Field measurements of ammonia (NH3), nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) were made from raw pig slurry storage, from different biological aerobic treatments and from stores holding the treated products. Biological treatments consisted of intermittent aeration by (i) submerged ejector aerator, (ii) surface aerator and (iii) fine-bubble diffuser. Emissions were measured from the solid separated fraction of raw slurry and from whole aerated slurry and from supernatant and sludge following sedimentation. Measurements of gaseous emissions were made under field conditions using the dynamic chamber technique for all liquids (raw slurry, reactors and treatment by-products) and by enclosing the heap of solid separated fraction in a large polytunnel with air drawn up by a fan. The results showed that the emissions of CH4, CO2 and NH3 were greater for the non-aerated effluents (raw slurry and separated solid fraction) which have a higher ammonium and organic matter level than for treatment by-products. N2O was only detected above the biological reactor and the concentration was low (