A livestock farm of any size must consider how to handle the manure produced by the animals raised on the property. By default, smaller farms will have less volume than large operations, but both should be equally committed to creating and following a manure management plan. A well-executed manure management plan allows any farm to obtain the full value that a crop nutrient such as manure can provide while protecting water, air quality and staff.
“Manure gives off nutrient emissions like nitrogen, phosphorus and greenhouse gases, which are a nuisance to the environment,” said Victor Cabrera, Associate Professor and Extension Specialist in Dairy Farm Management, University of Wisconsin-Madison.
With increasing concerns for environmental conservation, manure management plans for livestock farms of all sizes are critical. Several types of manure management strategies often depend on the size of the farm, type of livestock and state regulations.
Composting is one manure management practice growing in popularity. While composting offers many benefits, including destroying weeds and pathogens and stabilizing nutrients as organic compounds, if not handled properly, it can create runoff that can affect ground water.
Large farms with herds producing significant volumes of manure dictate the need for a manure storage system such as a lagoon, pond or pit. Designed to hold manure until it can be spread on fields, the deep holding areas can pose several hazards to humans and livestock.
Pit or covered storage systems can create a buildup of toxic gases including hydrogen sulfide, ammonia, carbon dioxide and methane. The most deadly gas, hydrogen sulfide, smells like rotten eggs and is heavier than air. In high concentrations it is fatal to humans and animals in a few seconds. Stored manure also emits ammonia gas, which smells like bleach. The alkaline gas can cause burns in the eyes, throat and lungs.
Manure also gives off carbon dioxide and methane gas; both are odorless and require detection or monitoring equipment to detect the gas levels present. Though neither gas is as toxic as hydrogen sulfide or ammonia; both gases pose risks. Carbon dioxide replaces oxygen in the air and it can suffocate people and animals. Methane is flammable and explosive in confined areas and since it is lighter than air, it rises and collects along roof lines. Manure management plans that include powerful ventilation systems can mitigate many potential hazards.
In addition to dangerous gases, manure gives off debris. “Another hazard is caused by particulate dust and others that are carried in the air,” he added. The particulate dust can include airborne organic particles including bacteria, fungal spores and endotoxins.
Minimizing manure hazards
When raising livestock it’s impossible to eliminate manure. However, with sound management practices it is possible to lessen the opportunity for hazards to occur.
“Implement lagoons/ponds to deposit manure and prevent it from going downwards,” Cabrera said. A storage pit prevents manure from leeching. Because lagoons or ponds are deep they can pose drowning hazards. Install a fence around the perimeter or cover the pit to lessen the chance of drowning.
“It’s better if these facilities are covered,” he said. A covered facility lessens the chances dust and particles are released into the air. If a lagoon is covered, it must be well-ventilated, especially during agitation and pumping to avoid exposing people or animals to toxic gases. When the manure is agitated or pumped neither humans nor animals should not be in any adjacent buildings close enough to be affected.
In addition to safe handling techniques, livestock management practices can also contribute to minimizing manure hazards. “Clean up housing facilities and milking parlor frequently and move manure to the storage facility,” he said. Maintaining clean quarters limits the amount of dust, pathogens and odors that are naturally present in manure.
A focus on efficiency can also mitigate manure hazards. Implement processes that can improve productivity and production. “Any management that increases the production reduces the amount of manure being produced per unit of milk produced and therefore is more environmentally friendly,” he said.
“Composting or bio-digesting the manure together with other organic materials is an option,” he said. “Bio-digesting has the additional advantage to produce energy, which could valuable.” Treating manure, either in a digester or by composting, removes the microorganisms that are potentially harmful to humans. “If you prefer to use the manure in a bio digester or to produce compost or humus, all or most of the microorganisms that could be harmful to people and animals disappear after these processes,” he noted.
At a minimum, placement and proper management of composting piles is important for limiting the potential for runoff. Compost piles should be placed away from surface or groundwater sources to limit contamination of water sources. Individual states may have specific composting guidelines in place.
Best of all, after biodigestion or composting, nitrogen and phosphorus are still present making the “treated” manure a nutrient-full option for fertilizer on crops. Manure nutrients help build and maintain soil fertility. Manure can also increase the soil’s water-holding capacity, lessen wind and water erosion, improve aeration and promote beneficial organisms.
Read more: Manure Management: From Compost to Energy
With an increasing focus on environmental conservation, manure handling practices are often required to follow specific regulations. “CAFOs, operations that have more than 700 livestock units (about 700 cows) are required to keep and provide a nutrient balance of the farm,” Cabrera said. A nutrient balance is a record of how much nutrient comes in and how much leaves and therefore how much potential remains or is lost on a farm.
“Organic operations that are certified are also required to keep a nutrient balance record sheet and all documentation needed,” he added. “Dairy farmers are in general committed to environmental stewardship and many of them will do best management practices to reduce or improve environmental impacts voluntarily.”
Because regulations can vary, check with your state’s department of agriculture, the local cooperative extension office and or the United States Department of Agriculture’s Natural Resources Conservation Service (NRCS) for specific guidelines.
Read more: Manure Application Regulations Cumbersome