Reduction of odor and odorant emissions from slurry stores by means of straw covers.

Swine (Sus scrofa) slurry stored in open storages is a source of airborne contaminants. A customary practice for ammonia and odor control consists of covering the surface of the slurry with floating materials, such as straw. Although straw covers have been proven to generally reduce gaseous emissions, more knowledge is needed regarding how age, moisture content, and microbiological development of the straw cover affect the emissions of odor and odorants to develop recommendations for the practical use of straw covers. This study compiles data on odor concentration and odorants above swine slurry covered by straw of different ages and moisture contents, during a 9 wk laboratory scale study. The results showed that aged straw covers significantly reduced emissions of ammonia (by 99%), dimethyl sulfide (by 81%), phenol (82%), p-cresol (by 95%), skatole (by 98%), and benzylalcohol (by 97%), while no significant differences were found between uncovered and covered slurry for emission of odor, hydrogen sulfide, volatile fatty acids, dimethyl disulfide, and indole. The moisture content of the straw cover neither affected emissions of odor nor odorants. This study suggests that the main mechanism for odor and odorants emission reduction from straw covered slurry is as a physical barrier and not as a biofilter. However, the reduction in emissions of specific gases (such as ammonia, dimethyl sulfide, p-cresol, and benzyl alcohol) appears to be also caused by the straw cover acting as a biofilter.

Greenhouse gas microbiology in wet and dry straw crust covering pig slurry.

Liquid manure (slurry) storages are sources of gases such as ammonia (NH(3)) and methane (CH(4)). Danish slurry storages are required to be covered to reduce NH(3) emissions and often a floating crust of straw is applied. This study investigated whether physical properties of the crust or crust microbiology had an effect on the emission of the potent greenhouse gases CH(4) and nitrous oxide (N(2)O) when crust moisture was manipulated ("dry", "moderate", and "wet"). The dry crust had the deepest oxygen penetration (45 mm as compared to 20 mm in the wet treatment) as measured with microsensors, the highest amounts of nitrogen oxides (NO(2)(-) and NO(3)(-)) (up to 36 mumol g(-1) wet weight) and the highest emissions of N(2)O and CH(4). Fluorescent in situ hybridization and gene-specific polymerase chain reaction (PCR) were used to detect occurrence of bacterial groups. Ammonia-oxidizing bacteria (AOB) were abundant in all three crust types, whereas nitrite-oxidizing bacteria (NOB) were undetectable and methane-oxidizing bacteria (MOB) were only sparsely present in the wet treatment. A change to anoxia did not affect the CH(4) emission indicating the virtual absence of aerobic methane oxidation in the investigated 2-mo old crusts. However, an increase in N(2)O emission was observed in all crusted treatments exposed to anoxia, and this was probably a result of denitrification based on NO(x)(-) that had accumulated in the crust during oxic conditions. To reduce overall greenhouse gas emissions, floating crust should be managed to optimize conditions for methanotrophs.

Reduction of ammonia emission by shallow slurry injection: injection efficiency and additional energy demand.

Ammonia (NH3) emission from livestock production causes undesirable environmental effects and a loss of plant-available nitrogen. Much atmospheric NH3 is lost from livestock manure applied in the field. The NH3 emission may be reduced by slurry injection, but slurry injection in general, and especially on grassland, increases the energy demand and places heavy demands on the slurry injection techniques used. The reduction in NH3 emission, injection efficiency, and energy demand of six different shallow slurry-injection techniques was examined. The NH3 emission from cattle slurry applied to grassland was reduced by all the injectors tested in the study, but there were major differences in the NH3 reduction potential of the different types of injectors. Compared with the trailing hose spreading technique, the NH3 loss was reduced by 75% when cattle slurry was injected using the most efficient slurry injection technique, and by 20% when incorporated by the least efficient injection technique. The reduction in NH3 emission was correlated with injection depth and the volume of the slot created. The additional energy demand for reducing ammonia emissions by slurry injection was approximately 13 000 kJ ha(-1) for a 20% reduction and 34 000 kJ ha(-1) for a 75% reduction. The additional energy demand corresponds to additional emissions of, respectively, 5.6 and 14.5 kg CO2 per ha injected.

Demographics of enuresis patients attending a referral centre.

OBJECTIVE: To study and compare the demography of enuretic children 7-16 years old attending a tertiary referral centre for childhood urinary incontinence, with that of normal children and what is generally known about enuretics from population-based studies. METHODS AND MATERIALS: This was a retrospective analysis of data compiled from 298 enuretic patients referred to The Centre of Child Incontinence, Aarhus University Hospital, Skejby, Denmark, and 53 healthy controls. Data was obtained by conducting standardised questionnaire interviews. Patients were stratified according to accompanying symptoms and severity of enuresis. Statistical analysis of the results was then performed. RESULTS: Two hundred and ninety-three patients had sufficient data registered to allow reliable analysis. Male-female ratio was 2.2:1. Primary and secondary enuresis was found in 87.4% and 11.6% of the patients respectively. Enuresis was associated with a reported history of bronchial asthma (p < 0.05), verified allergy (p < 0.05) and a positive family history of the same disorder (p < 0.01). No association with psycho-developmental factors was evident. Approximately 98% of the patients had undergone some form of therapy at presentation. 74.1% of the patients had pure monosymptomatic enuresis, 16.4% had day and night time incontinence, while the remaining 9.6% had nocturnal incontinence combined with other lower urinary tract symptoms other than daytime wetting. CONCLUSIONS: The demography of our patient population was, with a few exceptions, within the confines of what has previously been reported. Our results also reaffirmed the heterogeneity of enuretic patients.

The circadian rhythm of urine production, and urinary vasopressin and prostaglandin E2 excretion in healthy children.

PURPOSE: In adults and adolescents the transition from day to night is followed by a pronounced decrease in diuresis, as well as reduction in the amount of osmotically active substances excreted. We investigate the circadian variations in urine production in healthy children 3 to 14 years old. MATERIALS AND METHODS: A total of 92 children completed urine collections in 2 consecutive days to be analyzed for electrolytes, urea, creatinine, osmolality, vasopressin and prostaglandin E2. RESULTS: We found a marked reduction in urine output during the night (43.41 +/- 18.53 to 25.69 +/- 12.71 ml per hour) accompanied by a decrease in the amount of electrolytes excreted (sodium 4.44 +/- 2.09 to 2.66 +/- 1.55 mmol per hour and potassium 2.38 +/-0.96 to 0.90 +/- 0.54 mmol per hour). Age and gender did not influence the observed circadian rhythm in the quantity and quality of urine production. Urinary excretion of vasopressin did not seem to reflect the circadian variations previously described for the plasma levels of the hormone. Prostaglandin E2 showed a clear circadian variation with a 30% decrease at night (32.2 +/- 19.0 to 22.0 +/- 12.6 ng/mmol creatinine). CONCLUSIONS: Healthy children exhibit pronounced circadian variations in the amount and composition of urine output with a decrease in nocturnal diuresis and excretion of osmotically active solutes. In the age range of 3 to 14 years neither age nor gender seems to affect this rhythm. Vasopressin-to-prostaglandin E2 excretion ratio appears to be of importance for regulation of urine production.