Measuring gaseous emissions from stored pig slurry

The study tested the use of dynamic floating chambers to measure emissions factors of ammonia (NH3), nitrous oxide (N2O) methane (CH4) and carbon dioxide (CO2) from stored pig slurry and measured the variations of the emissions in time and space.In 2006, dynamic floating chambers were used for the continuous measurement of gaseous emissions from two experimental tanks filled with fattening pig slurry stored for two summer months and in a pit filled repeatedly with mixed slurry between October and March. To check the influence of air speed on gaseous emissions, each tank was fitted with a chamber : one operating with an air speed at the surface of the slurry of 0.01 m/s, the other with a speed of 1 m/s. To ascertain the spatial variability of the emissions, two identical chambers were used for the pit : one was regularly displaced across the surface of the slurry ; the other was fixed throughout the storage period. The measurements obtained were compared with the nitrogen and carbon input-output mass balances of the slurry. The results indicated that the measured gaseous emissions explained 4 to 38% of the total nitrogen losses and 61 to 285% of the total carbon losses. The use of such dynamic floating chambers is not an appropriate method to evaluate the gaseous emission factors from slurry storage. The kinetics of the emissions underline the importance of measurement periods and their duration to measure emission factors.