Manure handling has always been challenging. It is becoming even more so thanks to climate change, societal concerns, regulations, and economics, according to Peter Wright, an agricultural engineer with Cornell University’s PRO-DAIRY team in Ithaca, N.Y.

Wright detailed strategies for managing these challenges with technology during a “Technology Tuesday” webinar hosted by Penn State. He emphasized the importance of assessing options because there are opportunities to both treat manure and apply it in the field.

He urged dairy producers to “know and control costs” and keep in mind that they are not stuck doing what they are now. Evaluate the current approach, identify areas for improvement, and be willing to pivot.

The goal is a balanced system in which equipment matches the needs of the farm. This could include the use of custom applicators. Additionally, some dairy farms may benefit from added-value opportunities, such as carbon credits, renewable energy sales, and carbon footprint documentation into the supply chain.

More storage is always better

Undoubtedly, climate change is reshaping the way farmers conduct business. Wetter winters, drier summers, fluctuating temperatures, and intense storms in the Northeast make it difficult to store and spread manure. Environmental concerns, especially about water quality, further complicate manure management practices.

In New York, winter spreading and adverse weather application guidelines are now in place after a series of severe storms and winter melts in 2014 led to manure runoff into several freshwater lakes. To protect water sources, comprehensive nutrient management plans on concentrated animal feeding operations must now ensure no discharge will occur during a 100-year, 24-hour storm event and identify low-risk fields for emergency manure application. Many other states have also banned or restricted winter spreading, and restrictions for fall spreading could be on the horizon.

The rationale for long-term manure storage is rooted in efficiency and effective soil management. Rather than hooking, unhooking, and cleaning the spreader every day, manure can be hauled to the fields all at once in seasonal weather. Nutrients are better utilized in the spring and summer when plants are growing, and soil compaction is avoided from equipment tracking on wet fields.

In an ideal world, you have sized the waste storage pond correctly based on the comprehensive management plan and emptied it according to that plan, noted Wright. You have maximized the nutrients going on the fields to meet crop demand and prevented a build-up of solids. You controlled both the drainage area and the production of manure.

Actual management can look far different. Farms often build storage based on what they can afford and run into labor peaks at the same time storage needs emptying.

A farm that needs 12 months of storage but builds on a six-month budget is in trouble if it can’t get it emptied in the fall and then runs into a wet spring, remarked Wright. A farm may also struggle to follow the plan if equipment is not ready, labor is unavailable, or the weather is inclement. Nutrients are wasted, solids accumulate, and the potential for manure runoff increases.

An often-overlooked storage stress comes from greater manure production. An obvious surplus comes from having more cows on the farm, noted Wright. But manure volume also escalates as milk production rises and cows are fed more forages and grains.

“For all of these reasons, I think we are going to head into a scheme of more and more storage,” Wright noted.

Storage capacity that enables farms to spread in the summer has the bonus of applying manure to growing crops or when planting cover crops, which is a more efficient utilization of nutrients. There is a significant reduction in greenhouse gas (GHG) emissions when manure is not stored during the warmer, more biologically active months as well. The downside is odor, which may be eliminated with innovations in equipment and manure treatments.

Some farms may also be able to utilize frost tillage with low snow cover and 2 to 3 inches of frozen soil. Through capillary action, water is drawn up to the frozen soil and the soil underneath is relatively dry.

“The equipment rides on top of the frozen layer so there is no compaction,” said Wright. “You bust through it and inject (manure) into the dry soil underneath.”

Though it is a specific weather event that cannot be counted on, it does provide a window of opportunity.

Not in my backyard

Community concerns also complicate manure management. As more urban citizens move to rural areas, they become more vocal about manure storage. Safety and pathogens are frequently cited as issues, but the primary motivator is odor.

Public relations are key, so it is important to consider manure storage options thoroughly, commented Wright. Nobody wants to look at or smell manure storage, so choose sites where people can’t see them or create screens to block the view. Consider prevailing winds to ensure minimal impact when spreading manure.

“More farms are turning to satellite storage because it makes a lot of sense,” noted Wright. Often, they are closer to fields in which nutrients will be recycled, can be situated on land more suited to storage, and are less hemmed-in than facilities at the farmstead.

“I have learned over time that the access road is important,” Wright remarked. Originally, people wanted to put them close to the road for access and easy loading and unloading. But moving them back away from a public road out of sight is a better idea. Remote access also poses fewer safety issues as farm equipment enters and exits the satellite location.

Housekeeping is another aspect of neighborly relations. Keep manure handling equipment and storage areas clean. When you spread manure, keep the roads clean, too. Mud is often interpreted as manure, so mud that is tracked out and not cleaned up becomes a public relations problem.

Protecting water downstream

To ensure spillage at the storage site doesn’t drain into the clean water system, pay attention to loading and transfer areas. Evaluate surface flow and slope the loading area back to the storage if possible. Enclose the area and use a pump to direct dirty and clean water appropriately. At satellite locations, consider the distance to a road ditch and what can happen if things go wrong.

