In the past several decades, manure management practices associated with the pork industry have progressed, resulting in improved production efficiency and a healthier environment for the animals.
In some cases, changes were mandated by local, state and/or federal requirements. These changes involved manure handling, storage and land application practices that were based on sound science and recycling of targeted manure nutrients to enhance crop yields.
Most manure management practices continue to involve land application of manure slurry and nutrients relatively close to animal production sites.
However, this model is likely to present a challenge for long-term generational sustainability in many areas where pork is produced under current confined-animal-feeding conditions.
To ensure that pork production models are able to meet the demand for protein and remain generationally sustainable, the future of manure management will require technology applications that provide alternatives to current manure management practices.
As pork production has expanded in the late 20th and early 21st centuries, significant efforts and resources have been expended by pork producers and public and private sectors to develop and implement new manure management technology. These efforts have produced options for producers that vary in complexity and cost as well as objectively determined success.
Some of the more innovative technology options have been adopted by some pork producers. An Oct. 15, 2012 National Hog Farmer article (See: “Nutrient Utilization Calls for Precision”) by John A. George, Agricultural Engineering Associates of Uniontown, KS, correctly noted that the pork industry has been dynamic in applying technology systems based on site-specific needs. The adoption of technology options by producers in many cases is also driven by state-specific economic incentives.
For example, some pork-producing states offer programs that encourage production of renewable energy that can be generated from anaerobic digester (AD) biogas systems. These systems have been extensively researched and developed worldwide in part to address increased energy costs. This has resulted in a variety of AD systems available to producers from simple on-farm covered lagoon systems to highly automated, sophisticated, centralized systems serving multiple farming operations.
However, the number of AD systems in pork operations remains low largely due to economic cost.
Many technology applications, including AD systems, have been investigated and implemented by producers to address issues associated with odorous emissions. Air scrubbers, biofilters and more simple, less technology-driven approaches such as pit or lagoon additives have been studied or utilized on the farm.
Biofiltration has been shown to be very effective in reducing air emissions from pork production facilities. As with AD technology, a variety of approaches have been studied, including simple biomass containment structures composed of straw or wood chips located at prescribed distances from ventilation fan exhaust to enclosed systems directly interconnected to the barn ventilation system. The latter systems have been shown to be the most effective. But issues associated with operational feasibility, rodent control, ventilation concerns and production costs have impeded implementation of these technologies.
Collaborative research at North Carolina State University and West Virginia University is exploring ways for coupling a biofilter with a heat exchanger that would allow heat recovery to temper the fresh inlet air going back into the barn during heating seasons.
Research at Iowa State University has shown promising results for an “Impact-Based Odor Control” (IBOC) technology, which is essentially a biofilter-linked system that monitors emission and weather patterns and engages the biofilter only when needed to reduce impact on neighbors. This enables the system to minimize energy use and be more affordable while maximizing odor mitigation.
Collectively, both of these systems represent promising approaches and concepts to future affordable technology options for addressing barn emissions.
A related approach to biofiltration includes landscaping around the barn with vegetative environmental buffers (VEB). Vegetative environmental buffer systems composed of a combination of select trees, shrubs and grasses have been shown to reduce downwind odorous emissions from tunnel-ventilated swine production barns. A mature VEB will essentially increase dilution of odor emissions (forcing the plume to mix vertically), as well as serve as a biomass sink to capture exhausted odorous dust particulates and animal dander in the vegetation. A further benefit is the visual buffer provided by a mature VEB.
Pictured are the above-ground tank components for an environmentally superior treatment system for a 13,000-head, feeder-to-finish and 2,400-head sow farm.
Pit or lagoon additives (biological, chemical or physical absorbents) continue to be widely marketed to pork producers. University research and Extension personnel receive frequent inquiries from producers as to efficacy of these products, and controlled laboratory and field research have produced mixed results.
The bottom line is that producers should be cautious when considering investment in these products and make a careful assessment regarding rate of application and targeted results. Some additives may clearly impact solids concentrations in pits or lagoons and/or reduce certain odorants and gases that make up the complex mix of compounds characteristic of odorous emissions.
For example, these additives may significantly reduce ammonia and/or hydrogen sulfide, which would be beneficial to the animal and worker environment. However, odorous emissions as perceived by nearby neighbors may not be significantly impacted.
A swine manure management technology development and verification process initiated in 2000 in North Carolina through a state government-industry-university agreement yielded a tremendous amount of objective information regarding environmental performance and costs of several systems. The initiative was structured to determine whether systems met environmental performance, operational feasibility and economic standards to qualify as environmentally superior technologies (EST).
Environmental performance targeted nutrient impacts to surface and groundwater, emissions of ammonia and odor, disease-transmitting vectors and airborne pathogens, and heavy metal (copper and zinc) impacts to soil and groundwater.
Economic feasibility was based on a cost-return metric including the projected 10-year annualized cost (capital, operational and maintenance) of the technology system expressed as a cost per 1,000 lb. of steady state live-weight (SSLW) for a categorized farm system. (Table 1).
