Biochar for the future
Diving deep into the process – and the promise | 8
Savvy spreading, simple science
The state of liquid manure sensors | 12
Managing methane
Can additives reduce emissions from stored liquid manure on the farm? | 16
July/August 2025
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JULY/AUGUST 2025 Vol.23, Issue 4
your
Our annual liquid manure issue dives deep into nutrient management, storage, additives and more – plus our regular columns and industry news.
Biochar for the future Why pyrolysis is growing – and standing out – in manure management.
BY TREENA HEIN
Savvy spreading, simple science When it comes to knowing which nutrients are hitting the soil, how close can we get?
BY RONDA PAYNE
Managing methane Canadian study examines feasbility of methane-reducing additives in stored liquid manure.
BY JACK KAZMIERSKI
In just over a month, I will be crossing the Windsor-Detroit border into the U.S. for the 2025 North American Manure Expo in Wauseon, OH. It’s only my second time in Ohio, but I could not be more excited to return to the state – or to the Expo. Yes, it’s my first Ohio Expo, and every Expo has a slightly different flavor, but Expos are kind of like ice cream – there’s a lot of different flavors, but they’re all still ice cream.
If I could compare last year’s Expo in New York, I’d compare it to something a little thrilling and elaborate – like an unexpectedly delicious combo of chocolate and pretzel, or mango and chilli. It had the unique, buzzy excitement of a first-time Expo host, with an unmatched eagerness to step up and seize the opportunity to prove the value of manure – not just to attendees, but to locals curious about this unique farm show.
The past year in Wisconsin was a good butterscotch or cookie dough –zippy, efficient crowd-pleaser whose working components were made possible by the most seasoned of hosts.
I’d compare Pennsylvania 2022 to a fruity sorbet – something that screams, “Summer’s back!” There was the palpable excitement of the first in-person Expo in three years, and an earnest desire to remind people of just how magical the Expo is.
What does Ohio bring? We’ll see. We could easily say that being a previous Expo host, it’s a classic,
like vanilla... but we’re in for many new and exciting Expo components that previous Ohio attendees haven’t experienced, like our safety school and spill demos. Doesn’t sound very “vanilla” to me.
I’ve lived in many different towns and cities in my life, each with different quirks, customs and subcultures. In one of my favorite books, the narrator – a world traveller – remarks that although all countries have different expectations about whether one should remove their shoes when entering someone’s home (spoiler alert: I’m Canadian, so please remove your shoes in my house!) they are united in that they all have customs about shoes at the door.
And so, even though every different host city has a different flavor to the Expo, they are all united in that they have a flavor – and it’s always thoughtful. Each new setting comes with its own opportunities , whether it’s making that crucial first impression, or balancing what we know works with upping the ante.
It’s almost like manure itself –there’s so many different ways to manage and apply it, but it’s still the one thing that unites all the readers of this magazine.
This issue has a focus on liquid manure, which you’ll find in our feature on liquid manure sensors (Page 12) and in our unique deep dive on additives (Page 16) – as well as other handy articles on pyrolysis, heat from manure and more!
Happy reading! •
Last month, MSU’s George Smith (director of the university’s AgBioResearch division) and Wei Liao, director of MSU’s Anaerobic Digestion Research and Education Center, testified before the Michigan House Agriculture Committee, vouching for the critical role that anaerobic digesters can play in the protection of the Great Lakes ecosystem. They cited experiences from MSU’s own full-scale digestion facility, which processes approximately 15,000 gallons of animal and food wastes, including dairy and swine manure, and other food and processing wastes and generates 6,500
kilowatt-hours of renewable electricity and 15,000 gallons of digestate per day.
That digestate has been land-applied across the university’s farmland under Michigan’s Generally Accepted Agricultural and Management Practices, guided by soil test data and monitored regularly. According to MSU, this monitoring has shown no evidence of groundwater contamination.
“Anaerobic digestion is a tool for simultaneously cutting greenhouse gas emissions, recovering nutrients and water, and revitalizing rural economies,” said Liao.
U.S. producers have been cautioned to prepare for the potential threat of New World screwworm, a parasitic fly whose larvae feed on the tissue of livestock. New World screwworm is historically found in South America and the Caribbean, but has been detected this past spring as far north as Veracruz Mexico. The discovery has prompted the U.S. to suspend imports of live cattle, horses and
bison from Mexico as of May 11. At press time (June 11), the ban has not yet been lifted.
USDA secretary Brooke Rollins acknowledged good faith collaboration and efforts, but added that nevertheless “there has been unacceptable northward advancement of NWS and additional action must be taken to slow the northern progression of this deadly parasitic fly.”
Manure Manager parent publisher Annex Business Media and its agricultural group have named the 2025 Influential Women in Canadian Agriculture (IWCA) honorees. The seven women selected for their leadership, innovation and advocacy in the field of agriculture are: Cathy Lennon, Ontario Federation of Agriculture; Athyna Cambouris, Agriculture and Agri-Food Canada; Jolene MacEachern, Dalhousie University; Emily Ford, Quattro Farms; Meghan Scot, Hensall Co-Op; Martine Moulianne, Université de Montréal; and Candace Mitschke, SaskFSA.
The honorees were nominated by family, friends and colleagues. Judges placed an importance on the diversity of agricultural roles to ensure representation from the field to the lab; they also aimed for a balance of career-focused achievements
Rollins added, “Once we see increased surveillance and eradication efforts, and the positive results of those actions, we remain committed to opening the border for livestock trade.”
