Dealing with manure is part of the daily grind on any dairy farm. It’s a crappy job, but when managed properly, manure can be an extremely valuable resource. Many farms now collect and store manure systematically, and a growing number are exploring composting, separation or digestion. But before jumping into any new system, Dr. Rebecca Larson, professor and Extension specialist at the Nelson Institute for Environmental Studies, says producers need to define their goals.
Start With Clear Goals
“Start by asking what you want to change,” she says. “Do you want to reduce hauling costs? Manage phosphorus? Reduce odor? That clarity is key.”
Larson emphasizes evaluating your current system from barn to field. Before considering upgrades, it’s important to understand how your system functions, where the bottlenecks are, and how manure moves through your operation.
“Even knowing how many truckloads you hauled last year, or where and when, can make a big difference,” she says. “That kind of information helps size a system, estimate cost and identify where improvements would matter most.”
She also recommends having a rough idea of your farm’s manure characteristics, such as consistency, water content and nutrient profile. These influence which technologies are feasible, how systems perform and what adjustments might be needed to get the most value.
“Some systems just don’t work if your manure is too dry or too liquid,” she adds. “That’s why I recommend drawing out a manure flow diagram. It helps you visualize the full system and your weak spots.”
Storage Matters
Well-designed storage gives farms flexibility to apply manure when conditions are best, not just when forced. That means better nutrient retention, less runoff and fewer weather-related headaches. Properly sized storage also supports labor efficiency, better planning and improved integration with advanced systems.
“Most people build storage because they’re required to,” Larson explains, “but it really gives you flexibility, especially during winter.”
Composting: Simple and Scalable
Composting is a popular option due to its simplicity and multiple benefits. Chryseis Modderman, Extension educator at the University of Minnesota, explains that high temperatures and aeration kill most pathogens, making composting an effective way to sanitize manure.
“A compost pile made of manure, bedding and other organic material can reach up to 150°F, sufficient to destroy most harmful microbes,” Modderman says. She recommends two heat cycles of at least 131°F, with aeration and uniform heat distribution, to fully break down the material into a stable, soil-like product.
Storing manure under anaerobic conditions can also reduce pathogens. “Though some bacteria can survive anaerobic conditions, most pathogens will be killed within 30 days,” Modderman notes.
Benefits of composting include reduced volume, odor and pathogen load.
“You can cut your manure volume nearly in half,” Larson adds. “It also kills weed seeds and creates a more stable product. Some farms market their finished compost, but this requires additional time and effort.”
Digestion: Powerful but Pricey
Anaerobic digesters break down manure without oxygen, producing methane that can be used for electricity, heat or renewable natural gas. Their popularity is rising as farms seek ways to generate energy, lower emissions and reduce odor. Daniel Ciolkosz of Penn State Extension notes that digesters also reduce the smell tied to land application, an increasing concern as more homes are built near farms.
“An anaerobic digester is an excellent addition to a manure management system for the reduction in near odorless effluent for spreading on fields,” Ciolkosz says.
The best digester depends on a farm’s manure system and location. Scraped, flushed or belt systems affect solids content entering the digester, which influences efficiency. In warm climates, covered lagoons are a lower-cost option. In colder regions, complete mix, plug flow or temperature phase digesters are more common due to better heating potential.
However, digesters come with a high price tag. Installation can run into the millions, especially when paired with gas upgrading or power generation equipment. Ongoing maintenance, oversight and permitting also add to the cost. These investments often require grants, partnerships or revenue from energy credits to make them viable.
Separation: Targeted Tools for Better Control
Separation systems are another tool producers should consider when evaluating long-term manure management strategies. These systems divide solids from liquids, helping reduce manure volume, improve nutrient management and enhance the efficiency of downstream processes like composting, bedding recovery or anaerobic digestion. They can also reduce storage needs and help tailor nutrient application to crop demands.
“From there, you can manage each stream differently,” Larson says. “It’s great for targeting nutrients, reducing hauling costs or recycling bedding.”
Screw presses are a common form of separation and cost about $100,000. Centrifuges are more effective for phosphorus but can cost up to $500,000 and require more maintenance. Multiple systems can also work in series.
“You might start with a screw press, then use an incline screen or centrifuge,” Larson adds.
Each nutrient separates differently. Particle size, solubility and system type affect how much nitrogen, phosphorus and potassium end up in the solid or liquid fraction.
“Ammonia stays in the liquid, phosphorus goes with the solids. If phosphorus is your goal, choose a system with high phosphorus efficiency,” she advises.
Separation also shifts nutrient ratios.
“Manure might start with a 3-to-1 nitrogen-to-phosphorus ratio. After separation, liquids might be 4-to-1, solids 1-to-1,” she says. “That allows for more targeted nutrient application.”
Many farms also reuse separated solids for bedding.
“And modeling shows separation systems may cut greenhouse gas emissions more than digesters,” she adds.
Advanced Options: Struvite, Biochar, Clean Water, and Pelleting
For producers looking to advance manure management, several emerging technologies go beyond basic separation. These tools help recover nutrients, reduce emissions and manage water, which is especially useful for large farms or those with limited land.
- Struvite systems extract phosphorus as a dry, dense product that’s easier to transport and apply.
- Biochar, made by pyrolyzing manure solids, holds water, stores carbon and can reduce harmful gases in digesters.
- Clean water systems use advanced filtration to recover 50% to 65% of manure as potable water. “I’ve actually drunk the water, and it’s clean,” Larson adds. These systems are gaining traction even in water-rich areas.
- Pelleting systems densify nutrients into transportable pellets, mostly seen on farms with 15,000+ cows.
Fit the System to Your Farm
Ultimately, effective manure management depends on clear goals and solid infrastructure. Taking time to evaluate your current system and choose the right tools can lead to better efficiency, fewer headaches and stronger returns over time.
“Manure processing can be fantastic, but only if it fits your goals, scale and management style,” Larson adds. “Sometimes the biggest gains come from small improvements. The more you understand your system, the smarter your decisions which benefit your farm, your finances and the environment.”
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