Introduction

Many farm families throughout the southeastern and Delmarva regions of the United States rely on poultry production as their primary source of income. This has worked well for years but that is changing; due in part to urban encroachment, environmental concerns, increasing regulations, and legal ramifications impacting how producers manage poultry litter. What are some issues associated with litter and what opportunities exist to best deal with this byproduct?

Major Issues

Until recently, most producers spread litter on fields and pastureland. Many producers also have beef cattle as a supplemental income source, taking advantage of litter's fertilizer value. This practice has proven beneficial for decades but after years of spreading litter on fields, soil nutrient is no longer balanced on many fields. Crops need nitrogen (N) present in litter but many soils no longer require phosphorus (P; also present in litter). Fertilizer applications once based on N needs of crops are now based on soil P levels, preventing or limiting amount of litter some producers may apply.

* "Use common sense and good neighbour practices whenever it is time to spread litter"

Producers able to apply litter based on nutrient management plans and soil tests are also at risk. Concerns over N loss from ammonia volatilization, P in surface run-off, odours, dust and complaints from neighbours take their toll on producers and their families. Poultry and livestock operations in both Europe and the United States are the largest sources of ammonia emissions, accounting for an estimated 70-90 per cent of total emissions (Mukhtar et al., 2006).

Ammonia volatilization decreases litter N content and represents a significant loss of fertilizer value (Tabler, 2006a). In the past, ammonia was considered a nuisance odour emitted from poultry houses. However, due to its large output from poultry farms and its rapid reaction with strong atmospheric acids (nitric and sulphuric) to produce ammonium salts (PM2.5), ammonia emissions are now being heavily investigated (Baek et al., 2004). In many parts of the United States, the fraction of PM2.5 associated with ammonia emissions is as much as 50 per cent of total fine particle mass (Strader & Davidson, 2006). It is likely regulations addressing ammonia emissions are in agriculture's near future. Best management practices (BMPs) should be in place and utilized in several different areas to help reduce ammonia emissions. Major sources of ammonia emissions from poultry production include the poultry house itself, litter storage facilities and fields where litter is applied, each source requiring its own specific BMPs.

Dust and odour associated with litter is another critical issue for producers. Even though dust and odours have always been associated with livestock production, management of dust and odours becomes more important as operations become larger and more concentrated (Ullery et al., 2003). Dust and odours from livestock operations have recently become a highly emotional issue due to the influx of city dwellers to rural, agricultural areas. Producers and newfound neighbours have vastly different ideas about what 'life in the country' means. This has led to an escalating number of complaints to authorities and an increase in the number of local governments considering set-back requirements or other siting regulations for new or expanding agricultural operations.

It is difficult and expensive to study the exact make-up of odours because most are made up of many different gases at extremely low concentrations (Jacobson et al., 2006). Spilled feed, bedding material and the poultry or livestock themselves account for a portion of livestock odours but most poultry and livestock odours result from decomposition of manure (Tabler, 2006b). Odour concentration can be quite variable depending on level of microbial activity in the litter or manure. Microbial activity and growth are dependent on moisture content, pH, temperature, oxygen concentration and other environmental factors such as wind speed, wind pattern and season (Tabler, 2006b).

Dust aggravates the odour situation by acting as a transport mechanism capable of carrying odours long distances on air currents. Excessive dust in poultry houses is also a detriment to house environment and may adversely affect health of birds and workers. Several sources in the poultry house can contribute to dust generation including bedding, manure, feed, dander, feathers and bacteria. Proper management can maintain in-house dust at manageable levels. Unfortunately, spreading litter usually generates significant amounts of dust and, in some cases, complaints, as well. Therefore, use common sense and good neighbour practices whenever it is time to spread litter.