She emphasized that the suspension is “not about politics” or punishing Mexico, but about livestock and human safety. New World screwworm feasts on the tissue of
live animals, which can cause extensive damage and result in potential herd-culling.
In Canada, the CFIA says it is “monitoring” the situation.
Other experts have added that although these infestations are commonly associated with cattle, swine can also be susceptible to infections.
Experts are cautioning producers to remain vigilant.
as well as community and industry contribution. For example, Boulianne, a professor of veterinary medicine, was hailed both for her field trials on antibiotic-free production systems, as well as her mentoring of early-career scientists. Cambouris has also been equally hailed for her contributions to both research and policy in the field of precision agriculture. Many hold multiple roles; Dalhousie’s MacEachern represents the experience of both farmers and educators, with her nominator acknowledging MacEachern’s unique experience in farm transition.
All seven women will be featured in podcast episodes posted on Annex brands, including Manure Manager, throughout the summer, culminating in the IWCA Summit, a free, live, virtual event on Oct. 21.
The Michigan House Agricultural Committee recently passed House Bills 4257 and 4265, which focus on streamlining the regulatory framework associated with adopting and operating anaerobic digesters in the state.
The bills included training and record-keeping standards and other regulatory provisions.
According to the EPA’s livestock digester database, adoption continues to climb nationwide, with 400 operating digesters in the U.S. in June
Farm Credit Canada (FCC) has made a commitment to invest $2 billion to advance Canadian agtech innovation by 2030 through the organization’s new investment arm, FCC Capital. “Canada’s economic future requires an agriculture and food industry leading the world in innovation and productivity.
However, until now, investment dollars have been scarce and have not scaled to meet the increasingly sophisticated needs of the sector. Through this investment, FCC is delivering on its commitment to be a catalyst and support innovation and productivity in one of Canada’s most important and investable sectors,” said Justine Hendricks, FCC president and CEO, in a statement.
2024 (and an additional 73 under construction). Most (86 percent) serviced dairies. Digester adoption is highest in California, where 31 percent of the country’s operating digesters are located. An additional 11 percent are in
second-place Wisconsin. Despite growth, digesters still face obstacles, including regulatory hurdles and, in some contexts, a lack of economic incentives for producers to adopt the technology.
A private members’ bill introduced by Canada’s Bloq Quebecois was granted unanimous approval by MPs, resulting in a fast track to the senate. The bill, entitled the Act to amend the Department of Foreign Affairs, Trade and Development Act (supply management). The text states that the Act would have the following text added after subsection (2): (2.1) In exercising and performing the powers, duties and functions set out in subsection (2), the Minister must not make any commitment on behalf of the Government of Canada, by international trade treaty or agreement, that would have the effect of • (a) increasing the tariff rate quota, within the
Biopower specialists Weltec Biopower GmbH (Weltec) has expanded its global management team. In addition to current managing director Jens Albartus, Dirk Krumdieck and Tobias Gerweler (all pictured L-R) will also take on new management responsibilities. With an objective to efficiently manage an increasing number of orders and clearly structure responsibilities, the company says the new appointments are part of its strategic goals for the coming years. Gerweler holds a degree in mechanical engineering and has held leadership roles in industrial engineering. Krumdieck
meaning of subsection 2(1) of the Customs Tariff, applicable to dairy products, poultry or eggs; or
• (b) reducing the tariff applicable to those goods when they are imported in excess of the applicable tariff rate quota.
Despite its apparent unanimous popularity with MPs, some industry groups have been critical, such as the Canadian Agri-Food Trade Alliance. CAFTA’s release, following the passing in Parliament, criticized the lack of consultation, and stated it “undermines Canada’s reputation as a reliable trading partner… at a time of growing global uncertainty.” CAFTA criticized the bill as “protectionist.”
holds a degree in industrial engineering and has held previous leadership roles in sales and project management.
This is Part One of a two part series.
BY TREENA HEIN
In this first feature, we look at pyrolysis basics, the benefits of biochar in manure management and how two leading companies are addressing the main economic limitation. Stay tuned for Part Two in our September/October issue, where we’ll explore the exciting market potential for biochar, challenges to scaling up and what’s left to learn.
“It will not be easy, and there is a lot of hard work to be done, but biochar as an agricultural input is poised for rapid growth, finally.”
Many would agree with this statement from the April 2025 newsletter of the U.S. Biochar Initiative, with biochar now poised to
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make major impact. And one of its raw feedstocks is manure.
Biochar is a unique material that results from pyrolysis, a hightemperature process which acts on carbon-rich raw organic substances in a low-oxygen environment. Methanerich gas and bio-oil are also produced, which can both be used to make heat, electricity, gaseous fuel and more.
Biochar characteristics depend on the feedstock, but also the pyrolysis temperature (typically between 660ºF to 1,650ºF) and how long the feedstock is in the reactor.
Feedstock materials range from wood, crop debris and manure to biodigester digestate, human sewage
The Cornell pyroysis project, pictured above, uses the gases from the process to heat water, which dries incoming manure.
biosolids and food processing by-products – anything with lots of carbon will do. Compared to the raw version of these feedstocks, the biochar form offers many superior characteristics. With manure biochar for example, there’s little odor compared to raw manure. In handling and storage, compared to any raw material, biochar is porous, generally lighter in weight (with a density of only 5-12 lbs/ ft2) and stable (it does not readily decompose).
