Improving Air Exchange Rate Calculations by Using Carbon dioxide Balance Method and Estimating Ammonia Emissions from Natural Ventilated Dairy Buildings

Abstract

Determination of air exchange rates plays a key role in estimating ammonia and other contaminated gas emissions from animal buildings. The objectives of this study was to evaluate the effect of cows’ body weight and the production level on the accuracy of air exchange rate calculation from naturally ventilated dairy cow buildings; and to estimate ammonia emission rates using the improved air exchange rate from typical dairy housing in China. Field measurements were carried out in two naturally ventilated dairy cow buildings with different floor types. The production information of each cow was inputted to the CIGR model to calculate the cows’ heat generation and hence to estimate the CO2 production. And then the air exchange rates of the buildings were calculated by using the mass balance method. Comparing with the calculation value by using the simplified method, the total heat production was 17.45% and 8.22% higher for the solid concrete floor and slatted floor individually when considering the production information of dairy cow. The mean ammonia emission rate was 22.66±2.74 g d-1 cow-1 and 10.12±1.91 g d-1 cow-1 for the slatted floor building and solid concrete floor building individually during the measurement. The ammonia concentration was 50% higher for slatted floor building compared with the solid concrete floor building. The results indicated that the individual cow weight and pregnant days should be considered in estimating the air exchange rate using CO2 balance method from naturally ventilated animal housing, especially for the dairy cow of late pregnancy. Otherwise, ammonia emission rate would be underestimated.