Bioreduction : an alternative strategy for storing fallen stock prior to disposal

Electronic versions


  • Ceri Gwyther

    Research areas

  • PhD, School of Environment, Natural Resources and Geography


Bioreduction has been proposed as an on-farm storage facility for fallen stock prior to final disposal in accordance with the Animal By-Products Regulations, ABPR (EC 1069/2009). In order for bioreduction to be approved under the legislation it must be shown to be biosecure. Therefore, the main aim of this thesis was to assess the risk of pathogen proliferation in the liquor and bioaerosols generated under operational and simulated breakdown scenarios. Secondary objectives consisted of improving the technology and included: determining the efficacy of commercial accelerants in catalysing the bioreduction process; the use of the carbon footprint to identify potential environmental improvements in future vessel designs; and identifying the main physicochemical parameters and enzyme activity associated with bioreduction, in order to more fully understand the underlying biodegradation processes occurring within the vessels. A range of microbiological and molecular techniques were employed to analyse pathogen survival and assess microbial communities and included; traditional culturing, bioaerosol analysis, 16S rRNA sequencing and automated ribosomal intergenic spacer analysis (ARISA). Carbon footprints were analysed using ISO14040 Life Cycle Assessment guidelines, greenhouse gas emissions using a portable gas meter and physicochemical and enzyme assays using standard techniques, often based on soil or compost protocols in the absence of specific bioreduction methods. Whilst there is always room for vessel design improvement such as using solar energy and determining loading capacity to reduce foaming, the technology has repeatedly shown to reduce the volume of waste to be ultimately disposed and has gained favour within the livestock industries. Bioreduction has also shown to be biosecure in both laboratory and field settings and under both optimal and sub-optimal conditions. The lack of pathogen proliferation and dispersal meets the requirements of the ABPR for the storage of fallen stock. Therefore, it is recommended that the regulations are updated to include bioreduction for both pig and sheep carcasses.


Original languageEnglish
Awarding Institution
Thesis sponsors
  • BPEX
Award dateJan 2012