Because of its composition and porosity, it can also bind with various materials. For example, University of Nebraska-Lincoln scientists have found that biochar added to the soil in the pens at beef feedlot operations absorbs significant amounts of nitrogen, preventing some loss of that nutrient to the environment. (However, note that during pyrolysis, over half of the nitrogen in raw materials can be lost to volatization.)
Solid-liquid separation is already common in dairy and swine production for many good reasons. The solids can be used for bedding or applied to the fields, and due to their low weight, they’re more easily transported to areas far from the farm. But as Joseph Sanford at University of Wisconsin-Platteville has noted, converting solids to biochar can further reduce their mass by up to 80 percent. Unlike nitrogen, no phosphorus is lost in pyrolysis. In fact, manure biochar can have a P density six times that of the original manure. This mineral also remains stable in manure biochar in a form that’s better that other forms for crop absorption. Therefore, adding manure biochar to fields is much better in comparison to raw manure in terms of runoff of excess P (and N) into waterways. The carbon in biochar of any kind is also very stable, although
during pyrolysis, some of the carbon is lost to volatization, similarly to nitrogen, explains Jesper Knijnenburg at Khon Kaen University in Thailand, who with colleagues recently published an analysis of P dynamics in manure pyrolysis. The remaining carbon in the biochar, he says, becomes more stable through the formation of aromatic rings, a molecular structure resistant to bacterial decomposition, a process which results in CO2 emission. Thus, “some studies have demonstrated that the application of biochar to soils can have short-term effects,” adds Knijnenburg, “such as availability of nutrients and water retention, but also long-term effects such as increased soil organic carbon stocks.” A current study in Canada involves adding biochar to soil to aid in nutrient release management and reduction of greenhouse gas emissions.
Manure biochar is also already added to feed and livestock bedding in some parts of the world. Mahmoud Sharara at North Caroline State University and his colleagues have found that adding
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pyrolysis conditions.” And, contrary to the stability of N and P in biochar, there’s a lot of potassium release from biochar, which may be more pronounced at pyrolysis temperatures.
Pyrolysis also comes, of course, with capital investment in the reactor and operational costs as well. And the feedstock must be quite dry. Sanford has found for manure pyrolysis to make economic sense, dry matter content should be at least 70 percent. Liquid manure generally has only one to seven percent dry matter, slurry eight to 12 percent and semi-solid manure 13 to 19 percent.
All such costs are offset by the value of biochar as an input and the potential energy value from the gas and biooil. There’s also potential, note Knijnenburg and his colleagues, to use manure biochar in water treatment and construction materials. At the same time, they find there is currently “very high variability and uncertainty” in estimating the cost and benefits. Knijnenburg concludes in any cost/benefit analysis, “drying requirements for wet manures represent a significant cost consideration.”
Among the world’s pyrolysis technology companies are several that are taking drying costs of manure head on.
One is Biomass Controls of Connecticut. Its team recently partnered with Cornell University in a project at a New York dairy farm, where “our system uses the gases from the process to provide the thermal energy to heat water that is used to dry the incoming manure,” explains Biomass Controls CEO Jeff Hallowell. He adds that this setup includes “a catalytic emissions technology that uses a thermochemical process to combust the gases after the pyrolysis of the separated manure.” Biomass
Controls now has more than 25 other containerized pyrolysis systems of various sizes installed in the U.S., India and Africa, and all of them accept feedstock with more than 35 percent moisture. These include manure, human biosolids, algae and industrial food waste. Their largest unit can process up to eight tons of raw material per day.
This month (June 2025), the Cornell project is undergoing intensive study carried out by dairy tech consulting firm Newtrient. “We will look at durability of the equipment, ease of use, what moisture content of the manure solids is needed for effective system operation, and more,” explains Jeff Porter, the company’s technical consultant. Porter recently retired from the USDA-Natural Resources Conservation Service, where he served as the Leader of the National Animal Manure and Nutrient Management Team. “We will also compare the energy produced by the system through pyrolysis for manure solids,” says Porter, “versus anaerobic digestate.”
Another pyrolysis technology firm capturing gas from the process is Frichs Pyrolysis in Denmark. This month (June 2025), its first full-scale reactor becomes operational on a pig farm, with an annual capacity of 10,000 tonnes of dry matter. Later this year, a similar reactor will be commissioned at the chicken and crop farm of the company’s founders Lars Bojsen and his son
Dried manure being fed into the reactor as part of the Cornell project, which is currently undergoing intensive study by dairy tech consulting firm Newtrient.
Peter. Over the years, the Bojsens have looked at various ways to manage the manure generated by their 150,000 laying hens, with the farm having only 370 acres of cropland (and in a European political climate where there’s substantial pressure to minimize the environmental impact of manure).
A few years ago, they connected with a local manufacturing firm to designed a ‘flash pyrolysis’ system where materials are heated to 800°C for only two to three seconds. Frichs Pyrolysis is now at the commercialization stage, with plans to build more reactors in Europe over the next year or so.
The raw chicken manure must be dried down from 25 percent dry matter to about 85 percent. The dried litter is pulverized in a hammermill to achieve a particle size of 3 mm or less, so that the reactor is receives a consistent raw material. Straw is also pulverized and added to the reactor. “With its much-higher dry matter content, straw doesn’t need to be dried down as much as manure,” explains chief commercial officer Bent Plougstrup. “You also produce more gas with straw included and we want make a lot of gas.”
