Passive reduction of methane emissions from a hog waste lagoon using a floating biofilter syste

Roughly 9 million hogs reside in NC in confined animal feeding operations, where waste is stored in anaerobic, open-air lagoons. Methane (CH4) is an important greenhouse gas emitted from lagoons, but there are no regulatory standards. This study evaluates the efficacy of passive biofiltration as a low-cost approach to reducing CH4 emissions from lagoons. Methane emission from a representative lagoon averaged 4.2 g m-2 d -1. Laboratory experiments showed that a community of CH4 oxidizing bacteria initially colonizing a Growstone support medium and subsequently suspended over the lagoon surface was capable of oxidizing 25% of emitted CH4. However, <1% of the emitted CH4 from the lagoon was oxidized by the CH4 oxidizing community after field deployment. Laboratory experiments indicated high NH3 sensitivity of the methanotroph community initially colonizing the Growstones. Ammonia is universally emitted in open-air waste storage lagoons, suggesting that a passive biofilter is not viable for mitigating CH4 emissions.