Passively Aerated Layered Composting of Salmon Farm Mortalities

Abstract

ABSTRACT A modified version of the static pile method of composting was used for the composting of whole salmon mortalities in a wooden, uninsulated vertical reactor measuring 0.9m X 0.9m. A perforated pipe installed perpendicular to the steel mesh base of the reactor provided passive aeration. The whole salmon were equally divided into three layers sandwiched between four equal layers of sawdust. The mean temperature reached 55°C on day 17 and remained above this for two weeks, thereby satisfying regulatory requirements. Comparison with earlier forced aeration studies made on the basis of volatile fatty acid content revealed no significant differences between the two composts at five months of age. However, the difference between the carbon to nitrogen ratio of the two was significant. The passive aeration compost had higher nitrogen content than those with forced aeration, and therefore was considered to be a better quality compost. The conclusion drawn from the study is that forced aeration is not nece...