As mentioned, some of that gas is used to dry the manure and some power the pyrolysis itself. The rest can be used for on-farm
generators or be further scrubbed and enter the regional natural gas network. “Gas can be used in a variety of ways, whatever is needed or wanted, and you can also separate CO2 and methane,” says Plougstrup. “Another use is district heating or combined heat and power systems. Maybe you install a reactor near a water purification plant, where they can use the biochar, the heat and the power.”
Frichs Pyrolysis currently has two current research collaborations with scientists at the University of Southern Denmark. One is an investigation of using bacteria to combine hydrogen and reactor biogas to create CO2 and methane. The other is examining how adding hydrogen to the reactor biogas can achieve pure methane for the grid.
There are also other pyrolysis systems, reports Sanford, that have separate drying systems associated. “When we were working with one company, drying... was an additional fee,” he reports, “which was similar to the cost of manure biogas dryer. Additionally, most of the systems are designed for processing wood-based material where the moisture content can be much lower than manure, and so, some of these systems with dryers may still not be suitable for fresh manure solids without additional drying.”
Overall, Sanford cautions, “it’s important to understand what the system was designed to do. That said, farms that would be able to invest in this technology likely have drying capabilities already.” He concludes that while the manure drying aspect of pyrolysis is a limitation, “it is not an impossible hurdle to climb.”
Come back for Part Two, in which we’ll take a further look at manure pyrolysis economics and building the market for manure biochar. •
BY RONDA PAYNE
It’s called farmer’s gold for a reason. Long before liquid manure’s value was generally understood in terms of scientific benefits, farmers were applying it to fields to improve crop yields and vigor. The gold came from better results, and therefore more cash in pockets, at the end of the season and in seasons to come.
Although the practice of spreading liquid manure on crop fields is fairly simple and well-accepted, it is also deeply rooted in scientific principles that early agriculturalists didn’t know. This isn’t to say there’s a need to slip on an Einstein wig to get manure applications to optimal levels, but the wild-haired genius’s work in how light interacts with matter was a contributor to the development of liquid manure sensors. These sensors work with the inherent
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variability in liquid manure nutrient levels to help farmers achieve ideal application rates on any field.
At Ohio State University, John Fulton, a professor in the department of food, agricultural and biological engineering is helping farmers understand how liquid manure sensors optimize manure’s wealth of nutrients and bring greater robustness to crops without over-application.
“Farmers will know what nutrients are going into the field, as they go out into the field,” Fulton says of how liquid manure sensors benefit farms in on-demand settings.
Liquid manure sensors are mounted on the flow pipe after a hole has been cut in the pipe. As the manure flows across the sensor, it identifies the constituents in the manure and operators receive
There is a limited number of liquid manure sensor products on the market, one example being the John Deere Harvest Lab suite of products (computer interface pictured inset).
the information they need about nutrients being applied in the moment. This data allows for immediate changes in terms of manure application speed and rate to fit the field’s requirements.
“There’s a flow meter on the inline that measures the gallons per minute or the gallons per hour,” he says. “Knowing the flow in the sensor, I can estimate the pounds per acre of each constituent that’s being applied.”
Adding a liquid manure sensor to manure spreading practices is a matter of precision. Understanding the N, P and K values of the soil, as well as those in the manure being spread, to achieve nutrient levels that fit the crop is the holy grail for most farmers; almost the equivalent to how Einstein must have felt when he discovered the theory of relativity.
The manure sensor’s near-infrared (NIR) sensing estimates factors such as nitrogen, phosphorus, potassium, ammonia and other substances in the manure. Each material has its own band or region within the electromagnetic spectrum and by shining the NIR light on the manure, the reflectance determines which band (and therefore which nutrient) is present, and in which quantities, at any given time.
Currently, liquid manure sensors are able to measure nitrogen, potassium, phosphorus, ammonia, and dry matter.
“It does a really good job of detecting the dry matter or solids in that manure,” Fulton says. “The near-infrared looks at the percent reflected energy of those bands as it changes. It indicates the constituent of that manure.”
Soil sampling is the benchmark before nutrient application. Having that baseline gives a farmer their starting point. The levels of nutrients required for a successful crop come from understanding what is in place prior to application.
So, why not just take a sample of the manure as well? After all, one plus one equals two. But as Fulton explains, one isn’t always equal to one.
“Normally, we go out and take soil samples in the field in order to understand what the soil fertility levels are. Then we’ll take a sample in the [manure]
pit to know. Then I can calculate how much of that liquid manure I can put on the field, [considering] whatever the recommendations or limits are for that [region],” he says. “As I draw down the lagoon, it stays fairly even, but all of a sudden, it can jump up. If all of a sudden the concentration jumps up, I could overapply in that field.”
The majority of liquid manure sensors are being used on the pipes to take advantage of the ability to change the rate of application. However, there are options
for more static measures.
“Most of the people are using it out in the field. That’s where companies are selling them,” Fulton says. “That’s what most people are thinking about when they talk about liquid manure sensors. Now, there are also kind of desktop versions where you can just take a sample at a point out of the pit and measure that as well.”
Although this “snapshot in time” approach has value, the real benefit lies in seeing what the level of nutrients are
CONTINUED ON PAGE 19
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DAY ONE – JULY 30
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Purchase expo & tour tickets online
BY JACK KAZMIERSKI
Methane emissions are a global problem and a growing concern. Reducing emissions from dairy farms is a key piece of a bigger environmental picture as the livestock industry looks for ways to reduce the size of its greenhouse gas footprint.
