J. Dairy Sci. 84:1814–1821 American Dairy Science Association, 2001. Effect of Adding Alum or Zeolite to Dairy Slurry on Ammonia Volatilization and Chemical Composition A. M. Lefcourt and J. J. Meisinger Agricultural Research Service, USDA Animal and Natural Resources Institute Beltsville, MD 20705 ABSTRACT INTRODUCTION Development of cost-effective amendments for treat- Development of cost-effective treatments for animal ing dairy slurry has become a critical problem as the manure has become a critical problem as the number number of cows on farms continues to grow and the of animals raised on farms continues to grow and the acreage available for manure spreading continues to land mass available for manure spreading continues shrink. To determine effectiveness and optimal rates to shrink. The three main nutrient issues for on-farm of addition of either alum or zeolite to dairy slurry, we treatment of manure are: nitrogen (N) loss through measured ammonia emissions and resulting chemical ammonia volatilization, excess phosphorus (P), and the changes in the slurry in response to the addition of balance of N to P (N/P ratio). This study addresses the amendments at 0.4, 1.0, 2.5, and 6.25% by weight. Am- potential for using a chemical additive, alum or zeolite, monia volatilization over 96 h was measured with six to reduce ammonia volatilization and P availability small wind tunnels with gas scrubbing bottles at the from dairy slurry. inlets and outlets. Manure samples from the start and Up to 50% of the N in freshly excreted manure can end of trials were analyzed for total nitrogen and phos- be lost with the conversion of urea, which is a primary phorus, and were extracted with 0.01 M CaCl2, 1.0 M component of urine, to ammonia and the subsequent KCl, and water with the extracts analyzed for ammo- volatilization of the ammonia to the atmosphere (Bus- nium nitrogen, phosphorous, aluminum, and pH. The sink and Oenema, 1998; den Boerb et al., 1990; Muck addition of 6.25% zeolite or 2.5% alum to dairy slurry and Richards, 1983; Phillips et al., 1999). This ammonia reduced ammonia emissions by nearly 50 and 60%, re- loss impacts both agricultural and nonagricultural eco- spectively. Alum treatment retained ammonia by re- systems in terms of a direct loss of plant available N ducing the slurry pH to 5 or less. In contrast, zeolite, to the farmer, a reduced N/P ratio which accelerates P being a cation exchange medium, adsorbed ammonium build-up in soils, and eutrophication in aquatic and low- and reduced dissolved ammonia gas. In addition, alum N input ecosystems through atmospheric transport and essentially eliminated soluble phosphorous. Zeolite also deposition (ApSimon et al., 1987; Asman, et al. 1994, reduced soluble phosphorous by over half, but the mech- 1998; van Breemen et al., 1982). Volatilized ammonia anism for this reduction is unclear. Alum must be care- also reacts with sulfur compounds released from com- fully added to slurry to avoid effervescence and excess bustion of carbon fuels to form the majority of the 2.5- additions, which can increase soluble aluminum in the µ size particulates. These particulates are of particular slurry. The use of alum or zeolites as on-farm amend- concern for human health and are the subject of pending ment to dairy slurry offers the potential for reducing regulation (Confined Livestock Air Quality Commit- ammonia emissions and soluble phosphorus in dairy tee, 2000). slurry. Phosphorus is a concern because manure is typically (Key words: amendments, ammonia volatilization, spread on agricultural fields at rates in excess of that dairy manure, phosphorus) needed to support crop growth, which has resulted in Abbreviation key: TKN = total Kjeldahl nitrogen, the accumulation of excess soil P. Manures spread on TKP = total Kjeldahl phosphorous. fields commonly contain N/P ratios of 3/1 to 5/1, while crops require N/P ratios of about 8/1 (Beegle, 1999; Sharpley, et al., 1998). Thus, using manures to meet crop N requirements will simultaneously add excess P Received December 26, 2000. to soils and cause soil-test P levels to rise. High soil- Accepted March 27, 2001. Corresponding author: A. M. Lefcourt; e-mail: alefcour@anri. test P levels have been found to contribute P to fresh usda.gov. water resources through direct erosion of high P sedi- 1814 MANURE TREATMENT 1815 ment and surface runoff of P from high soil-test P areas Table 1. Chemical composition of zeolite.1 (Sharpley et al., 1998; Sims, 1993; Snyder et al., 1993). Chemical Percent Two major factors contributing to the low N/P ratio in SiO 65.35 manure are the loss of excreted N through ammonia 2 Al2O3 12.72 volatilization and the presence of excess P in the