Emissions of Sulfur‐Containing Odorants, Ammonia, and Methane from Pig Slurry: Effects of Dietary Methionine and Benzoic Acid

Abstract

Supplementation of benzoic acid to pig diets reduces the pH of urine and may thereby affect emissions of ammonia and other gases from slurry, including sulfur-containing compounds that are expected to play a role in odor emission. Over a period of 112 d, we investigated hydrogen sulfide (H(2)S), methanethiol (MT), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS), as well as ammonia and methane emissions from stored pig slurry. The slurry was derived from a feeding experiment with four pig diets in a factorial design with 2% (w/w) benzoic acid and 1% (w/w) methionine supplementation as treatments. Benzoic acid reduced slurry pH by 1 to 1.5 units and ammonia emissions by 60 to 70% for up to 2 mo of storage, and a considerable, but transitory reduction of methane emissions was also observed after 4 to 5 wk. All five volatile sulfur (S) compounds were identified in gas emitted from the slurry of the control treatment, which came from pigs fed according to Danish recommendations for amino acids and minerals. The emission patterns of volatile S compounds suggested an intense cycling between pools of organic S in the slurries, with urinary sulfate as the main source. Diet supplementation with methionine significantly increased all S emissions. Diet supplementation with benzoic acid reduced emissions of H(2)S and DMTS compared with the control slurry and moderately increased the concentrations of MT. Sulfur gas emissions were influenced by a strong interaction between methionine and benzoic acid treatments, which caused a significant increase in emissions of especially MT, but also of DMDS. In conclusion, addition of 2% benzoic acid to pig diets effectively reduced ammonia volatilization, but interactions with dietary S may increase odor problems.

Analysis of the effect of dietary protected organic acid blend on lactating sows and their piglets

“…It is possible that, with a higher proportion of protected organic acid blend, NH 3 , mercaptan, and hydrogen sulphide emission reduction would have been significant. According to Eriksen et al (2010), 2% benzoic acid supplementation in the diet of pigs reduced ammonia emissions by 60-70%. The noxious bacterial metabolites and ammonia were reduced by acidifiers with the reduction in pathogen concentration (Dibner and Buttin, 2002).…”

Review of substances/agents that have direct beneficial effect on the environment: mode of action and assessment of efficacy

“…Analysis of livestock excreta identified a large number of different malodorous compounds. Eriksen et al (2010) divided these chemicals into four main groups: (i) volatile fatty acids; (ii) indoles and phenols; (iii) ammonia and volatile amines; and Review of feed additives and their direct beneficial environmental effects EFSA supporting publication 2013:EN-440 29…”

“…There are two main variations: (i) manure and slurry storage systems can be artificially created by mixing urine and faeces in amounts proportional to the measured excretion (e.g. Eriksen et al, 2010;Canh et al, 1998) and (ii) small (i.e. just of sufficient size to collect the animal waste deposited during the experimental sampling period) storage pits can be constructed beneath the pen or cubicle of each individual animal and used to simulate larger scale facilities (e.g.…”

“…Gas analysers were a common approach for ammonia (e.g. Eriksen et al, 2010). Milić et al (2005) used standard colorimetric approaches (see Section 3.3.4) to determine ammonium, nitrate and nitrite ions.…”

“…Milić et al (2005) used standard colorimetric approaches (see Section 3.3.4) to determine ammonium, nitrate and nitrite ions. Eriksen et al (2010) used a gas chromatograph fitted with an amperometric sulphur detector of VOC compounds.…”