Air Quality and Livestock Farming

Thomas Banhazi, Andres Aland, Jörg Hartung, Thomas Banhazi, Andres Aland, Jörg Hartung

• Editore: CRC Press
• Anno: 2018
• ISBN:
  9781317573401
• Edizione: 1
• Argomento: Medizin
• Categoria: Veterinärmedizin

Air quality has a direct influence on health, welfare and production performance of livestock as the high concentrations of noxious gases, dust and airborne microorganisms are likely to reduce production efficiency and the general welfare of farm animals. Long term exposure to particulates in livestock buildings might also affect the respiratory health of farm workers. Dust in animal buildings contains many biologically active substances such as bacteria, fungi, endotoxins and residues of antibiotics (as a result of veterinary treatments) that are suspected to be hazardous to human health. Furthermore, air pollutants emitted from livestock buildings can reduce air, water and soil quality and can potentially undermine the health of nearby residents. Airborne emissions include ammonia, methane, nitrous oxide, particulates like dust and microorganisms. In addition, other potentially harmful substances such as heavy metals, antibiotic residues and components of disinfectants might be also emitted from livestock building that are potentially damaging to ecosystems.
In this book, key aspects of agricultural air quality, such as monitoring, managing and reducing airborne pollutants in and around livestock facilities are reviewed.

Features:

• addressing the raising awareness of the importance of optimal health and welfare for lifestock species
• with contributions from international specialists and researchers
• providing up-to-date information for professionals involved in modern animal producti

This book will be useful for farming professionals, academics, students, policy makers, business leaders, regulatory bodies and agricultural consultants.

Section V

Reduction methods Controlling internal concentrations and emissions from the animal buildings

Chapter 16

Controlling the internal concentrations of gases and odor within and emissions from animal buildings

Jens Seedorf

16.1 A general view on airborne pollutants – an introduction

The supply of appropriate ventilation and fresh air is a vital ingredient in managing healthy farm animals and reducing the Occupational Health and Safety (OH&S) risks associated with farm work. Consequently, any deterioration of the quality of air might affect the well-being of exposed individuals. Therefore, gaseous and particulate airborne pollutants play an important role in livestock husbandry (Eduard et al., 2009; European Food Safety Authority, 2012; Hallam et al., 2012; Hooser et al., 2000; Miles et al., 2006; Omland, 2002; Pejsak et al., 2008; Szczyrek et al., 2011; Urbain et al., 1997; Von Essen et al., 2010). The combined presence of airborne pollutants in livestock buildings might result in greater harm than their individual effects would have (Donham et al., 2002; Hamilton et al., 1999; Murphy et al., 2012; Urbain et al., 1996). Admittedly, this combined impact cannot be established in each individual case (e.g., Done et al., 2005) especially when management and genetic factors interfere or even protective health effects of the farming environment occur (e.g., Braun-Fahrländer, 2013; Peters et al., 2006; Radon, 2006; von Mutius and Radon, 2008; von Mutius et al., 2000).

Once released into the atmosphere, the emitted airborne pollutants might 1) cause acidification and eutrophication of soil and surface water (e.g., Stevens et al., 2006), 2) alter the abundance and diversity of terrestrial plant (e.g., Payne et al., 2013; Southon et al., 2013), 3) change the climate (e.g., IPCC, 2013), 4) transmit microorganisms and diseases (e.g., Dijkstra et al., 2012; Gloster et al., 2003; Seedorf et al., 2005), or spread 5) dust-borne antibiotics (e.g., Hamscher et al., 2003) and 6) antibiotic-resistant microorganisms of public health concern (e.g., Alvarado et al., 2012; Friese et al., 2013; Gibbs et al., 2006; Schulz et al., 2012; Zahn et al., 2001) into the surrounding space, depending on the prevailing meteorological and topographical conditions. Emission inventories are useful tools with which to overview the potential geographic distribution of airborne pollutants (e.g., Pattey and Qiu, 2012; Seedorf, 2004a). The results derived from investigations related to community health issues are complex but more useful in assessing the impacts of emission. There are reports available on environmental health effects (e.g., McElroy, 2010; Radon et al., 2007; Schulze et al., 2006, 2011; Wing and Wolf, 2000), but the transmission-based impacts of pollutant release are not fully understood due to inconsistent results from different studies, as concluded by O’Connor and co-authors (2010).