Projected revenues, including income from waste treatment byproduct utilization (i.e., marketable fertilizer products from processed solids or renewable energy from AD, gasifier or combustion systems), as well as tax incentives, carbon or green energy credits, etc., were considered.
The process yielded numerous technologies, including solids separation systems, energy recovery systems, biological nitrification and de-nitrification systems, belt manure removal systems, composting systems, wetland systems and others. All systems were critically evaluated, most on commercial pork production farms, for environmental performance, operational feasibility and costs over a period of time to include at least one climatic “cool” season of production and one climatic “warm” season of production.
The solids separation rotary press unit for an environmentally superior treatment system for a 13,000 head, feeder-to-finish farm and two, 1,200-head sow farms.
Results showed that environmental benefits were achieved for many of the target parameters by many of the systems evaluated. Five systems met the environmental performance standards for all five targeted parameters1:
1. A solids separation–nitrification-denitrification — soluble phosphorus removal system (Super Soils, renamed Terra Blue in 2010)
2. An enclosed, high-temperature, high-solids anaerobic digester system (ORBIT)
3. A gasification system for processing belt-delivered solids (Gasifier Recycle)
4. A centralized, automated composting system for processing solids (Super Soils Compost System, renamed Terra Blue in 2010).
5. A fluidized bed combustion system for processing swine manure solids blended with spent turkey litter (BEST).
The economic cost and return results for each of these candidate EST systems is shown in Table 1. For comparison, the cost of a typical lagoon sprayfield system in North Carolina is also shown in Table 1.
A complete EST system must be able to treat both the liquid and solids components of swine manure. Thus, for purposes of meeting the North Carolina requirements for this initiative, the solids separation–nitrification-denitrification — soluble phosphorus removal system would need to be coupled to any of the four approved EST systems for treating solids. As such, it was determined that a complete EST system did not meet economic feasibility criteria. These determinations were made in 2006. The complete report is available at http://www.cals.ncsu.edu/waste_mgt/smithfield_projects/phase3report06/phase3report.htm.
Since 2006, several of the technology supplier groups have continued to be involved in livestock and agricultural waste treatment as well as other waste feedstock treatment applications.
Subsequent efforts by some of the technology suppliers and university researchers involved in the original EST initiative have been directed specifically at pork production. The objective is to improve on-farm treatment processes to reduce the costs of their respective treatment systems, while maintaining environmental performance.
One initiative involved application of value engineering changes to the above-referenced solids separation–nitrification-denitrification — soluble phosphorus removal system. Environmental performance of the modified systems has been evaluated on two commercial farm sites in North Carolina. One site was a 6,000-head finishing operation, the other is two, 1,200-sow farms combined with a 13,000-head finishing operation.
An overview of the environmental results and associated 10-year annualized cost for these modified generation 2 and 3 systems is shown in Table 2.
These results show that organized efforts to reduce costs of verified EST are achievable. There is no doubt that affordability will be essential for widespread adoption of innovative technology in the future.
In addition to efforts directed to reduce the cost of verified EST, another approach has been to critically examine some of the more affordable candidate EST technologies that did not meet all of the environmental performance standards — technologies that were considered “on the bubble” by meeting three or four of the mandated five environmental criteria and just missing on the one or two criteria that did not meet the bar.
One such example was the ambient temperature anaerobic digester and greenhouse for swine waste treatment and bioresource recovery system (Barham Farm). The 10-year annualized cost for this system was approximately $90 per 1,000 lb. SSLW/year. The system met four of the environmental performance standards but did not meet the ammonia emission standard. To keep energy cost low, a simple trickling filter infrastructure was utilized for the first generation of this system to treat the ammonia in solution from the in-ground ambient digester effluent.
While the trickling filter system was effective at nitrifying the ammonia, it did not sufficiently nitrify in adequate concentrations to sufficiently reduce ammonia emissions to the desired standard. Subsequent redesign of the trickling filter system by researchers at North Carolina State University in collaboration with the farm owner may be sufficient in reducing the ammonia to required levels.
Collectively, these approaches — applications to reduce cost of proven EST systems and modification of more affordable on the bubble candidate EST — should yield promising technology options for pork producers in the future.
As we look to the future and explore strategies to ensure that U.S. pork producers are afforded technology options that will enable them to be globally competitive and meet the environmental challenges associated with meeting pork demand, it is essential that we consider options that will reward implementation of innovative manure management technology. It is recognized that, especially in the United States, energy production from renewable resources such as manure remains a more expensive option compared to energy produced from coal, natural gas and nuclear energy, resulting in few incentive programs for broad adoption of AD systems in animal production.
However, as we have learned more about the benefits to animals, farm workers and neighbors related to improved animal waste treatment practices, the need for policy that rewards U.S. producers for implementing such technology is apparent.
Policy or regulations that simply result in the relocation of pork production from one part of the globe to another, without the improved manure management systems, is ill-informed and will not benefit society in the short and especially long term. Institutional incentives and the development of markets that will reward farmers for utilizing technology systems that are documented to yield environmental benefits is a direction of progress to ensure that U.S. pork producers are part of the supply chain to meet global pork demand in the future.
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