Direct measurements of the ozone formation potential from livestock and poultry waste emissions

The global pattern of expanding urban centers and increasing agricultural intensity is leading to more frequent interactions between air pollution emissions from urban and agricultural sources. The confluence of these emissions that traditionally have been separated by hundreds of kilometers is creating new air quality challenges in numerous regions across the United States. An area of particular interest is California's San Joaquin Valley (SJV), which has an agricultural output higher than many countries, a rapidly expanding human population, and ozone concentrations that are already higher than many dense urban areas. New regulations in the SJV restrict emissions of reactive organic gases (ROGs) from animal sources in an attempt to meet Federal and State ozone standards designed to protect human health. The objective of this work is to directly measure the ozone formation potential (OFP) of agricultural animal plus waste sources in representative urban and rural atmospheres using a transportable "smog" chamber. Four animal types were examined: beef cattle, dairy cattle, swine, and poultry. Emissions from each animal plus waste type were captured in a 1 m(3) Teflon bag, mixed with representative background NO(x) and ROG concentrations, and then exposed to UV radiation so that ozone formation could be quantified. The emitted ROG composition was also measured so that the theoretical incremental reactivity could be calculated for a variety of atmospheres and directly compared with the measured OFP under the experimental conditions. The results demonstrate that OFP associated with waste ROG emissions from swine (0.39 +/- 0.04 g-O(3) per g-ROG), beef cattle (0.51 +/- 0.10 g-O(3) per g-ROG), and dairy cattle (0.42 +/- 0.07 g-O(3) per g-ROG) are lower than OFP associated with ROG emissions from gasoline powered light-duty vehicles (LDV) (0.69 +/- 0.05 g-O(3) per g-ROG). The OFP of ROG emitted from poultry waste (1.35 +/- 0.73 g-O(3) per g-ROG) is approximately double the LDV OFP. The measured composition of ROG emitted from animal plus waste sources is nine times less reactive than the current regulatory profiles that are based on dated measurements. The new animal waste ROG OFP measurements combined with adjusted animal waste ROG emissions inventory estimates predict that actual ozone production in the SJV from livestock and poultry (5.7 +/- 1.3 tons O(3) day(-1)) is 40 +/- 10% of the ozone produced by light duty gasoline vehicles (14.3 +/- 1.4 tons O(3) day(-1)) under constant NO(x) conditions.