2016, Walkden-Brown, Steve W, Laurenson, Yan, Islam, A Fakhrul, Dunlop, M, Wells, B A

Heaping of used poultry litter produces elevations in temperature that lead to a significant reductions in pathogen load, analogous to pasteurisation. The speed and degree of heating varies with depth in the heap and with a range of factors that can be influenced by management. These include heap size, moisture content, turning and covering. In broad terms smaller heaps heat more quickly and are more appropriate for shorter pasteurisation periods. Turning of heaps is only beneficial for pasteurisation periods of longer than 7 days and potentially detrimental for periods of 6 days or shorter. On the other hand the benefits of covering heaps are reduced with longer pasteurisation periods. Addition of moisture is rarely needed and never required if covers are used. This paper summarises the effects and interactions between these practices and concludes with a brief suggested operating procedure.

2016, Laurenson, Yan, Islam, A Fakhrul, Dunlop, M, Cressman, M D, Walkden-Brown, Steve W

Litter pasteurisation through the partial composting of meat chicken (broiler) litter reduces pathogen carryover between grow-outs. Pathogen inactivation is primarily via the effects of temperature; however, our understanding of factors affecting the temperature profile of composting heaps is incomplete. Temperature profiles at differing depths within heaps subjected to a wide range of treatments on different farms were used to construct a mathematical model empirically describing the impact of ambient temperature, heap dimension, initial moisture content, covering and turning on temperatures within a composting heap. This model was incorporated into an Excel® workbook with an appropriate user-interface and customised inputs and outputs to create a decision support tool to assist with the appropriate design of litter pasteurisation practices.

2016, Walkden-Brown, S W, Islam, A F, Laurenson, Yan, Dunlop, M, Wells, B A

Heaping of used poultry litter reliably induces significant elevations in temperature due to the actions of variety of aerobic bacteria and fungi. Temperatures typically rise to over 50°C in 1- 4 days and may peak at more than 60°C. These temperatures are sufficient to reduce or eliminate a range of pathogens giving rise to the term 'pasteurisation'. A common target for litter pasteurisation is heating to 55°C for a minimum of 3 days. Factors influencing heating potential include carbon to nitrogen ratio, moisture content, oxygen availability and to a lesser extent pH. This paper summarises the key underlying principles and factors influencing litter pasteurisation while a companion paper deals with practices to optimise it.