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Valorisation of poultry litter to compost: an assessment of the pathogen reduction potential

Author: Nafiisa Sobratee, University of Kwazulu-Natal, Pietermaritzburg, South Africa

Date: 28/03/2014

Introduction:

Dr Sobrateewon the first prize in the Women in Science competition. She considers the identification of the weak points, in terms of sanitisation status, that allow bacterial pathogens to proliferate during composting the most relevant result of her project. ‘Optimised practices of composting, as a component of both conservation agriculture and conventional farming, is one of the solutions to Africa’s soil fertility crisis.’ She continued; ‘being at the first place in the competition gives me a legitimate sense of fulfilment with respect to the relevance of my research. It has also instilled in me the confidence that I can make a difference in the field of bio-resource management.’ Dr Sobratee sees herself in five years’ time working in academia in Mauritius, being engaged in both teaching and learning and in research, whereby teaching and learning activities will be driven and informed by her research and development work.    


 

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Composting of biodegradable agricultural residues has two advantages in Africa: (i) improving soil properties and crop productivity in low input agriculture; and (ii) developing compost production as a side business to promote youth and women entrepreneurship. Even though pathogen elimination by composting has been well documented, indicators used to determine if pathogens have been eliminated vary widely principally due to the highly dynamic singularity of the composting system in terms of feedstock characteristics, process variables monitored and pile management. The aim of the study was to demonstrate the capacity of composting in transforming poultry litter into a safe and pathogen-free soil improver.   

Measurable approaches were used to evaluate composting- driven stabilisation and develop benchmarks. They included (i) examination of the survival of coliforms in windrows consisting of spent poultry litter amended with sugarcane bagasse; and (ii) the sanitization potential in poultry litter composting: decomposition rate, survival kinetics of faecal bacteria indicators, quantitative exposure assessment, and determination of re-growth potential. The results of the decomposition parameters and maximum specific growth rates of inoculated bacteria showed that re-growth may be triggered at the start of compost maturation stage. Simple process control strategies to mitigate this effect included: moisture adjustment to prevent drying off during the high-temperature phase and turning of compost piles to expose all feedstock to composting temperatures and aeration.   

These findings are of primary importance for hygienic process control monitoring in the context of Best Management Practices to produce a safe and valuable conditioner that improves soil fertility. Two oral presentations were delivered during the Research Week organized by the University of Mauritius in 2008. The entire research output formed part of a PhD thesis and has produced four peer reviewed articles in high impact journals and two book chapters.  

28/03/2014