Previous research has examined the impacts of AD (anaerobic digestion) on a range of common crop pests and diseases, and the risks from these are thought to be low, particularly for AD systems that incorporate a discrete pasteurisation step. This project was initiated to confirm and add to published data.
As explained in the full report, pasteurisation was shown to represent an effective treatment for reducing the survival of most organisms tested. The experiments found that many did not survive AD at 37.5°C for more than ten days, although some survived for longer.
The most resilient organism was found to be powdery scab (Spongospora subterranea), which was found to be capable of surviving AD for up to 15 days, but not longer. Where feedstocks had been pasteurised, Spongospora subterranea could not be detected after three subsequent days of AD. The similar organism club root (Plasmodiophora brassicae) was found to be less resilient.
Several organisms were tested in both continuous and batch AD systems (tomato seed and F. culmorum). These showed similar but not identical results, indicating that there is some variation between the systems.
Managing the risk from crop pests and diseases does not automatically require pasteurisation. We have also explored possible alternatives to the standard pasteurisation approach, taking into account the approaches taken to pasteurisation in other industries and other European countries. A separate report is available on this.
This research provides an understanding of the fate of a range of crop pests and diseases in anaerobic digestion systems, should they accidentally happen to be present in feedstocks. However, the research does not support the use of AD as a treatment option for larger loads of crops known to be infected with a crop pest or disease. Further research would be advisable for anyone considering using AD in this way.