Review: Ammonia emissions from dairy farms and beef feedlots

Abstract

Hristov, A. N., Hanigan, M., Cole, A., Todd, R., McAllister T. A., Ndegwa, P. and Rotz, A. 2011. Review: Ammonia emissions from dairy farms and beef feedlots. Can. J. Anim. Sci. 91: 1–35. Ammonia emitted from animal feeding operations is an environmental and human health hazard, contributing to eutrophication of surface waters and nitrate contamination of ground waters, soil acidity, and fine particulate matter formation. It may also contribute to global warming through nitrous oxide formation. Along with these societal concerns, ammonia emission is a net loss of manure fertilizer value to the producer. A significant portion of cattle manure nitrogen, primarily from urinary urea, is converted to ammonium and eventually lost to the atmosphere as ammonia. Determining ammonia emissions from cattle operations is complicated by the multifaceted nature of the factors regulating ammonia volatilization, such as manure management, ambient temperature, wind speed, and manure composition and pH. Approaches to quantify ammonia emissions include micrometeorological methods, mass balance accounting and enclosures. Each method has its advantages, disadvantages and appropriate application. It is also of interest to determine the ammonia emitting potential of manure (AEP) independent of environmental factors. The ratio of nitrogen to non-volatile minerals (phosphorus, potassium, ash) or nitrogen isotopes ratio in manure has been suggested as a useful indicator of AEP. Existing data on ammonia emission factors and flux rates are extremely variable. For dairy farms, emission factors from 0.82 to 250 g ammonia per cow per day have been reported, with an average of 59 g per cow per day (n=31). Ammonia flux rates for dairy farms averaged 1.03 g m−2 h−1 (n=24). Ammonia losses are significantly greater from beef feedlots, where emission factors average 119 g per animal per day (n=9) with values as high as 280 g per animal per day. Ammonia flux rate for beef feedlots averaged 0.174 g m−2 h−1 (n=12). Using nitrogen mass balance approaches, daily ammonia nitrogen losses of 25 to 50% of the nitrogen excreted in manure have been estimated for dairy cows and feedlot cattle. Practices to mitigate ammonia emissions include reducing excreted N (particularly urinary N), acidifying ammonia sources, or binding ammonium to a substrate. Reducing crude protein concentration in cattle diets and ruminal protein degradability are powerful tools for reducing N excretion, AEP, and whole-farm ammonia emissions. Reducing dietary protein can also benefit the producer by reducing feed cost. These interventions, however, have to be balanced with the risk of lost production. Manure treatment techniques that reduce volatile N species (e.g., urease inhibition, pH reduction, nitrification-denitrification) are also effective for mitigating ammonia emissions. Another option for reducing ammonia emissions is capture and treatment of released ammonia. Examples in the latter category include biofilters, permeable and impermeable covers, and manure incorporation into the soil for crop or pasture production. Process-level simulation of ammonia formation and emission provides a useful tool for estimating emissions over a wide range of production practices and evaluating the potential benefits of mitigation strategies. Reducing ammonia emissions from dairy and beef cattle operations is critical to achieving environmentally sustainable animal production that will benefit producers and society at large.

Emissions of volatile organic compounds (VOCs) from concentrated animal feeding operations (CAFOs): chemical compositions and separation of sources

“…NH 3 concentrations peaked at around 13:46 local time (LT) and the peak location was northwest of this facility, directly downwind of the animal pens. This is consistent with fresh waste of animals (urine and feces) as the main source of NH 3 within a CAFO facility (Hristov et al, 2011). CO 2 and CH 4 are emitted from animal respiration and eructation of the cattle (Shaw et al, 2007;Sintermann et al, 2014;Owen and Silver, 2015).…”

Effects of dehydrated lucerne and soya bean meal on milk production and composition, nutrient digestion, and methane and nitrogen losses in dairy cows receiving two different forages

“…The lower urinary N for L diets may result from lower digestible N: the ratio between milk and digestible N is 45.1% and 48.0% for SP and L diets, respectively. This shift from urinary to faecal N between SP and L diets (urinary N : faecal N being 48 : 52 to 39 : 61, respectively) may help to reduce nitrous oxide and ammonia emissions, as only a very minor fraction of faecal N is in ammonia form (Hristov et al, 2011), and as urinary urea is rapidly converted into ammonia by faecal urease .…”

Farm-scale nitrogen, phosphorus, potassium and sulfur balances and use efficiencies on Australian dairy farms

“…Particular management strategies are often directed to reduce N losses in particular forms, i.e. nitrate (Ledgard et al 2004), nitrous oxide (de Klein and Eckard 2008) and ammonia (Hristov et al 2011), and while these may assist in meeting particular environmental targets, they may also result in pollution 'swapping' (Stevens and Quinton 2008), i.e. a decrease in one loss pathway may increase another.…”