Sporulation and implications for composting food waste

Well managed composting is generally a safe method for processing organic wastes and generating a product that has beneficial uses. However, there is uncertainty regarding the safety of composts produced from high-risk organic wastes. High-risk organic wastes are wastes that may contain contaminants (biological, physical or chemical) that render the waste difficult to process and are likely to pose unacceptable residual risks after suboptimal processing. In this article, we examine the environmental stressors present during the composting process and how they impact the fate of spore-forming bacteria. For example, promoting sporulation of spore-forming bacteria early in the composting process by maintaining a steady but slow rise in temperature may increase their removal. As a result, the composting process could be optimised to maximise the removal of pathogenic spore-forming bacteria otherwise likely to survive the composting process. A hazard analysis and critical control point (HACCP) is proposed that utilises the timing of pathogen inactivation, as well as a multibarrier approach to ensure that inactivation during composting does not only rely on a single operational parameter. This is a systematic and flexible approach which could offer composters a practicable and efficient system to reduce spore-forming bacteria as more high-risk organic wastes are diverted from landfills to be composted.