Thus, it is obvious that a review of airborne pollutant control and reduction is beneficial and might initiate the implementation of precautionary measures on farms. It is therefore not surprising that previous studies on airborne pollutants have already highlighted various measures aimed at generally improving the air quality in livestock buildings (e.g., Basinas et al., 2013, 2014). However, any reduction measure implemented within livestock buildings will generally decrease the burden on the environment as well. This aspect is already regulated in the EU-Directive 2010/75/EU, which lays the foundation for the reference documents for best available techniques (Best Available Technique Reference Documents, BREF) as a basis for the legal permission of the construction and operation of livestock buildings with specific herd sizes in Europe (European Commission, 2003; European IPPC Bureau, 2013; Grimm et al., 2013). Nonetheless, end-of-pipe technologies, such as biological exhaust air purification systems, are a further option to achieve environmental protection standards with respect to ammonia, odor and dust (e.g., European IPPC Bureau, 2013; Iranpour et al., 2005; Melse, 2009; Seedorf, 2004b), but, on the other hand, the biosecurity of such devices was questioned (Seedorf, 2013).

There is a relative diversity of management tools and technical applications to mitigate the extent of releasable pollutants, which can be exemplarily perceived for NH₃ (Botermans et al., 2010; UNECE, 2001): a classic agriculture-related pollutant over the past decades. The aim of this chapter is therefore to build a general understanding of the sources and the basic mechanisms of airborne pollutant formation, which is additionally underlined by the basic characteristics of a selection of gases and odor in livestock operations. From this point of view, a number of control and reduction measures can be derived, as shown in the subsequent literature review.

16.2 A brief description of relevant gases and odor

Ammonia (NH₃), with its colorless, sharp and intensely irritating properties, is the most dominant and harmful gas in livestock buildings, and it is generated by the degradation of urea and uric acid, which are excreted by mammals and poultry, respectively. The chemical reaction responsible for this airborne pollutant is triggered by the enzymes, urease and uricase, which are released by feces- and environment-associated microorganisms that are partly related to the family Enterobacteriaceae, such as Proteus spp. or Klebsiella spp. (Groot Koerkamp et al., 1998; Mobley and Hausinger, 1989). The magnitude of NH₃ volatilization mainly depends on the temperature and the pH value, which determine the ammonium–NH₃ equilibrium (pK_a = 9.25). Higher temperatures and increasing pH values favor the release of NH₃, which is lighter than air (ATSDR, 2004). In addition to urea and uric acid, other nitrogen (N)-containing agents, such as proteins, can also be biochemically degraded, which also results in the production of NH₃. Furthermore, NH₃ acts as a precursor in the formation of secondary particulate matter (PM) in the environment (Hertel et al., 2011) and is therefore a cofactor in the generation of an anthropogenic albedo caused by aerosol and radiation interactions such as scattering and radiation absorption (IPCC, 2013). Interacting forces between NH₃ and aerosols cause a gas-particle association (Reynolds et al., 1998; Takai et al., 2002).

Hydrogen sulfide (H₂S) is a heavier-than-air, colorless gas with a characteristic odor of rotten eggs, which can be perceived at very low concentrations. Documented odor threshold values range between 0.0005–0.010 ppm and 0.02–0.13 ppm. The gas is mainly formed by the decomposition of sulfur (S)-containing organic compounds in manure under anaerobic conditions (ATSDR, 2006; Costigan, 2003). Under normal operations, H₂S is a trace gas within livestock buildings, because H₂S concentrations generally reach the ppb level rather than ppm levels (e.g., Kim et al., 2008a; Lim et al., 2003; Ni et al., 2002; Zhao et al., 2007), although Jacobsen et al. (1997) reported concentrations up to 118 ppm observed directly above animal manure storages; in addition, it can be assumed that H₂S concentrations in the air can vary widely during manure management activities. Conclusively, relatively high and, therefore, unhealthy concentrations can be reached when manure is agitated during dunging out operations along with insufficient air exchange close to the gas source (ATSDR, 2006; Chénard et al., 2003; Hooser et al., 2000; Swestka, 2010). In contrast to NH₃, H₂S exhibits a relatively weak acidic character. In this context, Swestka (2010) cited Snoeyink and Jenkins (1980), who stated that in solutions with a pH of 7, H₂S and HS are present in equal concentrations (pK_a = 7). As the pH decreases, more hydrogen ions are available, and thus, more H₂S is present. Below a pH of 5, all sulfides in solution are H₂S.