According to a recently published study, Sulfate Additives Cut Methane Emissions More Effectively at LowerLiquid Manure Storage Temperatures, “the agricultural sector contributes to global methane emissions, and in Canada, approximately 29 percent of methane emissions were due to the agriculture sector.” The study was conducted by
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the Science and Technology Branch of Agriculture and Agri-Food Canada.
Part of the problem is what’s known as “enteric methane,” a by-product of the natural digestive process that takes place in ruminant animals, like cattle, and is naturally expelled by these animals. The other major contributor is stored manure, and according to this study, the latter can be addressed, “at low capital cost and in the near term.”
The study explains that manure stored anaerobically in tanks or lagoons creates an environment in which microorganisms produce methane. Furthermore, the production of methane becomes a bigger issue
The additive study, conducted by AAFC, was performed in a temperaturecontrolled environment.
in warmer weather. So, although methane production may not be an issue in the winter months, it is a major concern in the summer when temperatures rise.
According to this study, temperature and time play key roles in the production of methane. The higher the temperature, and the longer that temperature remains high, the larger the quantity of methane produced in the manure. Optimal temperatures for methane production are 25ºC and higher, and the study reports that as much as 87 percent of yearly methane emissions can occur in the span of only three warm months.
CALCIUM SULFATE
While there may be a number of ways to reduce methane emissions from stored liquid manure, the study reports that additives are likely one of the most effective, since this approach is potentially scalable, affordable, and flexible enough to work for a variety of farm sizes.
One of these additives is sulfuric acid, which has been reported to significantly reduce methane emissions. However, according to the authors of this study,
sulfuric acid presents potential health risks, which can only be mitigated with specialized training for handlers and careful storage. That’s why this study also looked at an alternative to sulfuric acid, namely calcium sulfate. Although not as effective, calcium sulfate “did show significant reductions in methane production when compared with the control.”
The study, conducted in a temperaturecontrolled environment, compared sulfuric acid and calcium sulfate to inhibit methane production at 18, 21 and 24ºC, representing summer manure temperatures on farms in different regions of Canada.
As expected, the experiment showed that methane production was highest at 24ºC, and lowest at 18ºC. “Temperature also plays a role in how often you need to apply the additive [sulfuric acid or calcium sulfate],” says Andrew VanderZaag, research scientist with Agriculture and Agri-Food Canada, and co-author of the study. “We’re trying to figure out what would be the right prescription in terms of how often you would need to reapply the additive in order to maintain a high level of efficacy over the warm season. We don’t have that information yet.”
What we do know, explains VanderZaag, is the warmer the weather, the more often farmers would have to reapply one of these additives. “So we know the direction, but we don’t know the exact details,” he says. “That’s what we would have to work out [by conducting this experiment] on a farm.”
Another reason testing these methanereducing additives on an actual farm is a logical next step, he says, is because temperatures are kept at a constant level in a lab. In the real world, they fluctuate hourto-hour and day-to-day.
One of the key findings of this study is that sulfuric acid is, as expected, more effective at reducing methane production than calcium sulfate. Moreover, sulfuric acid offers another benefit. “We didn’t address this in the study,” says VanderZaag, “but sulphuric acid reduces the pH [of the manure], which decreases the loss of ammonia into the air. So that’s a co-benefit, which you’re probably not going to see with calcium sulphate.”
While the study proved sulfuric acid and calcium sulfate can effectively cut methane emissions, farmers may wonder if this is
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cost-effective. “I think so,” says VanderZaag. “There’s an existing supply chain for fertilizer, and for certain industries sulphuric acid is a fertilizer. And gypsum is used for many things, like drywall, so there’s a supply chain there that can be tapped into.”
The question is how much sulfuric acid or calcium sulfate a farmer would need to have a meaningful impact on the amount of methane their stored manure generates? That number, unfortunately, is something that this study can’t conclusively determine.
There are variables, says VanderZaag. “First, you don’t need to treat manure yearround – only in the few summer months, and maybe early fall when the temperature in the manure is above the threshold of 15ºC.” VanderZaag specifies 15º because according to the study, “there is evidence to suggest that little methane is produced at or below 15ºC.”
Furthermore, he says in colder parts of the country, additives may only be needed for between two to four months because the manure won’t stay above the 15ºC threshold for longer periods of time.
The other variable that will impact the amount of additive is the quantity of
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Lab gas calcium sulphate and manure used for AAFC’s comparative study of additives.
manure they have in storage during the time of the year when manure temperatures would rise about the 15º threshold. “It’s the amount of manure in storage during the warm part of the year that matters. That’s what has to be treated,” says VanderZaag. He explains this study looked at liquid manure, specifically, because solid manure isn’t a major concern, when it comes to
methane emissions.
In addition, although the amount of methane that may be produced in manure from different animals, like swine or cattle could vary, “in general, there are a lot of similarities,” he says. “The biology and the methanogens that are actually producing the methane, are going to be there in both cases, so in broad strokes, I would say the two are similar.”
Solid manure, adds VanderZaag, is more complicated. “The greenhouse gas budget is partly from nitrous oxide, partly from ammonia and partly from methane,” he says. “You have to address them all together, otherwise if you decrease one, you increase another. With liquid manure, we can focus on just the methane.”
The findings in this study are based on adding roughly two grams of additive to a liter of manure. “That translates to about 2kg per cubic meter, or per ton of manure,” says VanderZaag. “It’s a similar rate for both sulfuric acid and calcium sulphate.”
