Producing power from cow poop: A Florida dairy aims to reduce climate impact of cattle
At barn No. 5 at the Larson Dairy farm just north of Lake Okeechobee, a line of cows pump out milk bound for grocery stores shelves and family refrigerators across Florida.
Being cows, they are also producing a steady supply of something else — manure, a lot of it.
Poop is an inevitable byproduct of the cattle industry and, like cow burps and farts, it emits methane, a potent greenhouse gas that scientists point to as a major driver of climate change. But an innovative process now in operation at Larson helps reduce the climate impact of this dairy herd, capturing and cleaning methane locked in those cowpies and sending it to a natural gas pipeline near the farm.
Environmentalists and climate change experts, who have long criticized the cattle industry over pollution problems, have plenty of questions and concerns about the process.
But the end result is something that Jacob Larson, a third-generation Florida farmer, sees as a big step forward he could not imagine possible a few years ago: His dairy waste supplements the state’s energy supply and can perhaps even become a valuable product of its own.
“Just the thought process of turning manure into fuel is mind-boggling,” said Larson, during a tour of the dairy’s poop-to-power system, which emerged through a partnership with Brightmark, a waste-to-energy company based in California that has picked up much of the tab for installing and operating the equipment.
Turning poop into power
Since the source of this power is cow poop, the process itself is not particularly pretty. In the dairy barn, a spray system regularly wets down the manure with water to liquefy it, creating a brown stream that flows down a ditch into a concrete reservoir. From there, pipes take it into the heart of the system, something called an “anaerobic digester” lagoon.
The system appears relatively low-tech. From above, a digester consists of large black tarps spread over what looks like a mound. But underneath, it functions like an insulated, oxygen-free underground bunker. Manure goes through four chemical reactions as bacteria feed on it. Depending on the temperature and amount of nutrients in the manure, Brightmark says it can take days to weeks for “bio-gas” to form, cleaned and processed. The company delivered its first bio-gas to a nearby pipeline in August.
Anaerobic digesters are in place on four of Larson’s sprawling farms, fed by a steady supply of manure from some 12,000 cows. The poop-to-power calculation is complicated but by one expert estimate, 10 of the cows at barn No. 5 can produce enough bio-gas in a month to run a typical home over the same period.
“The Larsons take care of cows and produce high-quality cows and high-quality manure,” Larson said. “We commit our manure supply to Brightmark, and they take the manure supply from there.”
After processing, what’s left of the manure is run through a rotating composter that squeezes out water and remaining solids. The dried leftovers, stored in piles, and the remaining liquid are used as fertilizer on the farm.
“It’s like recycling, that’s the beauty,” said Rishi Prasad, an environmental science professor at Auburn University who is not affiliated with Brightmark but has studied the process involved. “You are basically recycling manure on the farm for energy, for feeding the plants like corn, and then that corn would go back to feeding the dairy cows.”
The methane challenge
Livestock operations, according to a United Nations assessment, account for about a third of all global methane emissions — with cows far and away the No. 1 source. Methane is a particularly problematic greenhouse gas — its warming effect some 28 times greater than carbon dioxide on a 100-year timescale, and more than 80 times more powerful over 20 years, according to the U.S. Environmental Protection Agency.
So reducing methane emissions could make a big difference and is one of the major challenges of curbing climate change. While some activists call for banning or shrinking the cattle industry, that goal hasn’t won much political or public support.
“The whole planet is not going to stop eating beef, or stop drinking milk or stop eating pizzas,” said Prasad, who studied anaerobic digesters as part of his pHd research at the University of Florida. “But we need to think about how we can make the food production industry more sustainable and reduce emissions so we can buy more time.”
California, where Brightmark is based, already has embraced the use of digesters and fueled expansion through a state policy called the Low Carbon Fuel Standard (LCFS) intended to reduce the impact of transportation fuels. Under the complex rules, California views digesters as “carbon-negative” so bio-fuel can be used as a “credit” to balance out fossil fuels in a commercial trading market.
It works this way. While there are no caps on emissions from dairy farms, oil and gas companies have strict limits on emissions produced by transportation fuel. To stay within emissions limits, those companies can either sell fuel with a lower carbon footprint or offset its use.
So at dairy farms, owners of the digesters can sell “carbon-negative” fuel to oil and gas companies like Chevron, which partnered with Brightmark — a transaction that helps offset its own emissions in the California system. Because digesters receive credit both for reducing methane emissions from manure and replacing a fossil fuel, dairy bio-gas is a particularly attractive commodity in the California market, 10 times more valuable than landfill gas.
Brightmark sees a promising future in Florida, where digesters also have been catching on. According to EPA’s database, as of May 2022, there were about 330 anaerobic digesters at livestock farms in the U.S. and over 30 in Florida. Larson Family Farms isn’t included on the list yet. The EPA also sees room for growth in Florida, with one report projecting up to 80 dairy farms as candidates.
“The mission for us is to re-imagine waste and really look at better ways to create environmental benefits associated with the things that we waste,” Bob Powell, CEO of Brightmark, said in an interview with the Miami Herald. “I definitely think the project with the Larsons is a flagship project and one that people can point to.”
