The effect of compost and earthworms casts biofilters on gaseous emissions from dairy manure stacks

Abstract

Stacked dairy manure emits greenhouse gases N2O, CH4, and CO2, as well as NH3. Biofilters consist of an organic media where microbial activity could catabolise volatile compounds. This study evaluates the effect of biofiltration on the level of gaseous emissions from stacked manure. A 1:1 volume ratio of free stall dairy manure and saw dust were stacked in a 50 m3, 1 meter high wooden structure. The surface of the resulting manure stack was covered with 12 treatments. Eight were biofilters varying in their content, (compost or earthworm casts), thickness, and moisture level. They were created by layering 2 Curlex® sheets (a woven straw cover normally used for erosion control) with organic material sandwiched between the two sheets. Four treatments consisted of a layer of Curlex®, moistened or not, a layer of Bio Curlex®, a variant of Curlex®, and a control. Treatments were evaluated by their NH3, N2O, CH4, and CO2 emission rates measured with a photoacoustic sensor coupled with a flux chamber, and by their respiration rate. Results showed a significant treatment effect on NH3, N2O, CH4, and CO2 emission rates. Emission rates of NH3, N2O, CH4, and CO2 gases were significantly correlated to the respiration rate of the biofilter filling. The emission rates of NH3 and N2O and CH4 gases were also correlated to ambient temperatures, and temperatures of the manure stack at different depths, recorded in a companion study. Results indicate the potential of biofilters to mitigate greenhouse gases and ammonia emissions from manure storage in animal facilities.