Effect of Dietary Protein Levels on Composition of Odorous Compounds and Bacterial Ecology in Pig Manure.

This study was performed to investigate the effect of different levels of dietary crude protein (CP) on composition of odorous compounds and bacterial communities in pig manure. A total of 48 male pigs (average initial body weight 45 kg) fed diets containing three levels of dietary CP (20%, 17.5%, and 15%) and their slurry samples were collected from the pits under the floor every week for one month. Changes in composition of odorous compounds and bacterial communities were analyzed by gas chromatography and 454 FLX titanium pyrosequencing systems, respectively. Levels of phenols, indoles, short chain fatty acid and branched chain fatty acid were lowest (p<0.05) in CP 15% group among three CP levels. Relative abundance of Bacteroidetes phylum and bacterial genera including Leuconostoc, Bacillus, Atopostipes, Peptonphilus, Ruminococcaceae_uc, Bacteroides, and Pseudomonas was lower (p<0.05) in CP 15% than in CP 20% group. There was a positive correlation (p<0.05) between odorous compounds and bacterial genera: phenol, indole, iso-butyric acid, and iso-valeric acid with Atopostipes, p-cresol and skatole with Bacteroides, acetic acid and butyric acid with AM982595_g of Porphyromonadaceae family, and propionic acid with Tissierella. Taken together, administration of 15% CP showed less production of odorous compounds than 20% CP group and this result might be associated with the changes in bacterial communities especially whose roles in protein metabolism.

Effect of slurry treatment approaches on the reduction of major odorant emissions at a hog barn facility in South Korea.

The characteristics of malodor released from piggery excreta samples were investigated by measuring their emission concentrations both before and after such treatments as composting or aeration from field sites. These samples were then collected from field sites and brought into the lab for analysis with the aid of the dynamic flux chamber method. The dominating compounds in the emissions were reduced sulfur compounds, phenol, and indole. The results were examined in terms of two key odor indices: odor intensity (OI) and odor activity values (OAVs), after being grouped by some criteria. When the odor contribution in the composting facility was assessed by the OAV value, methanethiol (53.1%), trimethylamine (TMA) (25.5%), and skatole (10.1%) were dominant in the pretreatment facilities, while skatole (64.7%) and p-cresol (27.9%) in the post-treatment specimens. Likewise, in the liquid treatment facility, hydrogen sulfide (47.4%), p-cresol (26.9%), and skatole (20.2%) were dominant in the pretreatment, while only p-cresol (73.6%) in the post-treatment. In comparison to the composting facility, the liquid treatment facility proved to be more efficient in the treatment of diverse hog-barn-related odorants.

The effects of composting approaches on the emissions of anthropogenic volatile organic compounds: A comparison between vermicomposting and general aerobic composting.

Emission patterns of 13 VOCs were investigated in three types of vermicomposting systems (Eisenia fetida, Metaphire posthuma, and Lampito mauritii) in reference to a traditional aerobic composting system by feeding the systems with mixtures of three materials (coal ash (CA), municipal solid waste (MSW), and cow dung (CD)). On an average, the emission rates of aromatic VOCs (benzene, toluene, xylenes, and styrene) were two to three times higher than all other groups (aldehyde, ketones, esters, and alcohols) from all three types of feeding mixtures. However, the emission rates of aromatic VOCs were generally reduced over time in both aerobic composting and vermicomposting systems. Such reduction in the emission rates was most prominent from Eisenia-treated CD + MSW (1:1), Lampito-treated CD + CA (1:1), and Metaphire-treated CD. The results clearly indicated that the increase in humified organic C fractions (humic acid and fulvic acid) and the microbial biomass present during the biocomposting processes greatly reduced the emissions of VOCs. Hence, the study recommends that vermicomposting of coal ash and municipal solid waste in combination with cow dung in 1:1 ratio is an environmentally gainful proposition.

Estimation of emission factor for odorants released from swine excretion slurries.

In this study, the odorant emission rates from excretory wastes collected in sealed containers from a large swine facility were determined offsite in a laboratory using both raw slurry from ([1] windowless pigpen (WP) and [2] open pigpen (OP)) and treated waste samples ([3] composting facility (CF) and [4] slurry treatment facility (SF)). The emission rates of up to 41 volatile odorants were measured for 100g waste samples (of all four types) in a 0.75L impinger with an air change rate of 8h(-1). The initial emission rates (mgkg(-1)·h(-1)) for the most dominant species from each waste type can be summarized as: (1) WP: NH3 (16.3) and H2S (0.54); (2) OP: H2S (1.78), NH3 (1.69), and p-cresol (0.36); (3) CF: NH3 (7.04), CH3SH (0.30), and DMS (0.12); and (4) SF: NH3 (11.7), H2S (11.7), and p-cresol (0.25). Accordingly, the emission factors for the key odorant (mE, kg·pig(-1))) for fattening pigs in the WP and OP facilities of S. Korea were extrapolated as 3.46 (NH3) and 0.38 (H2S), respectively. The emission factors were estimated assuming exponentially decaying emission rates and slurry production rates obtained from the literature.

Deodorization of pig slurry and characterization of bacterial diversity using 16S rDNA sequence analysis.

The concentration of major odor-causing compounds including phenols, indoles, short-chain fatty acids (SCFAs) and branched chain fatty acids (BCFAs) in response to the addition of powdered horse radish (PHR) and spent mushroom compost (SMC) was compared with control non-treated slurry (CNS) samples. A total of 97,465 rDNAs sequence reads were generated from three different samples (CNS, n = 2; PHR, n = 3; SMC, n = 3) using bar-coded pyrosequencing. The number of operational taxonomic units (OTUs) was lower in the PHR slurry compared with the other samples. A total of 11 phyla were observed in the slurry samples, while the phylogenetic analysis revealed that the slurry microbiome predominantly comprised members of the Bacteroidetes, Firmicutes, and Proteobacteria phyla. The rarefaction analysis showed the bacterial species richness varied among the treated samples. Overall, at the OTU level, 2,558 individual genera were classified, 276 genera were found among the three samples, and 1,832 additional genera were identified in the individual samples. A principal component analysis revealed the differences in microbial communities among the CNS, PHR, and SMC pig slurries. Correlation of the bacterial community structure with the Kyoto Encyclopedia of Genes and Genomes (KEGG) predicted pathways showed that the treatments altered the metabolic capabilities of the slurry microbiota. Overall, these results demonstrated that the PHR and S MC treatments significantly reduced the malodor compounds in pig slurry (P < 0.05).