Review of Two Mechanical Separation Technologies for the Sustainable Management of Agricultural Phosphorus in Nutrient-Vulnerable Zones

Gary A. Lyons*, Ashley Cathcart, J. Peter Frost, Michael Wills, Christopher Johnston, Rachael Ramsey, Beatrice Smyth

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

17 Citations (Scopus)
102 Downloads (Pure)


This work reviews two mechanical separation technologies (screw press and decanting centrifuge) which could be used in the dairy, beef, pig and anaerobic digestion sectors in nutrient-vulnerable zones in order to improve the sustainability of manure and anaerobic digestate management by decreasing agricultural phosphorus loss and reducing environmental impact on water quality. Capital and operating costs, separation efficiency and throughput, and management and processing of separated fractions, including transport costs, environmental impacts and the biose-curity of separated solids for export, were considered. Of the two technologies reviewed, screw press separation is a more cost-effective option (5-fold cheaper per tonne of feedstock) when lower amounts of export of phosphorus off farm are acceptable. For farms and those with anaerobic di-gesters managing larger volumes of manure/digestate, screw press separation is possible. However if higher levels of phosphorus removal are required, the use of decanting centrifugation is a viable option. Centralised processing facilities could also make use of decanting centrifuge technology to act as processing hubs for local farms within a distance that makes it economical for transport of manure/treated manure to/from the processor (the maximum distance for economical transport of raw manure and separated solids is approximately 70 km and 84 km, respectively). Both separation technologies could be integrated into agricultural manure and digestate management systems in order to provide a more sustainable approach to managing agricultural phosphorus loss and its associated impact on water quality. Screw press and decanting centrifuge separation could reduce phosphorous loss to water bodies by 34% and from 30 to 93%, respectively.

Original languageEnglish
Article number836
Number of pages25
Issue number5
Publication statusPublished - 23 Apr 2021

Bibliographical note

Funding Information:
Funding: The authors wish to acknowledge support from the Department of Agriculture, Environment and Rural Affairs for Northern Ireland for funding Evidence and Innovation Project 18-04-01.

Funding Information:
Acknowledgments: The Bryden Centre project is supported by the European Union INTERREG VA Programme, managed by the Special EU Programmes Body (SEUPB). The views and opinions expressed in this paper do not necessarily reflect those of the European Commission or the SEUPB.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Copyright 2021 Elsevier B.V., All rights reserved.


  • Digestate
  • Manure
  • Mechanical separation
  • Phosphorus
  • Water quality

ASJC Scopus subject areas

  • Agronomy and Crop Science


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