Particulate matter concentrations in two different buildings for laying bens. A first note

Dust concentration, as Particulate Matter (PM2.5 and PM10), was monitored in two different buildings for laying hens in Italy. The first unit, equipped with a traditional system of slurry removal (deep-pit), measured 93x14 m and it housed 60,000 laying hens. The animals were confined in vertical tiered batteries with 5 rows and 6 tiers. The second unit was characterised by a technological system of slurry removal with a low environmental impact, classified as BAT (Best Available Techniques), in which the droppings were dried on ventilated belts. The building measured 80x15 m and it housed 60,000 laying hens. The animals were confined in vertical tiered batteries with 6 rows and 8 tiers. Both the units were ventilated with a negative pressure fan system. The data were collected continuosly every 30 minutes for 34 days in two periods (1 (st) period: August - September; 2 (nd) period: October - November), using the "Haz-Dust EPAM-5000" which works on-line and it gives the results in real time. The instrument was placed near one of the exaust fans. A data logger recorded temperature and relative humidity continuosly or every 30 minutes. The data of PM(2.)5 collected during the V period were higher for the building with the traditional system of slurry removal than for the building with the BAT technique (0.104 mg/m(3) vs 0.027 mg/m(3)). The result was the same for the data of PM10 (0,38 mg/m(3) vs 0.085 mg/m(3)). During the 2 (nd) period the dust concentration was lower in the first building than in the second one (0.06 mg/m(3) VS 0.11 mg/m(3) for PM2,5; 0.2 mg/m(3) vs 0.48 mg/m(3) for PM10). The result was probably linked to the different values of relative humidity registered during the test. Infact, during the 2 (nd) period, in the housing using the BAT technology, the average value of relative humidity was 53-55 % while in the other building was higher (64-67 %). As low dust concentrations are associated to higher values of relative humidity, there was a lower efficiency in dust reduction of the BAT technology during the 2 (nd) period. The very low value of PM2.5 in the building with the deep-pit system was linked to the complete emptying of the pit before the data collection.