Although this formula produced favorable results in a lab setting, VanderZaag admits we can’t be sure if this ratio would work at scale in a farm setting. “What we saw is that regardless of the temperature, we could get a 50-60 percent reduction [in methane] with calcium sulphate, and a 70-80 percent reduction with sulphuric acid.” That said, this was not a one-and-done approach, he explains. “We had to add more [sulfuric acid or calcium sulphate] after a period of time,” he says. “At 24º, we had to add it again after about a month, while at 18º the [methane reducing] effect could last several months.”
In other words, the lower the temperature, the less often either additive has to be mixed into the manure. “If the temperature is cooler, you don’t have to reapply very often,” he says. “You might only need to add it once for the warm season, whereas at a higher temperature, you might need a higher dose or a higher rate, but we don’t know that yet for sure.”
While this study is encouraging, VanderZaag says replicating these results in the real world is a must to see how these additives will work on an actual farm, and to determine if the application is scalable.
“The full farm-scale study... is what we would like to do in the near future, and we’re applying for funding to do that.”
in “real time,” he says. “As a farm operator, if I see those rates change, maybe I need to make an adjustment.”
This can include changing the rate of flow on the pump or changing the speed of the tractor.
“Basically, I’m reducing the rate at which I’m applying,” he says. “If it starts high and then starts to drop, I might be able to slow down or adjust the pump speed.”
Fulton notes that John Deere, CNH Industrial and Zunhammer all have liquid manure sensors field ready, but he cautions there are considerations before pulling out the checkbook. The first, and perhaps most important, is to ensure the technology will work with existing farm equipment.
“Most of the sensors are only going to work with newer technologies,” Fulton says. “Farmers have to be up-to-date on more modern or newer displays on the tractors. They’ve got to have the integrated screens and then it has to be one of the more recent versions with capabilities built into it.”
Checking compatibility or upgrade options beforehand will make the difference between money wisely spent to make more money and a costly path of purchases and modifications to make existing tools adapt. Calibration is another consideration. Fulton says most of the sensors have some calibrations built into the systems, but be prepared for a time investment to collect samples, run lab tests, compare and adjust. Each farm is unique and so is the manure it uses.
“They have to be calibrated for the various types of manure
that are out there,” he says. “You could have dairy, you could have beef, you could have swine. Some farmers even mix those. Nutrition fed to the animals influence those calibrations. In Europe, they’ve done a really good job of calibrating. But even so, they’re not absolute. But it gives you a close estimate and tells you when things significantly change.”
Mounting the sensor itself doesn’t require much in the way of modification. Retrofitting to existing pipes is easy with only a hole and mounting of the sensor required. “As long as it’s liquid manure, I would assume either the farmer, or the custom applicator, they would have the right equipment,” he says. “Most of your tankers… they can be retrofitted. Or a drag line.”
The benefits of using a liquid manure sensor during application are numerous with scientific data topping the list.
“Number one, it gives that feedback to understand as you’re pumping down a pit, what the relative concentration of nutrients is in the manure,” Fulton says. With this comes the ability to make changes to the rate of application on the fly.
“Because of that, we’re being better stewards of the environment because we’re eliminating conditions where we’ve had run-off or excess levels of nitrogen or phosphorus,” he says.
Plus, with each application comes a long-term record of application that shows how much of each nutrient was applied where. This data also informs future decisions in terms of field management for future applications.
Simpler methods of applying science to agriculture can improve the transformation of manure into farmer’s gold. •
Aerobic composting thrust into the research spotlight
BY TREENA HEIN
Today, anaerobic digestion provides a proven way to value-add to manure, which of course is already a highly valuable commodity by itself. There are about 400 manure digesters in the U.S., mostly using dairy manure, but also swine, poultry, and beef manure, with hundreds more in Europe and other locations around the globe. Biogas from the process can generate electricity and/or heat, and can power vehicles as well, all while reducing farm GHG emissions and providing digestate to use as fertilizer or bedding. This provides revenue for farmers once ROI is achieved.
Digesters come in full-sized and mini models but generally make more economic sense for large operations because of the capital costs, but also the need to manage the anaerobic process effectively for sufficient ongoing gas production.
But what about the aerobic process? We all know that aerated manure composting provides a huge amount of heat. Simple but innovative systems to capture that heat can be built and managed easily and cheaply. This makes them very
ABOVE
well suited for the many smaller farms of New England, other similar regions of North America, and beyond.
“Comparing the two ways to harvest energy from manure, anaerobic and aerobic, digesters are known about but not common, but systems that harvest energy aerobically, what we are doing, they are very rare globally,” says Sazan Rahman, assistant professor and controlled environment agricultural researcher at the University of New Hampshire (UNH).
Rahman and one of his graduate students, Hafizur Rahman, have recently designed two heat capture and transfer systems from composting manure, with a comparison of their performances to start this coming winter at the UNH Woodman Horticultural Research Farm.
Hailing from Bangladesh, Sazan Rahman did his masters in mechanical engineering and Ph.D. in bioresource engineering degrees in Canada, investigating how to optimize the energy consumptions in controlling the heating,
One potential outlet for heat generated from manure could be a farm in New Hampshire with an onsite greenhouse – potentially supporting year-round vegetable production.
ventilation and air conditioning for agricultural buildings and how renewable energy sources like geothermal, solar and manure can be integrated into those controlled environment agricultural systems (greenhouses being the main example). He started at UNH in mid-2023 and had discussions there with John Aber, who has since retired but had studied how biofilters can be used to reduce gases such as ammonium from composting manure, allowing the warm air from the composting process to be safely used. Aber had done his research at UNH’s Organic Dairy Research Farm, where the Joshua Nelson Energy Recovery Compost Facility was built in 2013. The system uses a heat exchanger, enabling heat from the composting manure to warm water that’s further heated and used for cleaning and sterilizing milking equipment.