Brightmark, Larson and other supporters see the systems as a win-win. Bio-gas creates a new use, and potential revenue stream, from a former waste product.
“We’re going to be offsetting on an annual basis 57,000 tons of CO2 equivalent out of the environment,” Powell said. “And to put that in perspective, that would be the equivalent of planting over 75,000 acres of forest each year.”
Not a cure for climate impacts
But the systems also are not silver bullets and even some supporters say that labeling them “carbon negative” oversells the benefits.
“I don’t think this falls under a carbon-negative scenario,” said Prasad, the Auburn associate professor. “But it is reducing the methane that goes back into the atmosphere by recycling it and not throwing it directly into the environment.”
Ruthie Lazenby, who focuses on energy law and policy at UCLA, said the anaerobic digesters also only deal with one part of the cow emissions problem. They don’t process burps and passed gas, she wrote in a report supported by the United States Department of Agriculture.
“It is imperative that policymakers and others recognize that manure bio-gas systems reduce emissions from only one part of this system—manure management,” Lazenby said in the report.
Manure also happens to be the smallest part of the problem. While agriculture operations overall account for 10% of global greenhouse emissions, only 12% of that comes from manure, according to the EPA. In one study, scientists recorded up to 95% of cow’s methane emissions came from burps and farts.
While the digesters can cut overall methane emissions from a dairy, she and others also worry whether selling bio-gas might actually encourage the expansion of a cattle industry that could potentially offset the benefits of manure-to-power systems. Lazenby believes the industry’s operations need to be more closely regulated.
“Embracing digesters is a profoundly pessimistic approach to greenhouse gas reduction and assumes that the best we can do is pay factory farms to capture a portion of their greenhouse gas emissions,” she said. “Not only that, it invests in a technology that requires the ongoing production of those very greenhouse gasses.”
A study from The Union of Concerned Scientists also showed that California’s system gave a competitive financial advantage to large-scale dairy operations. The EPA, which has embraced digesters, also favors larger operations. In the screening document titled, “Is Anaerobic Digestion Right for Your Farm?” the second question asks how large the farm is and said potential candidates for digesters should have at least 500 cattle.
One estimation calculated that each cow could bring in an extra $1,000 in revenue from carbon credits every year.
“On its face, using bio-gas to power homes and cars might be an attractive approach if you assume that these vehicles are going to be running anyway and this offers an opportunity to displace fossil fuels,” said study author Kevin Fingerman, an associate professor of energy and climate at Calpoly Humboldt State University. “The complication emerges when we ask if there would be as much methane vented if we didn’t have policy promotions for bio-gas.”
“By creating a new revenue stream, does that reinforce large-scale operations?” he said.
Climate impact also isn’t the only concern — particularly in Florida, where environmental groups have long argued that cow manure is also a contributor to water pollution problems and algae blooms — and a major source of damaging nutrients flowing south into Lake Okeechobee. Brightmark believes the digesters will help reduce impacts there as well. In the past, manure would be disposed of in an open-air lagoon with greenhouse gasses vented into the atmosphere.
“Because of the process creating a more stable fertilizer, it reduces phosphorus and nitrogen in the environment and it’s allowed a dramatic water positive impact in our farming communities,” Powell said.
But Prasad and others are skeptical about how much of a difference a digester makes in reducing pollution impacts from fertilizer.
“There is no such thing as a ‘stable fertilizer’ because it has nutrients,” Prasad said. “If you apply the digester’s fertilizer throughout the season everything adds up and putting it in the same places for years can become a problem.”
The EPA also considers the leftover material potentially problematic.
“Digestate [the leftover solids and liquid] is a nutrient-rich by-product from organic waste anaerobic digestion but can contribute to nutrient pollution without comprehensive management strategies. Some nutrient pollution impacts include harmful algal blooms, hypoxia, and eutrophication.”
For one farmer, a family legacy
Brightmark acknowledges that it has aspirations beyond the Larson farms. The company is also interested in developing larger operations, but says not every dairy farm it might contract with will wind up adding cows.
“Brightmark is evaluating farms based on certain sizes,” said Ryan Berger, a partnership coordinator with Brightmark. “Sometimes it does work out to add more cows to that. We have a number of farms that we’ve worked with that have added cows. We have another set of farms that we work with that really haven’t grown.”
For Larson, his family’s goal is to continue a legacy in providing a staple product for Florida — but with reduced impact on the community and state he loves.
“The hours are long, the work is hard and sometimes it’s dirty, but at the end of the day it’s pretty rewarding,” Larson said with a grin. “We feel a lot of responsibility. We’ve been blessed, and when much is given, much is required. We do know that we have a lot to give back. One thing he does question is the contention from EPA and Brightmark that digesters can help reduce odors emanating from a dairy operation. Larson, who has been smelling cows his whole life, isn’t too sure about that. “I can’t say it smells much better.”
Ashley Miznazi is a climate change reporter for the Miami Herald funded by the Lynn and Louis Wolfson II Family Foundation in partnership with Journalism Funding Partners.