At approximately 5% of the dairy farm’s total greenhouse gas (GHG) footprint, energy use is one of the smallest on-farm contributors when compared to manure management and feed production.
Though modest, the ability of dairy farms to generate energy through wind, solar and converting biogas into electricity or renewable natural gas (RNG) tips the scale to balance out any negative effects unable to be mitigated in other areas of the farm.
Energy use
A few years ago, the West Central Research and Outreach Center (WCROC) in Morris, Minnesota, conducted a study to determine the baseline energy use on dairy farms. Electric loads on four farms, ranging in size from 200 to 9,500 cows in west-central Minnesota, were evaluated for six months.
Preliminary results revealed fans were the largest electrical load with usage during the summer ranging from 36% to 59% of the total electricity measured.
Three of the farms had greater electricity usage for milk cooling using compressors and chillers compared to the farm with a direct-load system.
Lighting use ranged from 7% to 21% of the total electricity use measured, and the average monthly energy use for heating ranged from 5% to 32%.
The WCROC researchers, including Brad Heins, dairy scientist; Kirsten Sharpe, University of Minnesota graduate student in animal science; and Michael Reese, renewable energy director, suggest several ways farms can improve the efficiency of a dairy farm’s electrical components to improve the carbon footprint.
For fans, regular maintenance, proper control settings, design, sizing, location, selecting energy-efficient fans and motors, and other factors could influence their efficiency.
There is also potential to reduce energy usage by upgrading to more efficient lighting systems such as LEDs.
Information on a University of Wisconsin Extension energy-efficiency website attributes almost half of a farm’s electrical use to milk harvesting, including the vacuum pump, milk cooling and water heating.
For vacuum pumps, it recommends a variable-speed drive for 30% to 80% in energy savings. Making sure the pump is not oversized and keeping drive belts in good condition and tight will also save in energy.
Scroll compressors, in-line milk cooling and well water precoolers (heat exchangers) are options to save energy in milk cooling.
Energy generation
Dairy farms can generate electricity from the installation of solar panels and wind turbines. Anaerobic digesters capture and produce biogas, which can either be used to generate electricity for use by the dairy or sold to the grid, or it can be sold as RNG after it is cleaned, compressed and injected into the natural gas pipeline.
According to EPA’s AgStar program, there are 273 manure-based anaerobic digestion systems operating in the U.S. today and another 60 currently under construction. In 2020, these digesters generated 1.46 million megawatt-hours equivalent of energy.
About 81% of the country’s digesters are located on dairy farms, primarily in the Midwest, Northeast and California.
AgStar estimates that RNG projects are technically feasible for 2,700 more dairy operations in the U.S. with the potential to reduce GHG emissions by 29.9 million metric tons carbon dioxide equivalent.
As part of its commitment to sustainability, Dairy Farmers of America (DFA) is forming partnerships and strategic alliances to help scale anaerobic digester developments across the country.
“DFA is made up of thousands of dairy farmers across the country who are just as diverse as the entire dairy farm population in the U.S.,” says David Darr, senior vice president, chief strategy and sustainability officer, DFA.
“Our approach in supporting our members on sustainability is really to take an individualized approach based on the region that farm is in, based on the local environment that the farm operates in and based on the demographics of the farm itself,” he says.
A majority of the current digester projects they are working on are on farms with 3,000 cows or more. In addition, DFA is looking at digester opportunities for farms with 200 to 2,500 cows.
Darr says, “We don’t see digesters as a perfect solution for every farm in the country, but we are seeing tremendous growth and opportunities with digesters to be able to further dairy farms on their sustainability journey.”
That wasn’t always the case. Until five or six years ago, most dairy producers interested in installing an anaerobic digester had to finance and manage the operations of the system on their own.
More recently, incentives for low carbon fuels stimulated more utilities and companies to procure renewable energy and RNG.
“We have seen a strong influx of capital – billions of dollars – coming to the dairy industry to want to invest with and partner with dairy farms on anaerobic digester systems that can lower a dairy farm’s greenhouse gas emissions, provide renewable energy for communities in our country and provide diversified revenue streams for dairy farms as well,” Darr says.