“I also started reading papers and looking at ideas and secured a grant from NH Agricultural Experiment Station that allowed a graduate student to work on the project,” explains Rahman. “There is so much potential to use manure in this way, in this region and other similar regions. Only 6,329 out of 30,717 farm in New England’s six states apply manure to the field, mainly because of risks related to pathogenic bacteria. So, there is a huge amount of energy going to waste. Instead of letting that happen, you can build simple, low-costs systems that can capture and use that energy for many uses, including food production.”
IMAGINING THE POSSIBILITIES
One scenario to use the heat could be a farm in New Hampshire where the farmer constructs a commercial greenhouse on site. And while yes, there’s a substantial capital cost to that, if heat
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from the farm’s manure can support year-round production of vegetables, ROI on capital costs can be achieved relatively swiftly, with operational costs minimal. There’s little or no natural gas needed to heat the greenhouse, so environmental impact is minimal. In addition, the farmer has another source of income, local food production is boosted, and more manure (in safer, composted form) can be used to fertilize field crops.
But existing greenhouse operations near farms could also use manure heating during the cold months of each year. Again, like a greenhouse on a farm, avoiding the use of natural gas would be a huge savings and slashes the environmental impact of greenhouse food production. Rahman adds that the manure in either scenario is only composted for seven to 15 days, and in this second scenario, “it can be returned to the farm as fresh manure is picked up. There would be a cost for manure transport, but that might be shared by the farmer and the greenhouse operator. We will look at all the economics as the project progresses.”
But there’s also the value of composted manure. While much of that value depends on composting expertise and manure type, the high temperatures during composting destroy bacteria such as E. coli, and species of salmonella and campylobacter that are a concern with the application of raw manure to fields. The heat during composting can also kill weed seeds that may be present. Composted manure generally has a more balanced nutrient profile (although typically lower in nitrogen) than raw manure, releases nutrients more slowly and smells a lot less. Composted manure can also enhance soil structure and soil moisture retention compared to raw manure.
As mentioned, Rahman and his graduate student, Hafizur Rahman will be testing two heat capture systems. One involves ‘compost air’ warming a 1000-liter water tank with an adjacent heat pump that distributes heat to the greenhouse. “The induction side of the coil is against the tank, and the other is in the greenhouse,” explains Rahman. “The heat from the coil radiates into the greenhouse environment, and fans constantly circulate that heat through convection.”
The second system directly circulates warm compost air into the greenhouse after gases like ammonium are greatly reduced. This involves a proprietary system that has another function as well. “We also need to dry the air,” Sazan Rahman explains. “The air in greenhouses is already very humid, so we’ve designed a system that results in both dry and clean air.”
Both systems will use manure from the UNH Fairchild Dairy Teaching and Research Center and the UNH Equine Center, blended with waste hay. Rahman explains that cattle manure is very dense and hard to aerate, and without aeration, composting will not occur. Adding horse manure with the bedding mixed in makes the resulting blend more porous. “Horse manure also has a lot of fiber in the form of lignin and a higher content of other materials that enhance microbial activity to a small amount,” says Rahman. “Adding it enables constant heat from the manure composting process and also keeps heat production going longer.”
Over the coming winter and for two more after that, Rahman and Rahman will evaluate and compare the heating efficiency and economics of the two systems (the greenhouse is being partitioned). They will also analyze the crop (hydroponic lettuce
in this case) in terms of yield and quality. Automated monitoring systems in the greenhouse and the compost pile will collect data on heat output, air quality and other parameters.
However, there’s some preliminary data from this past winter on temperature, air quality, and heat output that Rahman will present at ASABE 2025 in July (the conference of the American Society of Agricultural & Biological Engineers). “We will also seek feedback from the experts in attendance that will assist us to fine-tune the systems,” says Rahman.
The aeration of the compost piles will be achieved through air fed through perforated pipes underneath. “Aeration can also be accomplished with manual turning of the compost, but that adds complexity,” says Rahman. “We also don’t want a system that needs high air pressure, which would mean a lot of ventilation horsepower/energy consumption.” To make aeration through perforated pipes and regular fans work, as mentioned, the material to be composted needs to be good and porous, but it must also be arranged in layers. While the design is proprietary, Rahman can say that it’s an open system with fresh air constantly being introduced into the manure.
An open system does mean that not all the heat from the composting manure is captured, but Rahman explains that if you try to capture more heat through using an enclosed bin system, aeration becomes an issue. In addition, using a compost pile with fresh air constantly being introduced also means that the airborne bacteria in the warm ‘compost air’ is kept at a low level.
Regarding challenges before the trials start this fall, Rahman lists the biggest to be how to best protect the composting manure from rain and snow. “We’re looking at various ways to cover it and insulate it to some extent,” he says, “but we know that in the cold winter temperatures, to keep a large amount of heat being generated from the composting process, we’ll need to introduce new manure frequently. We have to balance the quality of the warm ‘compost air’ with the need for continuous aeration, but we also have to keep the composting process going at a high rate, at a high temperature. We have to look at the heat that the
greenhouse needs, how much heat the composting can produce, and how much is lost from the system. Producing 1.7 times the heat that’s needed is generally the safety factor.”
