Nutrient Utilization Calls for Precision

As it pertains to manure handling and management, pork producers and their advisors must be well equipped with the scientific principles of biology, chemistry and physics to provide a healthy environment inside the production complex as well as the surrounding, outside environs. 

October 15, 2012

9 Min Read
Nutrient Utilization Calls for Precision


Modern pork production is extensively rooted in the various fields of business and science. As it pertains to manure handling and management, pork producers and their advisors must be well equipped with the scientific principles of biology, chemistry and physics to provide a healthy environment inside the production complex as well as the surrounding, outside environs.

All environmental rules are presumed to have underlying sound science as their basis. However, the many environmental regulations imposed on the swine industry are arguably more exacting than those required of other livestock production facilities. Those who have pushed these additional impositions typically claim to be targeting corporate production facilities, while the collateral damage of their initiatives has proven to be especially burdensome to family-sized production units.

While those in positions of regulatory authority and decision-making are generally fair-minded and well-schooled in the science and practical aspects of manure management and its interactions with soil and water in the environment, there are some who are not.


Water Quality

The Clean Water Act of 1972 (CWA) is the most universally recognized and relied-upon basis for regulations pertaining to environmental protection. The best-known provisions of the CWA are the requirements for all confined animal feeding operations (CAFOs) with over 1,000 animal units (2,500 pigs weighing 55 lb. or more) that discharge pollutants to the waters of the United States to have a National Pollutant Discharge Elimination System (NPDES) permit authorizing such discharge.

The CWA is the enabling legislation that also brought together all federal environmental functions at the time to form the Environmental Protection Agency (EPA). Other regulations have since come into being to deal with air pollution, etc., which have expanded the responsibilities of the agency.

The provisions of the CWA are often relied upon by state and other public jurisdictions as the basis for state and local rules and regulations protecting water quality. The CWA requirement for NPDES discharge permits has been widely assumed to apply to every swine production CAFO. Virtually all CAFOs have an NPDES permit issued directly by the EPA or a state designated agency. What the environmental bureaucracy and most of the industry missed, up until court decisions rendered in the last decade, is that having a “discharge” to waters of the United States is critical to the requirement for a discharge permit, regardless of CAFO size or location.

Due to the high level of environmental control and protection over the animal environment, as well as the design and management of the most prevalent manure storage/treatment facilities, there is little chance of a discharge occurring from typical swine facilities today. Therefore, virtually all typical swine production facilities are technically exempt from the requirement to have an NPDES permit.

Although CAFO facilities utilizing open lots subject to storm water runoff are virtually non-existent in U.S. pork production, they do have potential to discharge and, thus, require an NPDES permit. As a practical matter, however, many regulatory jurisdictions have capped the CWA-NPDES requirements with local regulations that still require compliance. Producers must know and understand what is really required in the jurisdiction where they are located vs. what is anecdotally presumed to apply.


Capitalize on Technology

The swine industry has been very dynamic in adopting and applying modern technology to manure management systems. The best options are typically site-specific.

In siting new facilities, it is more critical than ever to thoroughly consider nearby odor receptors and levels associated with the proposed facilities. Most jurisdictions have siting separation distance, odor dispersion/modeling or even air pollution rules that must be adhered to.

Properly sited, well-designed and well-managed manure storage/treatment lagoons are still one of the most economical and environmentally secure technologies available, although some jurisdictions have imposed restrictions that make them more difficult to get permitted. A few jurisdictions simply do not allow earthen or even synthetic-lined lagoons, regardless of their efficacy at limiting odors and preventing water pollution.

As energy costs rise and incentives for renewable energy become more progressive, the opportunities to utilize technologies such as the production of biogas from the anaerobic digestion of manure will become more practical, while also significantly reducing odor potential and air pollutant emissions from stored manure. The digestate remaining after anaerobic digestion is highly stabilized and has much lower odor potential than raw manure, thus alleviating most of the odor and air pollution concerns with open lagoon storage.

Anaerobic digestion can be utilized under a range of different formats, depending upon site conditions and project goals. These formats range from ambient-temperature, covered lagoons on the low-cost side, to heated and covered lagoons, to complete mixed digesters or fixed media technologies that utilize in-ground or above-ground tanks on the more sophisticated side. Metabolic reaction rates and, thus, digestion time ranges from slow, with covered lagoons, to very rapid with mixed digesters and fixed-media technologies.

Anaerobic digestion provides high levels of manure treatment/stabilization in a controlled environment that dramatically limits the escape of odorous compounds from the process vessel. The treated effluent is generally well stabilized such that odors are largely attenuated.