Opportunities

Addressing proper management and disposal of poultry litter offers opportunities for new and innovative thinking. For example, most poultry litter is spread on grassland surface that has raised serious run-off and water quality concerns in many areas. However, incorporation of litter into the soil has proven to be an effective technique for decreasing volatilization and run-off losses in some cropping systems. Pote et al. (2003) developed a knifing technique that minimized disturbance of the soil structure, forage crop and thatch while incorporating poultry litter below the surface of established perennial grassland. Nutrient concentrations and mass losses in run-off from incorporated litter were significantly lower (generally 80-95% less) than in run-off from surface-applied litter. By the second year, litter-incorporated soils had greater rain infiltration rates, water-holding capacity and sediment retention, and showed a strong tendency for increased forage yield (Pote et al., 2003). In follow-up work, Pote et al. (2006) developed a mechanical incorporator that applied poultry litter under the pasture surface, decreasing nutrient losses in run-off about 90% and tended to increase forage yield.

Current research is focused on testing a multi-shank incorporator that can rapidly apply several tons of litter beneath a grassland setting before reloading (Pote, 2008), similar to surface application methods. Such innovative thinking and product development could potentially offer multiple benefits to producers and integrators. Not only would incorporation greatly reduce surface run-off and the threat to water quality but ammonia volatilization, dust, odour and complaints would also likely be reduced compared to surface application.

Vegetative environmental buffers or windbreaks are an old technology that holds new promise for tunnel-ventilated, totally enclosed poultry houses. Windbreaks are able to buffer dust, odours and noise emissions from poultry houses while adding to property values and aesthetics, as well as foster improved neighbour relations (Tyndall, 2008). As the windbreak matures, it also adds a visual screening effect to agricultural operations. The Applied Broiler Research Farm recently planted a four-row windbreak in front of four tunnel fans at one broiler house. The windbreak contains two rows of a deciduous species (closest to the fans) and two rows of evergreens. Deciduous trees planted as the first rows opposite fans tend to withstand the high-particulate loads best because particulate matter accumulating on leaves during summer when tunnel fans are in use will drop off with the leaves in the fall and new leaves will grow the following spring. Mixing of species is recommended for two reasons:

1. increased species diversity reduces the risks of whole scale pest/pathogen loss
2. some species, e.g. poplars, featuring very rapid growth may have relatively short healthy life span (Tyndall, 2008).

To ensure livability, the minimum distance of the vegetative buffer from fans is to be 10 times the fan diameter (Malone et al., 2006). To encourage initial establishment and growth, effective irrigation and weed control programs are essential.

Biofilters

Biofilters are another odour-control device recently adapted for livestock and poultry operations that are both economical and effective. The technology is popular in northern Europe and is attracting increased attention in the United States. Biofiltration can reduce odour and hydrogen sulphide emissions by as much as 95 per cent and ammonia by 65 per cent (Nicolai & Schmidt, 2005; Nicolai et al., 2006; Sun et al., 2000). Typically, a biofilter is a layer of compost and wood chips that support a microbial population, or simply a bed of organic material 10 to 18 inches deep (Schmidt et al., 2004). Microbes associated with the organic material convert odorous gases to carbon dioxide and water as air passes through the biofilter. Schmidt et al. (2004) illustrated elements of an open-bed biofilter (Figure 1) which include:

• A mechanically ventilated space with biodegradable gaseous emissions
• An air handling system to move the odorous exhaust air from the building or manure storage through the biofilter
• An air plenum to distribute the exhaust evenly beneath the biofilter media.
• A structure to support the media above the air plenum.
• Porous biofilter media that serves as a surface for microorganisms to live on, a source of some nutrients, and a structure where moisture can be applied, retained, and available to the microorganisms

Biofilters do require maintenance in four areas - assessing pressure drop across the media, weed control, rodent control and moisture control (Nicolai & Schmidt, 2005). Moisture control is critical for the biofilter to properly reduce odour. Media selection is also important with critical properties including 1) porosity, 2) moisture holding capacity, 3) nutrient content, and 4) slow decomposition (Schmidt et al., 2004). Exhaust fans will also need to be checked (and possibly replaced) to be sure there is enough fan power to both ventilate the building and push the exhausted air through the biofilter.