He adds, “It’s been a paradigm shift in the model for anaerobic digester development that has really advanced the number of projects taking place across the country.”
These projects are driven by their ability to generate RNG credits that can be sold through the federal Renewable Fuel Standard as RINs and California’s Low Carbon Fuel Standard as LCFS credits.
RINs are generated when dairies inject biogas into existing natural gas pipelines and the natural gas is purchased by the end users in the transportation sector nationwide.
LCFS credits are generated by every ton of carbon emissions offset by biogas production. To qualify, a dairy must receive a carbon intensity (CI) score from the California Air Resources Board, and its RNG needs to be transported through pipelines or other means to California and used for transportation there.
As an example, Mark Stoermann, chief operating officer for Newtrient, says the cost of natural gas is around $3 per million Btu’s. A dairy with a typical CI score can get $95 per million Btu’s from RINs and LCFS credits. “That spread of $92 is enough to make good projects,” Stoermann says.
“The challenge right now is: Unless you’re able to get a project that’s big enough to go to the renewable natural gas route, the economics just aren’t there,” he adds.
Anaerobic digesters producing renewable electricity must compete with wind and solar. “It costs more to build a digester and then put a generator behind the digester and generate electricity that way than it does to put up a wind turbine or solar panel,” Stoermann says.
There have been digesters shut down on dairy farms after their initial power purchase agreement expired because it cost the farm more to operate the digester than the income it was generating.
“Ultimately, what we have to do is create markets, because the technology is there,” Stoermann says. “We have the technology to make renewable energy on almost any size dairy farm. We just don’t have the market for renewable energy that supports that technology.”
The Cow Power program in Vermont is an example of a market supporting anaerobic digesters on smaller farms. Depending on the size of the farm’s generator, they can get 21 cents per kilowatt-hour through the program, where most farms in other states can obtain only 3.5 cents per kilowatt-hour selling to the grid.
“They have digesters on farms as small as 250 cows, but they have a market, and people are happy they have the option to buy renewable energy through the Cow Power program,” Stoermann says.
It has resulted in a considerable number of digesters per capita – more than any other state – even though Vermont is not one of the largest milk-producing states in the U.S.
A potential market opportunity for dairy farm anaerobic digesters is taking in organic substrates like food waste bound for landfills. These substrates can boost the farm’s renewable energy output, as well as offer another income stream, but current policies limit their use.
Producing more electricity with added substrates is still not sustainable if the price offered by the public utility is less than the cost of production.
Both the Renewable Fuel Standard and LCFS value livestock manure greater than organic substrates and will reduce their incentives paid to the farm if substrates are added.
Some farms are able to gain additional income by charging tipping fees for disposing of a company’s food waste. However, there is a lot of room to expand the financial incentives for farms accepting food waste. Policies could be developed to reward dairy producers for reducing landfill volume, emissions and costs.
Beyond digesters, DFA is working with farms on solar production that can come from their operations to either offset some of their own electricity used or, in some cases, produce surplus solar energy that can go out on the grid for use in their communities.
Darr says he is keeping an open mind to what might be coming. “There’s going to be tremendous innovation, and the best thing the industry can do is to stay attuned and open-minded to the innovation coming and see how it could fit within our sustainability strategies and goals,” he says.
Stoermann is driven to see the dairy industry reach net zero and beyond. “We are not stopping in our innovation in our efforts to address the environmental issues on farm,” he says. “We’re not just stopping at zero. We would love to get to an opportunity where we could capture all the enteric emissions and all the manure emissions and convert them all to renewable energy that could replace fossil fuels.”
Every step along the way toward reducing energy use or generating renewable energy will help.
“If all you can do is change to LEDs the next time you change out your lights, that’s a benefit; it lowers your carbon footprint,” Stoermann says.
“There are opportunities out there, and there are going to be more and more opportunities as we continue to understand how dairy can move down this road. Every little bit counts, and every farm will contribute their share,” he says.
