Aiming for dairy farm energy efficiency
by Courtney Llewellyn
It’s no secret that dairy farms use a lot of energy. Luckily, as technology advances, so do the opportunities for energy efficiency. A group of experts discussed the topic during a Farm Energy Day virtual presentation from Penn State Extension.
Dan Ciolkosz of the Penn State Extension Department of Ag & Bio Engineering kicked off the webinar by explaining what a representative dairy in Pennsylvania looks like: It has 100 cows being milked and 30 cows not being milked out in freestall barns. Milking takes place two or three times daily in an adjacent parlor. There are about 200 acres of corn, soy and hay being grown with no irrigation. There are 482,000 cows in PA, but only 10% are dairies. These farms produce 4.6 billion liters of milk annually and represent over $2 billion of farm income.
So where is the energy being used on an average dairy? 50% goes to milk cooling and ventilation; 18% is for milk harvesting; 17% is for lighting; and the remaining 15% is for electric water heating and other uses.
But there are different kinds of energy. Ciolkosz explained that environmental energy is sunlight and wind, and it actually dwarfs all other energy on the farm. Primary energy (electricity, diesel fuel, heating oil, propane, cordwood, generated heat or electricity, including that from solar and anaerobic digesters) is anything used to create power and heat. Embodied energy is found in equipment, fertilizer and chemicals. “When you tally it all up, its equal to or even more than primary energy,” Ciolkosz said of embodied energy. (There’s additional energy in manual labor, feed purchased and even milk – which is energy leaving the farm.)
“Energy efficiency is about minimizing primary energy use without harming farm productivity,” he stated.
His research has found that a dairy farm will typically have a base load (the amount of energy used daily) and a temperature-dependent load – the hotter it gets, the more energy that’s required for refrigeration.
Primary energy is used in the milking center (for the vacuum pump, transfer pump and refrigeration), the barn (for ventilation, lighting, feed handling and manure handling) and in the fields (for field prep, planting, harvest and irrigation).
To know how efficient your farm is, Ciolkosz said to add up all your farm energy use over the course of a year and divide your kilowatt-hours by the number of cows being milked. “If your answer is 1,500 or higher, there are significant opportunities to reduce energy use and costs in a very effective manner for your farm,” he said.
Ed Johnstonbaugh of Penn State Extension Westmoreland County then spoke about milking system energy efficiency options. “Take stock of where your operation stands today. It’s important to know where you stand,” he said. “And if it’s not broke, don’t fix it. Just make sure your equipment is running well.”
He noted specifically that vacuum pumps with variable speed drives adjust their operation to accomplish their task with high efficiency. Electric motors are the most efficient when they’re sized for the task at hand. Since harvesting milk is a variable task, having the right sized equipment is key.
State of the art equipment can raise your energy efficiency (especially solar/photovoltaic, as that means you avoid purchasing from the electric grid). Air-to-water heat pumps run at 300% efficiency, which means for every penny you spend, you get three cents of energy, Johnstonbaugh explained. With biomass, you can grow your own energy. Also, ground source heat pumps recover heat from the earth.
“Assuming the ground source heat pump toggles between water heating and milk chilling … installing a ground source heat pump with a coefficient of performance of 400 would save $40 for every $100 now being spent for heating water and chilling milk,” he said.
Energy and Environmental Lead with PennTAP, Denise Bechdel focused on specific areas of efficiency. When looking at ventilation, she suggested looking at efficiency ratings in “natural” ventilation, interior air circulation, forced air ventilation and tunnel ventilation systems. She said to choose efficient fans, larger fans and those that use a direct drive.
Bechdel also offered tips on how to keep systems effective: use the set points and controls in electronic systems, clean the fan blades and shutters and incorporate sprinkling or evaporative cooling for the hottest days.
When it comes to silage, Bechdel said bunker silos are generally more efficient than upright silos, but there can be an impact on feed quality.
As for manure handling system energy productivity, she noted motors may be upgradable to higher efficiency models and control systems can impact energy usage by controlling frequency of use. However, when considering manure systems farmers must also think about the impact on cow cleanliness and health.
Bechdel suggested dairy farmers have an expert visit their barns for an energy audit. The USDA Rural Energy for America Program (REAP) is a resource for funding that farmers can look into, and every state has energy coordinators.
Visit extension.psu.edu/new-online-tool-can-help-you-take-control-of-your-energy-habits for another resource on energy efficiency.