LABORATORY EVALUATION OF THE DUST-EMISSION POTENTIAL OF CATTLE FEEDLOT SURFACES

Abstract

A laboratory apparatus was developed for measuring the dust-emission potential of cattle feedlot surfaces asaffected by manure surface characteristics. A feedlot surface was simulated with a layer of dry, loose, sieved feedlot manure,either with or without a compacted soil layer underneath. The vertical action of the cattle hoof was reproduced by droppinga steel weight onto the manure surface. High-volume samplers for PM10 (particulate matter smaller than 10 .m aerodynamicequivalent diameter) were used to collect suspended PM10. The effects of kinetic energy of the falling weight, manure depth,manure moisture content, bulk density, and surface amendment (sawdust, wheat straw, and surface water application) wereinvestigated. For each manure depth, PM10 emission was directly related to the kinetic energy of the falling weight. For eachweight drop, PM10 emission did not differ significantly with manure depth. In addition, PM10 emission was inversely relatedto the manure moisture content. Compaction of the manure surface reduced PM10 emission. Increased amounts of water,sawdust, or wheat straw to the manure surface also significantly decreased PM10 emission in initial tests, butdislodging/displacement of wheat straw and penetration of the wetted surface crust by the falling weight increased theemission potential for subsequent tests. The weight drop test chamber developed is a simple and repeatable method that canbe used to compare relative effectiveness of different dust abatement measures. While the measurements are reproducible, thevertical action of the cattle hoof is highly simplified; thus, the WDTC might not fully reproduce the actual vertical action ofthe cattle hoof on a feedlot surface. In addition, the resulting aerosol may not have similar physical characteristics as thoseof dust emitted from feedlots.