But no matter how fast the progress on these compost heat systems, there are bigger plans afoot. Rahman envisions fully sustainable greenhouses that integrate composted manure heating with other renewable energy sources like solar and geothermal, enabling farmers to produce food with minimal energy use.
“The aspect that’s most exciting is making this work as cheaply as possible so that we can benefit livestock and greenhouse farmers,” he says. “You don’t have to spend a lot of money, just set up a system with some pipes and fans. You get manure from local farms, you use the heat from composting it and the farm gets composted manure back, which is safer and better than raw manure to spread in the fields. There is also more local food and less environmental impact, so it benefits everyone.” •
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Researchers and students at Michigan State University’s College of Agriculture and Natural Resources (CANR) have a new treat to look forward to.
The new T6.180 methane tractor from New Holland, which parent company CNH claims is the world’s first 100 percent methane-powered production tractor, will be utilized for educational and research purposes at locations throughout the campus, including the MSU Agronomy Farm, Dairy Cattle Teaching and Research Canter and the south campus farms.
This means those students and researchers will get access to the rare piece of equipment, while further solidifying CANR’s commitment to agricultural innovation. As an added bonus, the tractor will be powered by refined gases produced at MSU’s own anaerobic digester, offering CANR a chance to show the “full-circle” benefits of renewable natural gas.
The tractor was unveiled May 7, at the MSU Innovating with Dairy Symposium. Its key benefits include:
• Producing 98 percent fewer overall emissions compared to European Stage V emission limits;
• A 10 to 15 percent reduction in CO2 emissions when using biomethane;
• Energy self-sufficiency; and
• Cost efficiency (an estimated 30 per cent reduction in running costs).
Under the terms of the partnership with CNH, CANR will have cost-free access to the New Holland T6.180 Methane tractor for one year, creating opportunities for students, researchers and the public to see end-to-end methane tractor ecosystem at work in the field.
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Nitrogen in manure is like a cat with hundreddollar bill in its mouth: very valuable, but hell-bent on escaping (especially when doused in water). While a crucial nutrient for crop production, it also has the most loss pathways. Keeping nitrogen in the field where it’s applied is economically beneficial and ecologically vital to minimize pollution risk.
Manure supplies two forms of nitrogen: ammonium (inorganic) N, that is immediately plant-available, and organic N (sometimes referred to as “slow release nitrogen”), which needs to be broken down into ammonium before it can be taken up by plants. Manure from monogastric animals, such as swine, tends to be high-ammonium, containing more ammonium nitrogen than organic nitrogen. Ruminants, such as cattle, are the opposite. When manure is left on the soil surface, ammonium rapidly converts to ammonia gas and is lost to the atmosphere through volatilization. If you surface-apply a high-ammonium manure and don’t incorporate within four days, expect to lose around half of the total nitrogen this way. The organic N portion will remain, but a 50 percent reduction in overall nitrogen is significant. In this situation, manure with less ammonium would lose less total nitrogen to volatilization.
Nitrate is another important soil-nitrogen form that gets a lot of attention – rightfully so, as it’s the
called denitrification. Ammonium is only one step away from nitrate; if nitrification conditions are right, large amounts of nitrate may form with highammonium manure. In contrast, organic N is two steps away from nitrate as it must first be mineralized into ammonium, then turned into nitrate through nitrification. So while high-organic N manure can still present nitrate problems, those challenges are more delayed with better odds that a plant will use that ammonium before it can become nitrate.
Whether you use tillage or injection, get the manure under the soil surface ASAP after application. The more time between surface application and incorporation into the soil, the more ammonium will be lost to the atmosphere; incorporation within 12 hours is recommended. Injecting liquid manure will also minimize volatilization losses due to no time on the surface. Apply in the spring, or sidedress in the summer. This minimizes the length of time manure sits before being used by plants, meaning less time for ammonium to convert to nitrate and be lost. Studies in Ohio and Minnesota have shown using a dragline and injecting manure before the V5 growth stage in corn can be a viable sidedressing option. Apply to a growing crop whether it’s a cover crop, perennial, or pasture. This can preserve nitrogen through plant uptake and reducing surface runoff and erosion.
Keeping nitrogen where it’s applied is vital to minimize risk.
nitrogen form most easily lost to the environment. Manure does not supply nitrate directly, so don’t bother paying extra for the nitrate test at the testing lab. Does that mean manure producers don’t need to worry about nitrate? No. Ammonium N in manure transforms into nitrate once in the soil. The process is fittingly called nitrification. Since this is a microbially driven process, the rate at which nitrification happens is greatly affected by moisture and temperature, and therefore, tricky to predict. Nitrate is easily dissolved and will travel readily with water; whether that is runoff into ditches and waterways, or leaching downward into groundwater. Nitrate can also be lost as a gas through a process
Compost the manure. Organic N is the primary nitrogen form of properly composted manure and is less susceptible to loss until it transforms into ammonium and nitrate. For fall applications, wait until the soil temperature is below 50ºF Since nitrification is a biological process, waiting for cool soils will slow down the conversion to nitrate. What about nitrification inhibitors? Do nitrification inhibitors work with manure? Sometimes, and it depends. Research on this topic has given mixed results that are sometimes conflicting. But most studies agree that the same benefit from inhibitors can be achieved by simply waiting for cool soil temperatures before applying in the fall.
If you do use these products, remember that they are not a silver bullet and will wear off over time.•
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