Liquid manure (slurry) storages are significant sources of atmospheric methane (CH₄). A surface crust may form naturally, or an artificial cover of, e.g., straw, expanded clay or a polyethylene sheeting can be established. Previous suggestions that methane-oxidizing bacteria could thrive in this environment were recently confirmed [Petersen, Amon & Gattinger, J. Environ. Qual. vol. 34, 455-461]. This presentation will describe new observations on the occurrence of methane oxidation in surface crusts, and it will discuss the potential of the process to control emissions to the atmosphere. Surface crust samples were collected at two pig farms and six dairy farms in late autumn. Methane oxidation was observed in all materials except for an expanded clay product (Leca) sampled from a pig slurry storage. There was a significant increase in methanotrophic activity with increasing methane concentrations from 500 to 50,000 ppmv CH₄, and maximum fluxes ranged from 1 to 4.5 g CH₄ m^-2 d^-1. This potential is comparable to the activity observed in soil environments such as rice paddies, where re-oxidation of methane produced in the sub-soil may be extensive. It implies that methanotrophic acitivity could also mediate against methane emissions from slurry storages, although currently the effect is probably restricted by such factors as incomplete coverage, ebullition and climatic conditions. Work is in progress to optimize storage conditons for stimulation of methane oxidation activity. Preliminary results with aeration control based on on-line GC analysis of the headspace gas phase composition will be presented and discussed in the context of greenhouse gas mitigation.