Summary

Many farm families rely on poultry production as their primary income source. The litter byproduct from this production is a major concern for producers and the industry today. It will require new and progressive thinking and development of new tools to solve the problem.

Currently, this type of work is ongoing across the country. From innovative equipment design to vegetative buffers to biofilters and more, research continues to focus on efforts that help farmers farm while keeping neighbours happy and protecting the environment. However, producers should be proactive and involved when air emission controls are discussed to prevent misguided regulations that demand unrealistic expectations from the agricultural industry.

References

Baek, B.H., B.P. Aneja & Q. Tong. 2004. Chemical coupling between ammonia, acid gases, and fine particles. Environ. Pollution. 129:89-98.
Jacobson, L.D., J.A. Kosiel, S.J. Hoft, A.J. Heber & D.B. Parker. 2006. Odor emissions and chemical analysis of odorous compounds from animal buildings. Pp 4-14. Proc. Workshop on Agricultural Air Quality: State of the Science. Potomac, MD. June 5-8.
Malone, G.W., G. VanWicklen, S. Collier & D. Hansen. 2006. Efficacy of vegetative environmental buffers to capture emissions from tunnel ventilated poultry houses. Pp 875-878. Proc. Workshop on Agricultural Air Quality: State of the Science. Potomac, MD. June 5-8.
Mukhtar, S., A. Mutlu, S. Capareda, R. Lacey, B. Shaw & C. Parnell. 2006. Seasonal and spatial variations of ammonia emissions from an open-lot dairy operation. Pp 943-946. Proc. Workshop on Agricultural Air Quality: State of the Science. Potomac, MD. June 5-8.
Nicolai, R.E., C.J. Clanton, K.A.Janni & G.L. Malzer. 2006. Ammonia removal during biofiltration as affected by inlet air temperature and media moisture content. Trans. ASABE. 49(4):1125-1138.
Nicolai, R. & D. Schmidt. 2005. Biofilters. South Dakota State University Fact Sheet. FS 925-C. South Dakota State University. Brookings, SD.
Pote, D.H., W.L. Kingery, G.E. Akin, F.X. Han, P.A. Moore, Jr. & K. Buddington. 2003. Water-quality effects of incorporating poultry litter into perennial grassland soils. J. Environ. Qual. 32:2392-2398.
Pote, D.H., T.R. Way, W.L. Kingery, G.E. Akin, K.R. Sistani, F.X. Han, and P.A. Moore, Jr. 2006. Incorporating poultry litter into perennial grassland to improve water quality. Proc. Arkansas Water Research Center Conf. Publ. date: April 18, 2006. Abstr.
Pote, D.H. 2008. Personal communication.
Schmidt, D., K. Janni & R. Nicolai. 2004. Biofilter design information. Biosystems and Agricultural Engineering Update. University of Minnesota Extension Service. Publ. No. BAEU-18.
Strader, R. & C. Davidson. 2006. Ammonia emissions from agriculture and other sources. Proc. Workshop on Agricultural Air Quality: State of the Science. Potomac, MD. June 5-8.
Sun, Y., C.J. Clanton, K.A. Janni & G. Malzer. 2000. Sulfur and nitrogen balances in biofilters for odorous gas emission control. Trans. ASABE. 43(6): 1861-1875.
Tabler, G.T. 2006a. Ammonia emissions attracting significant attention. Avian Advice 8(2):9-11.
Tabler, G.T. 2006b. Odor – An emerging concern for producers. Avian Advice 8(1):1-3.
Tyndall, J. 2008. The use of vegetative environmental buffers for livestock and poultry odor management. Proc. Mitigating Air Emissions from Animal Feeding Operations Conference. Des Moines, IA. May 19-21. Iowa State University.
Ullery, C., S. Pohl, A. Garcia, H. Stein, K. Tjardes, & C. Schmit. 2003. Odor management information for livestock operations. South Dakota State University Extension Publ. No. ESS803-A. South Dakota State University. Brookings, SD.

September 2008