Nutrient Recovery From Agricultural Biogas Systems

Digestate is an important element of any anaerobic digestion facility and many agricultural practices highly value these readily available nutrients. This Seabreeze Farms Case Study on Nutrient Recovery From On-Farm Biogas Systems presents the results from a research project that sets out to answer two key questions that provide an insight into the environmental benefits of a nutrient recovery system.

  • How does biogas and nutrient recovery affect methane emissions from digestate?
  • What are the implications for nutrient management?

The research project, funded by Agriculture and Agri-Food Canada and FortisBC through the Bioproducts Agri-Science Cluster with in-kind support from CH Four Biogas, analyzed the Trident nutrient recovery system that separates digestate into three fractions. Coarse fibrous solids are used for animal bedding, and the liquid digestate is converted to a nutrient-rich solid “cake” and a liquid “tea” using a combination dissolved air flotation (DAF) system and moving disk (MD) press. The “cake” can easily be transported to more distant land-base and the “tea” is used to fertigate crops located on or nearer to the farm site.

The case study summarizes findings to these questions and puts the process into perspective by considering this farm specific application, the farmer’s experience, and how to best apply this to other farms.