," Paul says. "Some of the older systems are still using R22, which is a CFC (chlorofluorocarbon) and practically impossible to source.

The maintenance of the system is another critical component. If you're starting to see regular or emergency maintenance bills, it's probably time to consider changing or upgrading your refrigeration system. It's really important not just to focus on the initial capital cost but also the full lifetime cost of the system."

Paul and Allan are having many discussions with farmers to stress the importance of the gas changes.

"One way of highlighting how important these gases are is to give you an idea of the scale of the gas that's used around the milk chilling vats in NZ," Paul says. "There's roughly 400 tonnes of the stuff. The Ministry for the Environment estimates roughly 15% of that leaks per year. The impact of that leakage on average is the same as every New Zealand dairy farmer driving seven Corollas for a year1. That's why there's a focus on it at the moment."

Gas types to consider

There have been four generations of refrigerant," Allan says. "We all remember the hairsprays having CFCs in them and being dreadful for the ozone layer. We've moved on since then. The second generation was better for the ozone, but had a high GWP. The third generation, which most farms are using now, have a high GWP, as much as 4000 times more than CO2. They are being phased out from 2020, so we're two years into this. By 2025 the last of the gen-three refrigerants will be very expensive, if not unavailable.

"So really you should be looking for the fourth-generation," he says. "That's where the challenge occurs, because the industry has had to move to these fourth-generation gases, at more of a pace than we've been used to. There's very little out there that uses a fourth-generation gas. So you've got two options. You've got the natural, which is CO2, and you've got fourth-generation gas under 500 GWP and they are things like R454b. They're the only two things we've seen in the marketplace at this stage. But everybody is scrambling to offer alternatives."

Key points for upgrading technology

"The most important thing about a refrigeration system on farm is that it chills the milk," Allan says. "Snap chilling is the best way to get the best quality milk into the vat. It also facilitates the heat recovery into the hot water and there are economic benefits that come with that."

Key things to look for when upgrading, Allan says, are machines that comply with the NZCP1 standard. "The best way to do that is to buy a machine that snap-chills the milk on the way into the tank, and to future-proof it, so make sure that you've got a fourth-generation gas and the refrigerant, and longevity. You really want a component built to a standard that will last 15-20 years.

"The fourth-generation refrigerants have energy efficiency ratings of up to four. What that means is one unit of electricity equals four units of cooling and heating, whereas the current technologies on the farm have energy efficiency ratings of about two and a half. With the modern system designs, you can have a very small refrigerant charge on your farm as well. Maybe less than 20% of what farms currently have."

The last key point, Allan says, is ensuring you have the right support. "If you're going to buy a refrigeration system, it's got to be supported. You need to trust the dealership or the on farm refrigeration serviceman implicitly. And you've got to take their advice really, because otherwise you have to be a bit of a refrigeration expert. Doing your due diligence is really important.

"They're all rectangular boxes but they have very different items inside," Allan says. "We've seen some very disappointed farmers that put in a machine that only lasted five years. It's commonplace. Talk to your neighbours, see who's getting the best result. Having a support network means you're going to get looked after."

For more information about seasonal focus milk quality, talk to your local Farm Source TSR or reach out to the team at Coolsense.

The full session is available now at or watch below.

1 Hydrofluorocarbon Consumption in New Zealand, report prepared for the Government of New Zealand, Ministry for the Environment, October 2017.