FLUX CHAMBER VALIDATION FOR AMMONIA MEASUREMENT VERSUS WHOLE ROOM EMISSION

The design of a flux chamber affects accurate ammonia measurements from manure. The objective was to compare dairy manure ammonia emissions from a whole-room mass balance calculation (ventilation rate x gas concentration) versus emission measurements performed within that room using portable flux chambers. Assessment focused on two chamber measurement systems: a widely-accepted U.S. Environmental Protection Agency (EPA) steady-state flux chamber and a non-steady- state recirculation flux chamber designed specifically at Penn State for ammonia measurements from manure. To simulate naturally-ventilated animal building environment in the test room an air velocity of 0.3 m s -1 was established at 8 cm above the floor. During trials fresh dairy manure was uniformly spread over the room floor. Ammonia concentration (infrared photoacoustic analyzer) multiplied by room air flow rate (duct traverse of exhaust fan) calculation was compared with the ammonia emission rate calculated using accepted formulas appropriate for each flux chamber type. Emissions were evaluated over 9 - 20 o C and conducted 18 hours after manure application to establish equilibrium emission conditions. The Penn State flux chamber offered more accurate emission estimates compared to the EPA device by measuring 90% to 119% of ammonia emissions of the whole room. This compared to EPA chamber measures of 14% or 50% of the emissions of the whole room at sweep air flow rates intervals of, respectively, 3.25 L min -1 (manufacturer recommendation) to 10.0 L min -1 (maximum available). This work suggests that the EPA chamber method, although universally recognized in USA emission evaluations, is not as suitable for sources with high gas emissions (manure) versus its previous uses with lower emission sources (soil, industrial, etc.).