diets Na2O 2.60 of farm animals. K2O 3.62 CaO 2.14 One common strategy for treating manure is the addi- MgO 0.59 tion of amendments such as acidifying agents (alum, Fe2O3 1.51 iron salts, mineral acids), sequestering agents (zeolites, TiO2 0.05 P2O5 0.02 flocculents), or agents that bind P (alum, calcium salts). MnO 0.02 However, for an amendment to be commercially viable, 1Zeolite from Nicole Mountain, color white, 200 mesh, ammonium it must be reasonably priced, and the benefits must exchange capacity 1.84 to 1.96 meg/gm, and principal mineral clinop- outweigh any potential adverse environmental effects. tilolite. Provided by Southwest Mining Group, Inc., Laguna Hills, Two amendments that potentially meet these criteria CA. are alum and zeolite. Alum is commonly used to remove P during sewage treatment; hence, it is widely available at reasonable cost. It is currently used as a litter amend- Research Center after 1 h of agitation. Cows in the barn ment in the poultry industry, primarily to chemically were fed a TMR and manure was collected using a sequester P (Maurice et al., 1998; Moore and Miller, continuously running mechanical scraper that scraped 1994). However, it can also lower ammonia emissions the manure up to 100 m before depositing it in the from poultry houses (Moore, 1998). Alum has also been holding pit. Bedding consisted of a small amount of used as an amendment in feedlots (Dao, 1999), during sawdust, and the DM content of the slurry ranged from composting of poultry manure (Kithome et al., 1999), 9 to 11%. and to reduce P content in dairy wastewater (Jones and On four separate dates, a bulk sample of about 24 L Brown, 2000). Zeolite is a silicate clay mineral widely of slurry was collected and subdivided into appropriate available in the western United States and Mexico. lots for use as untreated controls, or for treatment with Zeolite is a cation-exchange medium that has been used alum or zeolite. Six wind tunnels were available for to reduce ammonia in water (Kithome et al., 1998) and studying ammonia volatilization for each trial. For trial in products such as kitty litter to reduce ammonia emis- one, the treatments consisted of 0.4, 1.0, 2.5, and 6.25% sions from urine. Zeolite has been used as an amend- alum (commercial grade, granular aluminum sulfate, ment to poultry litter (Maurice et al., 1998), in anaero- Al (SO ) ؒ14H O) along with two controls with 48.5% bic reactors treating cattle manure (Borja et al., 1996), 2 4 3 2 no additives. Additions were calculated on a weight during composting of poultry manure (Kithome et al., basis. For trial two, zeolite (Table 1) was used at the 1999), and as a filtration agent in deep-bedded cattle same rates instead of alum. For trial 3, 2.5 and 6.25% housing (Milan et al., 1999). The primary cost compo- alum and zeolite were used along with two controls. In nent for zeolite is the cost of shipping. The efficacy of trial four, replicates of 2.5% alum and zeolite were used alum or zeolite as an amendment to dairy slurry has along with two controls. The first two trials identified not been tested. optimum levels of alum and zeolite based on their am- The general objective of this research was to evaluate monia loss characteristics, while the last two trials pro- the potential benefits and suitability of alum and zeolite as on-farm manure treatment amendments for dairy vided a direct comparison of alum versus zeolite on slurry. Specific objectives were: 1) to determine the opti- ammonia loss. After adding the appropriate amend- mum concentrations of alum and zeolite for reducing ment at the desired rate, the slurry was mixed with a ammonia losses from dairy slurry, 2) to quantify the large dough mixer. Each slurry treatment was then effectiveness of these amendments on ammonia volatil- subdivided into four 1-L containers and three metal ization, 3) to assess the effects of these amendments on pans for DM determination. Two of the containers were slurry properties such as pH, soluble P, exchangeable placed on ice and transported to the wind tunnel site ammonium-N, and water soluble Al, and 4) to elucidate within 2 h of collection and treatment, the third was ° the chemical basis for treatment effects. put in refrigerator (4 C) for short-term storage before analysis, and the last container was stored at −20°C. MATERIALS AND METHODS Manure Collection and Treatment Ammonia Volatilization Slurry was collected from the holding pit at the base Ammonia volatilization was assessed with a system of the free-stall dairy barn at the Beltsville Agricultural of small mobile wind tunnels described in detail by Journal of Dairy Science Vol. 84, No. 8, 2001 1816 LEFCOURT AND MEISINGER Meisinger et al.