Nofima reports

Rapport/Report 33/2016 – English summary

Ytrestøyl, Trine; Aas, Turid Synnøve; Nerdal, Kristin Skei; Berge, Gerd Marit

Publication details

Publisher: Nofima AS

Issue: 33/2016

Number of pages: 32

International Standard Numbers:
Printed: 978-82-8296-408-1

Open Access: green


Sludge from three land based commercial smolt producing facilities in Norway were collected on a monthly basis during one year. One of the facilities was a recirculating facility (RAS) and two were flow through (FT) facilities. Samples of sludge were taken after dewatering on a belt filter and after treatment in a composting reactor (Global Enviro) originally developed for treatment of household waste. The results show that the sludge contained relatively large amounts of energy, fat and nitrogen, on average 20 MJ/kg, 5-7% and 14-18% respectively, on a dry matter basis. This indicated that there was a considerable amount of feed in the sludge. On average, 50% of the sludge was waste feed. There was some variation during the year in both macronutrients and minerals, but there were no major differences between the smolt facilities in the project. The content of the metals zink and cadmium poses some restrictions on the use of the sludge as fertilizer, whereas the content of PCBs and chlorinated pesticides was below the limits for restricted use.