Manure is primarily a mixture of urine and faeces excreted from pigs that contains undigested dietary compoenets, endogenous end products, excreted excees absorbed nutrients, and indigenous bacteria from the lower gastrointestinal tract of the pig. Manure contains a variety of organic cpmpounds complex to simple in nature, inorganic compounds, and potentially feed additives depending on the makeup of the diet. Pig faeces and urine both contain considerabvle amounts of nitrogen, phosphorus, and other minerals such as calcium, and magnesium. Fecal nitrogen arises from undigested dietary protein, intestinal secretions, sloughed intestinal cells and intestinal bacteria. Urinary nitrogen largely in the form of urea, arises from the breakdown of absorbed dietary amiono acids that are in excess of the amounts needed for lean protein synthesis, and from the normal breakdown of body tissue products.

Numerous compounds have been identified from the anaerobic degradation of livestock manure. Hey have been generally grouped as volatile amines, sulfides, disulfides, orhanic acids, phenols, and more. But more recent analysis have identified 15 specific volatile organic compounds as primaryodour causing compounds from manure. The sensitivity of individul compounds by olfactory threshold detectionvaries widely. In general sulfur-containing compounds are among the group of lowest detection thresholds from manure. A major challenge in identifying specific odourous compounds from manure is that analytically derived gas concentrations and olfactometry are not highly related. Moreover there are confounding effects of mixtures of different compounds on olfactometry detection. Some volatile organic compunds have change chemical form, hus, precise analytical detection and quantification of air samples is also a challenge.