Methane emissions from swine houses in North Carolina

Gaseous methane (CH₄) emissions were determined during the winter and summer from `farrow-to-finish' (FF) swine production houses and during the summer from a `farrow-to-wean' (FW) house in 1998 in the coastal plains of North Carolina. The houses were instrumented with sensors to determine cycling of the individual forced-ventilation fans. Laser spectrometry was used to measure CH₄ concentration differences between the intake and exhaust points of the houses. Differences in CH₄ concentrations were combined with fan operation data to calculate CH₄ fluxes from the houses. During the cold winter measurement period, CH₄ fluxes averaged 6.9 g $\text{CH}{}_4\text{animal}{}^{\mathrm{-1}}\text{d}{}^{\mathrm{-1}}$ in the FF house. During summer measurement periods, CH₄ fluxes were much greater and averaged 33 and 46 g $\text{CH}{}_4\text{animal}{}^{\mathrm{-1}}\text{d}{}^{\mathrm{-1}}$ from the FF and FW houses, respectively. The much larger emissions during the summer than winter, indicate that CH₄ house emissions were primarily from fresh feces and the underground storage/wash pits containing lagoon effluent; and not directly from the animals since temperature would have little affect on direct animal emission. Emission factors based on animal units (au) of 454 kg animal⁻¹ were much greater at the FW farm with a pull-plug waste management system (7–8 day wash cycle) than at the FF farm with a periodic flush system (8 h wash cycle).