Farms can also protect water in ditches and streams by managing subsurface tile drainage with a water control structure on flat fields that adds to or reduces the water table. After harvest, the outlet is raised to increase the water table and reduce nitrate delivery during the off-season. It is lowered before planting to allow the field to drain and then raised after planting to store water while crops are growing.

Another option for the water control structure is a bioreactor that diverts water to an underground carbon source, like a bed of wood chips. There it converts nitrate nitrogen to harmless nitrogen gas.

A saturated riparian buffer offers a similar solution. Drainage from the edge of the field is spread out longitudinally through a series of trenches where nitrogen is reduced by vegetation and soils before water flows to the waterway.

Farms should also develop a manure spill response plan that anticipates how to handle emergencies.

An asset or liability?

Manure can be regarded along a spectrum ranging from worthless to a significant source of phosphorus, nitrogen, and organic matter depending on the circumstances. The perception of its value is largely dictated by the cost of spreading manure.

Wright examined this cost on farms in New York and discovered a range of about $30 per cow per year to about $325 per cow per year. Higher costs were generally associated with smaller herds doing daily spreading. However, the largest herds had slightly higher costs than mid-sized herds, likely due to longer transport distances.

Wright also looked at the per-cow cost of hauling methods for small and large herds. For herds with 50 cows, 5,000-gallon tankers are far less expensive to operate than owned drag hoses, hard hoses, and center pivots regardless of distance, ranging from about $80 at 0.5 miles to about $110 at 4.5 miles. For herds with 2,000 cows, a drag hose was the winner at all distances, ranging from about $30 at 0.5 miles to about $50 at 4.5 miles. A center pivot was marginally higher at all distances.

A hard hose ranged from about $52 at 0.5 miles to about $95 at 4.5 miles. Tanker costs were about $30 at 0.5 miles and spiked dramatically at 1.5 miles. Each farm needs to calculate their own costs.

To improve the bottom line, farms may use custom applicators. They can spread the cost over more cows and operate less expensively.

Factors that contribute to spreading costs go beyond herd size, method and distance and vary greatly from farm to farm. Field size, gallons spread per application hour, and efficiency also impact costs.

“Some of the variables you can’t change, but some you can,” Wright said. Take a close look at what you are doing because small changes can make a huge difference in what it costs to spread manure.

Farmers can learn more using a manure value calculator developed by Cornell. The tool can help determine fertilizer equivalent value, break-even hauling distances, and equipment operating and ownership costs. Find it at bit.ly/softwarecalculators.

Storage cover opportunities

In the future, farms may be encouraged to cover manure storage to reduce GHG emissions. Storage covers are also a means of reducing manure storage needs. Because solid-liquid separation is required for this setup, the volume of solids will be reduced by about 20%, and precipitation — a significant chunk of the waste storage pond — will be eliminated.

They are expensive, though, and the cost generally cannot be recouped without a grant or the sale of carbon credits. Dairy producers can assess the viability of an impermeable flexible cover and flare system with a worksheet developed by Cornell, which can be found at bit.ly/environmentalcalculators.

Over time, systems to treat manure will get more sophisticated and complex. Anaerobic digestion is a wonderful addition to the mix because it homogenizes manure effluent so it can be treated more effectively, reduces odor and pathogens, improves water quality, and yield renewable energy.

There are countless ways of putting one of these systems together based on bedding type, manure gathering and conveyance setups, treatment system, storage, and desired output. Newtrient has developed a solutions catalog to help dairy producers evaluate technology for these systems. It can be found at www.newtrient.com.

Anaerobic digesters can also help dairy farms deal with environmental concerns about GHG emissions. By capturing these gases, farms can not only reduce atmospheric emissions but also earn revenue from the sale of renewable gas or carbon credits.

By installing an anaerobic digester, dairy farms could potentially cut GHG emissions in half. Wright estimated that the “typical” New York dairy farm releases four metric tons of CO2 equivalents from long-term manure storage each year. Fossil fuel use for electricity was estimated at 0.58 metric tons of CO2 equivalents per cow per year.

If you put in an anaerobic digester, capture methane, and produce energy, you will wind up with very different results, he noted. The four metric tons of CO2 equivalents will be offset by renewable energy production (typically about 2,000 kilowatts per cow per year), dropping effluent storage emissions to about two metric tons of CO2 equivalents per year.

While there is a significant social cost of carbon saved and energy value, your ability to capitalize on that depends on your situation and location, Wright summed.

Always think safety first

It is important to consider the safety of both people and animals around manure storage. Stored manure generates highly toxic hydrogen sulfide and other gases like methane, ammonia, and carbon dioxide. Be especially careful if you use gypsum bedding because it contains high amounts of sulfur.

Toxic gases can be released during agitation, so keep everyone at a safe distance. When agitating an underfloor pit, provide maximum building ventilation. If human entry is necessary for a rescue situation, use a self-contained breathing device and the buddy system. No matter how manure is stored, transported, or applied, safety must always be top of mind.

This article appeared in the August 2024 issue of Journal of Nutrient Management on pages 20-22. Not a subscriber? Click to get the print magazine.