Milk Quality and Saving Energy Can Work Hand-in-Hand
With input costs on
the rise around the country, dairy producers are looking for ways to reduce
their overhead. One often overlooked, but costly nonetheless, is energy
costs. According to a study of dairy farms in New York state published
in 2003, dairy farms use between 800 and 1,200 kilowatt hours per cow
per year with some operations as high as 1,736 kWh. This study also reported
that 46 percent of all electrical use was for milk harvesting, specifically
milk cooling, vacuum pump, and heating water.
One of the best pieces of
equipment producers can purchase to save on energy usage is a refrigeration
heat recovery unit which captures reject heat from a farm's refrigeration
system and uses it to preheat water. "When properly installed, a heat
recovery unit can reduce a farm's hot water costs by 50 percent," explains
Scott Sanford, a senior outreach specialist with University of Wisconsin-Madison.
This system, which consists of simply a water tank surrounded by a heat
exchanger, can heat water to 100 to 120 degrees F before it enters the
hot water tank.
Hot water is one of the prime demands on farms, and lack
of it can reduce the effectiveness of detergents for cleaning pipelines
and tanks. If pipelines, tanks, or other milking equipment are cleaned
with water that is not hot enough, detergent solutions are less effective
at disinfecting hard to clean places which will lead to an increase in
a dairy's standard plate count.
Another critical part of producing high
quality milk is cooling. Once it leaves the cow's udder at 101 degrees,
milk must be cooled as quickly as possible for storage at 45 degrees or
less as per requirements of the Pasteurized Milk Ordinance. A temperature
of 38 to 40 degrees is desirable to slow bacterial growth. Milk that is
improperly cooled or not cooled quickly enough will damage product quality
and may produce an off-taste.
Milk cooling is also a process that requires
high levels of energy. As milk moves from the cow's udder to storage in
the bulk tank, a great deal of heat needs to be removed. This creates
a high demand on the bulk tank compressors which on some farms will run
for hours after milking is completed. The Pasteurized Milk Ordinance requires
that milk be cooled to 45 degrees or less within two hours of the end
of milking. If a farm is not meeting these requirements during the heat
of the summer, it won't have enough cooling capacity.
One solution to
cool milk more quickly and to reduce energy demands by compressors is
the installation of a precooler. Typically added between the milk receiver
jar and the bulk tank, a precooler uses well water as a coolant to lower
milk temperature close to the ground water temperature. In the Upper Midwest
and Northeast, milk can be cooled to around 55 degrees. Rapid cooling
through the use of a plate cooler will also reduce the growth of contaminating
bacteria. Better yet, this has the potential to reduce milk cooling costs
by 60 percent through reduction of the demand on compressors.
"This equipment
works by transferring the heat from the milk across a stainless steel
plate into the well water which is flowing in opposite directions," Sanford
explains. "A precooler works very well in parts of the country that have
low ground water temperatures but will not be as effective in warmer climates."
Compressor efficiency can also be improved to reduce energy expenditures.
Sanford recommends scroll compression which is 15 to 20 percent more efficient
than a traditional reciprocation compressor. Producers purchasing a new
bulk tank should ask their supplier about scroll compression. Additionally,
for those who have a bulk tank and experience a refrigeration system failure,
scroll compressors can replace existing equipment for an additional investment
of about $300 to $500.
Sanford advises producers to not overlook energy
costs, even though they only represent about 2 percent of milk production
costs. For producers with less than 100 cows, a heat recovery unit is
likely to be a more cost effective investment because it takes less energy
to cool milk than it does to heat water. "Keep in mind that precoolers
and heat recovery units are competing technologies," Sanford reminds.
"Be sure to evaluate your system to ensure that both pieces of equipment
will be cost effective. In many cases, a heat recovery unit alone may
provide the best return on investment."
References:
Barbano, D., Y. Ma, M. Santos. 2006. Influence of Raw Milk Quality on Fluid Milk Shelf Life. J. Dairy Sci. 89 (E. Suppl.): E15-E19
Sanford, S. 2008. Wisconsin Energy Efficiency and Renewable Energy Resource. 5 Nov. 2008
Ludington, D. and E. Johnson. 2003. Dairy Farm Energy Audit Summary Report. New York State Research and Development Authority. Available at
United States Food and Drug Administration. Grade "A" Pasteurized Milk Ordinance, 2007 Revision. Available at:
This article first appeared in the NMC Media Newsletter
"Udder Quarter", December 2008.
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