Do Effective Micro-Organisms Affect Greenhouse Gas Emissions from Slurry Crusts?

Slurry crusts form on the slurry surface and act as a primary barrier to gaseous emissions and could also be a zone where CH4 is consumed by methane-oxidising bacteria present. However, slurry crusts have also been reported as sources of nitrous oxide emissions. This study evaluated methane oxidation rate and nitrous oxide emissions from a 8 months developed slurry crust followed by 8 weeks application of a mixed microbial consortia (effective microorganism; EM®). There was no clear evidence of CH4 oxidation following EM® application. Whilst there was no significant reduction of N2O fluxes from EM®-treated crusts, there was a tendency for lower N2O emissions from EM®-sprayed crusts. N2O emissions were greater than CH4 consumption, resulting in net greenhouse gas (GHG) emissions of between 13.8-46.7 mg CO2 eq. g-1 DM hr-1. We conclude that it is important to consider net GHG emissions (CO2 eq.) when reporting CH4 oxidation from slurry crusts.