One of the simplest forms of anaerobic digestion, using the term very loosely in this case, is a covered lagoon that simply utilizes a gas- tight cover. The anaerobic digestion process is naturally occurring under favorable concentrations of manure vs. dilution. While the process is not highly controlled in this configuration, the process results in storage and treatment without significant odor escape.

More sophisticated and highly controlled anaerobic digestion can take the form of more rigorously sized covered lagoons located in moderate climates where the process functions at a relatively high level based solely on ambient temperatures. The next level up the process chart would involve heating and insulating the covered lagoon for consistent, high rate, year-around gas production and utilization.

Finally, fully embellished anaerobic digestion technologies such as mixed-and-heated digesters in above-ground or in-ground storage tanks provide high levels of manure stabilization, high levels of gas production, and attendant high levels of odor control and reduction. More refined and sophisticated digestion technologies include induced bed reactors, sequencing batch reactors, fixed media reactors and membrane filter reactors, among other variants.

Each technology has its own specific parameters, advantages and cost factors. All anaerobic digestion technologies have the potential of significantly reducing odor and air pollution potential while significantly reducing the carbon footprint of the swine


Manure Handling, Storage

The capstone preference for any manure management technology is for the immediate removal of manure and urine from a facility vs. storing it within.

Flushing — When I first started trouble-shooting and designing swine production units in the early 1970s, the focus was on improving the air quality for pigs and workers in the building by frequently and efficiently removing manure and urine from the animal space. Generically referred to as flush systems, they simply harnessed the energy of moving water to collect and remove manure from the interior environment.

When well designed, these systems are energy efficient and generally configured to function within the available water supply and utilization regime on the farm. An often misplaced emphasis on water-use efficiency, even when most of the water was recycled, moved the industry away from a wide reliance on “active hydraulic flushing” to gravity drain systems (passive flushing) or pull-plug systems. These systems reverted to storing manure in the building for relatively short periods of time, ranging from one week to a month or more vs. deep-pit, long-term storage up to a year. Well-designed and managed hydraulic flushing systems are still one of the most efficient systems for assuring and protecting high air quality and sanitation in the pig/people environment.

Manure scrapers — Also in the ’70s, the industry explored the use of pit scrapers as another option for frequent manure and urine removal. Mechanical and maintenance problems, along with the persistent microbial inoculum on the pit floor that hastens manure and urine transformation to odorous compounds, took these types of systems out of favor.

In recent years, however, alternative approaches to segregate manure from urine have shown great promise for preserving and protecting indoor air quality in several research settings. One of the most notable is the Sekine scraper system from Japan, which was installed at Michigan State University in the 1990s. The system provides very low odor discharge from the segregated manure and urine streams. However, in spite of their generally excellent air quality performance, segregating systems have not made the leap from research and demonstration facilities to general production facilities in the United States.


Manure Nutrient Utilization

Every production facility produces significant manure nutrient resources for utilization on local crops or for export to other uses. When the production facility is not integrated with owned cropping resources capable of utilizing manure nutrients, there are significant advantages to developing systems to export the nutrients.

Under EPA rules, exported nutrients are regulated just like any other agricultural fertilizer vs. the extensive regulatory planning, application, annual updates, soil and manure testing and recordkeeping required when the production facility is responsible for land utilization. Manure treatment and storage systems that accomplish nutrient segregation assist with economically and environmentally sound export of nutrients.

Land application efficiency favors irrigation where manure stabilization and treatment and odor reduction processes or lack of nearby odor receptors allow. More advanced irrigation technologies, such as subsurface drip irrigation, are gaining interest due to their ability to essentially eliminate all odor emanation, as well as the visual objections. This technology also provides very comprehensive control over nutrient application rates, timing and efficiency.

Alternative practices, such as immediate tillage or knifing manure or wastewater into the soil, may still be required where manure or wastewater odors are objectionable.


Technical Services

U.S. pork producers have long enjoyed free technical services provided by publically funded and commercial sales support. While this paradigm has served the industry well for decades, it has perhaps stymied the widespread utilization of professional technical service providers. Even so, a few dedicated professionals with high-level expertise and vision have survived to provide high-quality designs and services.

While some of the larger swine production companies now include manure and environmental management specialists within their corporate structure, others in the industry can benefit from more expansive use of highly competent, independent technical advisors and service providers. These design and technical professionals can help position new or renovated facilities at the leading edge of technology and help walk them through the many regulatory and technical pitfalls they may

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