Effect of anaerobic digestate fuel pellet production on Enterobacteriaceae and Salmonella persistence
Date
2022-07-07
Journal Title
Journal ISSN
Volume Title
Publisher
Wiley
Abstract
Production of digestate pellets for fuel has been identified as a promising circular
economy approach to provide renewable energy and additional income to
farms, while at the same time presenting the potential to divert raw digestate
from nutrient-saturated
land and reduce the risk to water quality. Although
previous research has investigated the feasibility of pellet production, there
has been little focus on the bio-safety
aspects of the system. Little is currently
known about the persistence of bacteria present in the digestate and the potential
impacts on human health for those handling this product. The aim of
the present research was to determine the effect that each step in the pellet
production process has on bacteria numbers: anaerobic digestion, mechanical
separation, solid drying, and pelletisation. Enterobacteriaceae enumeration
by colony count method was used to quantify bacteria, and the presence of
Salmonella at each stage was determined. The Enterobacteriaceae count reduced
with each stage, and the final pelletisation step reduced bacteria numbers
to below detectable levels (<10 colony forming units/g). Salmonella was
only detected in the starting slurry and absent from digestate onwards. Storage
of the pellets under winter and simulated summer conditions showed no reactivation
of Enterobacteriaceae over time. The pelletisation process produces a
digestate product with Enterobacteriaceae counts below the maximum threshold
(PAS110 specification) for transport off the source farm, but care must still
be taken when handling digestate pellets as complete sterilisation has not been
confirmed.
Description
Publication history: Accepted - 10 June 2022; Published online - 7 July 2022.
item.page.type
Article
item.page.format
Keywords
anaerobic digestion, animal by-products, digestate, Enterobacteriaceae, fuel pellet, mechanical separation, phosphorus
Citation
Cathcart, A., Smyth, B.M., Forbes, C., Lyons, G., Murray, S.T., Rooney, D. and Johnston, C.R. (2022) ‘Effect of anaerobic digestate fuel pellet production on Enterobacteriaceae and Salmonella persistence’, GCB Bioenergy. Wiley. doi:10.1111/gcbb.12986.