Submitted to: Compost Science and Utilization
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/19/2003
Publication Date: 4/15/2005
Citation: Adler, P.R., Sikora, L.J. 2005. Mesophilic composting of arctic char manure. Compost Science and Utilization 13 (1):34-42.. Interpretive Summary: Currently manure from fish grown in raceway systems is settled and stored in basins. During storage, phosphorus and other nutrients are continually released from the manure into the surrounding water in the basin. Because of how manure is managed on farms, water flows through these basins daily carrying these released nutrients to surface water. Procedures were developed for a layered compost system in this study allowing the manure to be stored on land after it has been settled in the basins, greatly reducing the potential discharge of phosphorus to surface waters. It is a less resource intense system than standard composting technology and is a practical technology that could be readily adopted on fish farms using current equipment.
Technical Abstract: Manure in coldwater aquaculture systems is typically stored in off-line settling basins where water from the raceways continuously flows through the basin. As the water passes through the basins, the solids settle out and the excess water is discharged to surface water. Since the basins are not frequently emptied, the organic solids mineralize and nutrients flow out of the basins with the surface water discharge. Field plots were established with 2 carbon (C) sources (wheat straw or oak sawdust). Manure was applied at a rate of about 1cm/week of arctic char manure (7-8% solids) using a vacuum tank spreader modified for side discharge over the plots. The open and porous structure of wheat straw resulted in several advantages over the oak sawdust; there was not runoff during application, aerobic conditions were maintained, lower amounts of C were needed, and less time was needed to reach maturity, since decomposition rates were higher. Mineralization and nitrification rates were higher with wheat straw and although the total of phosphorus (P) content was about 2 times higher, water-extractable P was similar and did not increase as the organic matter decomposed. In contrast to thermophilic compost, N was conserved during this mesophilic composting process. A layered mesophilic compost system may be a viable manure management system to store manure on land and replace off-line settling basins for fish farmers. In this system, solids would continue to be settled in the off-line settling basins but pumped onto straw nearby for storage and stabilization.