Carbon dioxide (CO₂), which has a remarkably higher physical density than air, is mainly an end product of the mammal’s metabolism, and it is exhaled via the respiratory tract into the ambient air, but this colorless and odorless gas is additionally formed by microbial activities in manure. Urea (CO[NH₂]₂) is converted into ammonium (NH₄⁺), a hydroxyl ion (OH^–), and bicarbonate (HCO₃^–) in the presence of water and urease enzymes. The formed bicarbonate evolves into CO₂ and water (Snyder et al., 2009). The enzymatic degradation of uric acid also produces CO₂. In addition to biological sources, gas-fired heaters can play a significant role in CO₂ release (e.g., CH₄ + 2 O₂ → CO₂ + 2 H₂O). Excessive exposure to CO₂ impairs animal performance due to a relatively higher uptake of the gas into the blood in comparison to oxygen (Reece and Lott, 1980). This is particularly valid for fast-growing animals, such as broilers, where oxygen would be displaced by CO₂, according to Dalton’s law of partial pressures. The resulting imbalance between the oxygen supply and the required oxygen can even facilitate the generation of metabolic diseases, such as ascites (Beker et al., 2003).

In contrast to CO₂, with high toxicological tolerance in mammals but general importance for climate change, carbon monoxide (CO) is an undesirable by-product of the incomplete combustion processes of hydrocarbon fuels (e.g., 4 CH₄ + 7 O₂ → 2 CO₂ + 2 CO + 8 H₂O). Faulty and insufficiently maintained gas-fired heaters in livestock buildings may therefore cause performance losses (Morris et al., 1985), abortions (Pejsak et al., 2008) or even a suffocation risk for animals when hemoglobin is excessively engaged due to the comparably higher affinity of CO to hemoglobin than inhaled oxygen. Other sources include vehicles (e.g., tractors used in cubicle houses for feeding purposes) or fuel-operated electricity generators for emergencies (e.g., ventilation failure), from which exhaust gases may enter the livestock building.

Livestock-related greenhouse gases (GHG) such as methane (CH₄: colorless, odorless) and nitrous oxide (N₂O: colorless, sweetish odor) contribute to climate change (IPCC, 2013), whereas their toxicological potential is negligible. In the case of CH₄, the ruminal fermentation predominantly observed in cattle and sheep is the most important biochemical process within livestock production that causes considerable amounts of this gas to be produced by methanogenic prokaryotes (methanogens). Other CH₄ sources belong to organic materials, such as manure, which is decomposed in oxygen-deprived conditions (Smith et al., 2008). Methane is also released by monogastric animals. However, considerable amounts are only derived from fermentative processes in the hindgut of pigs. Because CH₄ emissions caused by pigs account for only approximately 1% of those from dairy cattle, no strategies for reducing such emissions seem necessary (Clemens and Ahlgrimm, 2001).

Nitrous oxide is typically produced by microbial activities in terrestrial and aquatic ecosystems. It is specifically a by-product of the nitrification-denitrification process of N-containing materials found in soils due to fertilization (i.e., mineral fertilizer) and manure decomposition (e.g., livestock buildings with bedding material: straw and animal excreta, storage of manure and applications for plant cultivation). Nitrification is the biological oxidation of NH₄⁺ or NH₃ via hydroxylamine to nitrite (NO₂⁻) or nitrate (NO₃⁻) with a subsequent denitrification, which normally results in the production of gaseous nitrogen (N₂). This nitrogen cycle is microbiologically and aerobically triggered by the genera Nitrosomonas (NH₃/NH₄⁺ → NO₂⁻) and Nitrobacter (NO₂⁻ → NO₃⁻) (Butterbach-Bahl et al., 2011) and further maintained by abundant and ubiquitous bacteria, such as Pseudomonas spp. or Flavobacterium spp., which denitrify the previous intermediate compounds to N₂ under mostly anaerobic conditions (Carlson and Ingraham, 1983; Pichinoty et al., 1976). The magnitude of the N₂O losses depends on several physical and chemical factors, such as the oxygen concentration, carbon availability, pH value or temperature (Amon et al., 1999).

Odor is a complex mixture of inorganic (e.g., NH₃, H₂S) and organic (e.g., amines) gaseous agents, which are mainly produced by the decomposition of organic matter. As parts of aerosols, it is not sur...