Composting is a natural biological decomposition process that takes place under aerobic and thermophilic conditions. It can be used for the day-to-day management of mortalities on farms and for carcass disposal in emergency animal disease (EAD) outbreaks. In mortality composting, carcasses are placed in piles or bins together with supplemental carbon sources such as sawdust, litter, straw or wood shavings. Composting is particularly suitable for broiler-farm mortalities and litter. In the case of emergency disease outbreaks, composting can be conducted either inside or outside the poultry house following killing. Composting has been successfully employed for emergency disposal of carcasses in a few cases in North America, but research is lacking on the biosecurity of the process. Composting is a well-established pathogen reduction technology, but process management and heterogenous pile conditions pose particular challenges for validating the microbiological safety of mortality composting. This paper reviews the available information on the biosecurity of mortality composting, identifies potential sources of risk, and highlights emerging research needs. Reports to date of the use of composting in EAD outbreaks are also discussed.